Changing compression ona built motor

Hey all,,, I recently acquired a 383 stroker to go in my Hot rod and it is supposed to have 11.5:1 ratio compression,,,, from what I understand it's not a good idea to run pump gas with the compression that high on steel heads,,, it is a running motor and I don't want to tear it down unless I have to but I'm okay with doing that,,,
I'd like to lower the compression to 10:1 and run normal pump gas without octane booster.
So any input on how to build a 383 with the existing parts I have now and what would need to be changed is greatly appreciated,

Here's what I can tell you about the motor,,,, if you need more let me know and I'll do my best to get it.

Good ole 10/20 block,

Scat crank with I believe 3.75 stroke,
5.7 Scat rods,
Dart Iron Eagle 72 CC heads,
Roller tip 1.6 rocker arms,,, steel stamped
12-292 cam,,, 501 lift I think and 110 lobe separation,,,, need to look up more on this one.

Domed piston but I could not get the dome CC,

Holley 750 double pump vacuum secondary carb,
Not sure of the intake but it's definitely not a street intake,,, single plain high rise,,, probably Edelbrock,

Oaky that's all I can think of at the moment.

Quote:

---

Originally Posted by HotRodN

Hey all,,, I recently acquired a 383 stroker to go in my Hot rod and it is supposed to have 11.5:1 ratio compression,,,, from what I understand it's not a good idea to run pump gas with the compression that high on steel heads,,, it is a running motor and I don't want to tear it down unless I have to but I'm okay with doing that,,,
I'd like to lower the compression to 10:1 and run normal pump gas without octane booster.
So any input on how to build a 383 with the existing parts I have now and what would need to be changed is greatly appreciated,

Here's what I can tell you about the motor,,,, if you need more let me know and I'll do my best to get it.

Good ole 10/20 block,

Scat crank with I believe 3.75 stroke,
5.7 Scat rods,
Dart Iron Eagle 72 CC heads,
Roller tip 1.6 rocker arms,,, steel stamped
12-292 cam,,, 501 lift I think and 110 lobe separation,,,, need to look up more on this one.

Domed piston but I could not get the dome CC,

Holley 750 double pump vacuum secondary carb,
Not sure of the intake but it's definitely not a street intake,,, single plain high rise,,, probably Edelbrock,

Oaky that's all I can think of at the moment.

---

Since it's running, warm it to operating temperature and do a compression test on all cylinders.
Remove the air filter element.
Remove all spark plugs to help the starter turn the crank.
Disable the ignition system to prevent a fire.
Wire the primary throttle blades wide open so the motor can breathe.
Let the motor have at least 5 "chuffs" on the gauge for each cylinder. Max the needle and write it down.
https://www.youtube.com/watch?v=X_tbksFYhl4

Crane Cams engineers state that an internal combustion engine can safely be operated on pump gas up to about 165 psi cylinder pressure, although I have witnessed many motors that have more cylinder pressure than that and operate OK on pump gas. I suspect that it has to do with squish/quench.

I know you didn't ask for a lesson, but here's one anyway.
As the piston ascends in the bore and approaches top dead center, the area of the piston opposite the chamber gets friendly with the flat area of the cylinder head opposite the chamber and squishes out the air/fuel mixture that is between the piston and the head. This sudden close proximity jets the mixture across the chamber toward the spark plug and the turbulence created homogenizes the mixture so that all of it will burn, instead of having rich and lean pockets that may or may not burn.

The quench part of squish/quench occurs with the piston in very close proximity to the underside of the cylinder head, where heat is released from the piston crown into the relatively cooler cylinder head, cooling the piston. The tighter the squish/quench, the more power the motor will make, up to the point where you have a collision between the piston and the head. On a small block, David Vizard has gone as tight as, I believe 0.027" before he encountered a kiss. A kiss might be defined as seeing the piston part number imprinted on the underside of the head at the next tear-down. :eek:

.

Tech,,, measured the compression across all cylinders and it ranges from 212 to 218.
now what lol

Quote:

---

Originally Posted by HotRodN

Tech,,, measured the compression across all cylinders and it ranges from 212 to 218.
now what lol

---

Holy crap! :eek: :whacked:
Can you hear the motor detonating? What fuel did the original owner use in the motor? What fuel have you used in the motor?
It is possible that it is not detonating if the builder engineered in a very tight squish when he built it. (0.035").
If the motor is detonating on premium pump gas, the cheapest way to lower the static compression ratio is by changing pistons. Are you up for that?
A 12cc dished piston would put the static compression ratio at about 9.5:1 SCR, perfect for iron heads on pump gas, as long as you use a tight squish.

.

Hey Tech,
It was built just for drag racing and I have no idea what the squish or deck height was set at. Will certainly find out when I tear it down. To make sure I understand what you call squish,,, I'm thinking the gap between the top of the piston and the chamber in the head. Is that correct??

I've run high octane with 108 boost mixed in (a lot of it, like two cups to 2 gallons) and only ran it a few minutes total in 1 minute intervals. I couldn't hear any detonation going on best I could tell. One other thing I noticed when I pulled the plugs was they had oil on them which may have contributed to the high compression. No doubt this thing is a beast with the 750 carb compared to the 670 I first tested it with.

When I did the compression test the carb was wide open front and back as it's mechanical secondary's not vacuum. Let it turn until it stabilized on pressure which was 5 or 6 chuffs. Of course I was shocked at the amount of compression on the first cylinder when I saw it. I thought,,, man no way,,, I've never seen that much compression on any motor,,, but' I've only assembled low end rebuilds.

I'm definitely up to changing out the pistons and feel it's the best thing to do at the moment. I have no desire to have a 500+ HP motor in my street rod.
I've read one of your other posts on squish and setting up deck height etc. Great info. When I tear it down those measurements will be taken and posted for input.

Will also get one of the books you mention by David.

If you could,,, give me a component list for what combination would get me the 400HP I'm wanting to end up with on this engine. Of course I'd like to keep as much of these original parts as I can (budget on less work hours LOL). The rod's, cam, heads etc.

Had already planned on changing the intake to a Endurashine Air Gap and running the 670 carb (or 750 with vacuum secondary's if I had to) for performance.

Of course if it all gets to be way too much then I can always keep the Vortec head motor with 3 Rochester carbs in the car. But that one wouldn't give me the fun factor I don't think. My concern with that setup is the motor would choke out if I hit the carbs wide open from dumping too much fuel. I've also had problems getting it to idle or run without the choke partly closed. It's starving for fuel and I'm almost convinced the idle mixture holes need to be opened up a tad more. Three deuces look cool but are a pain to get tuned just right IMHO.

Hey this is all fun stuff for me and I'm having a ball doing it,,,, can't keep a girl friend though ha ha ha. They all say it's not just a hobby but an obsession,,, they may be right :)

Later guy's,
HotRodN

With 72cc heads, about the only way to get to 11.5-1 compression is with domed pistons. It you want to get by really cheap, pull the motor apart, find someone with a milling machine, and lop the domes off the pistons. Just make sure you measure the thickness of the dome area to make sure you're gonna have some left when you're done.

Quote:

---

Originally Posted by HotRodN

Hey Tech,
It was built just for drag racing and I have no idea what the squish or deck height was set at. Will certainly find out when I tear it down. To make sure I understand what you call squish,,, I'm thinking the gap between the top of the piston and the chamber in the head. Is that correct??

---

Yes, exactly. It is the sum of the piston deck height and the gasket thickness. For instance, a piston deck height of 0.022" added to a compressed gasket thickness of 0.020" would yield a squish/quench of 0.042".

Quote:

---

Originally Posted by HotRodN

One other thing I noticed when I pulled the plugs was they had oil on them which may have contributed to the high compression. No doubt this thing is a beast with the 750 carb compared to the 670 I first tested it with.

---

You could be right about the oil sealing the rings better. That's the difference between a dry test and a wet test.
As far as where did the oil come from, 2 possibilities come to mind right away, valve seals or the intake gaskets not sealing. When a fellow builds a motor, he should have the machine shop cut the block decks at 90 degrees square from each other. If they are not square, then the heads will not sit squarely on the block and the intake manifold will not sit squarely on the heads. If the intake gaskets do not seal, that leaves a pathway for oily vapors from the crankcase to be pulled into the cylinders when the intake valve is open. You know how you find a vacuum leak with a flammable substance, for instance spraying ether around the motor, well that won't work if the gap is on the bottom side of the gasket. I hope I'm explaining this so that you can understand it. The top side of the gasket could be tight and you wouldn't find a breach with a flammable substance, but the bottom side of the gasket being open would allow the motor to draw in oily vapors from the crankcase. This breach could be caused by someone in the past whittling on the block or heads or even the intake manifold and not making sure that everything was cut so that the whole mess was sealed up. Your machinist will have formulas for cutting different parts to make them parallel and make them fit.

Quote:

---

Originally Posted by HotRodN

I've never seen that much compression on any motor,,,

---

Neither have I, not on any of the street motors I ever put together. Of course, I always built for pump gas.

Quote:

---

Originally Posted by HotRodN

I'm definitely up to changing out the pistons and feel it's the best thing to do at the moment. I have no desire to have a 500+ HP motor in my street rod.
I've read one of your other posts on squish and setting up deck height etc. Great info. When I tear it down those measurements will be taken and posted for input.

---

Well see, here's the problem. I don't put a lot of confidence in Dart Iron Eagle heads and feel that even if you got the SCR down to a sustainable number, the motor wouldn't make the power that it could with a good set of heads. These heads were cast in 165cc intake runners, 180's, 200's, 215's and 230's, none of which impress me much. Most of them will make less or about the same flow as a set of cast iron production L31 Vortec Chevy heads, which isn't really much to write home about. You will not make 400 hp with a set of L31 heads on a 383. If you have to keep the Iron Eagle heads, then you have to keep them, but don't expect all that much from them.

Quote:

---

Originally Posted by HotRodN

Will also get one of the books you mention by David.

---

Buy used to save a few shekels....
Here's a very elementary offering by David....
http://www.amazon.com/gp/offer-listi...s=david+vizard
And a more advanced offering....
Amazon.com: Buying Choices: David Vizard's How to Build Max Performance Chevy Small Blocks on a Budget (Performance How-To)
He has published scores of books that you may want to read eventually.

Quote:

---

Originally Posted by HotRodN

If you could,,, give me a component list for what combination would get me the 400HP I'm wanting to end up with on this engine. Of course I'd like to keep as much of these original parts as I can (budget on less work hours LOL). The rod's, cam, heads etc.

---

Well, see, there we are again with those heads that I don't like very much. We need to settle that problem before I suggest a complete build for you, because I'm pretty sure you would be disappointed with the build if you have to use the Iron Eagle heads. I would like to see you do the build with a set of Pro-Filer 195's, but don't know if you can pop for the $1100 price tag. These heads will support 500 hp and 500 ft/lbs of torque on a 383 and it would be a walk in the park to put a 400 hp example together, although I'm pretty sure you'd like 500 hp better.
SBC 23 Degree Cylinder Heads

Quote:

---

Originally Posted by HotRodN

Had already planned on changing the intake to a Endurashine Air Gap and running the 670 carb (or 750 with vacuum secondary's if I had to) for performance.

---

Don't get suckered in by the marketing hype of the Air Gap intake. Some fellows who live in colder climes tell me that they have driveability problems with the manifold due to cold air working its way around the runners and that they wish they had used the standard Performer RPM. You can use any carburetor you want to, but the 750 will make the most power. Use vacuum secondaries if the converter stalls at less than 3000 rpm's or a double pumper if the converter stalls at 3000 or higher.

Quote:

---

Originally Posted by HotRodN

My concern with that setup is the motor would choke out if I hit the carbs wide open from dumping too much fuel.

---

Never happen.

Quote:

---

Originally Posted by HotRodN

I've also had problems getting it to idle or run without the choke partly closed. It's starving for fuel and I'm almost convinced the idle mixture holes need to be opened up a tad more. Three deuces look cool but are a pain to get tuned just right IMHO.

---

You just need to find a good reference book and study the carbs. Learn exactly how they operate and what you have to do to make them work properly.

Quote:

---

Originally Posted by HotRodN

Hey this is all fun stuff for me and I'm having a ball doing it,,,, can't keep a girl friend though ha ha ha. They all say it's not just a hobby but an obsession,,, they may be right :)

---

You're lookin' for love in all the wrong places. Go to the dragstrip and hang out.

.

TDK, being a machinist by trade and having access to a manual mill I've thought about fly cutting the piston tops to lower compression. These are BTW domed pistons,,,, just don't have the info on what the CC of the domes are. I believe we have an electronic thickness age at work and would verify the thickness before cutting them. Having read Tech's post it too is a option I'm considering. Having the input on components makes building the engine type I'm after a breeze. This may seem wishy washy but I'm still pondering just what engine I want in the car. Mild to wild,,,, at lest I have those options to choose from LOL.

Hey Tech,
Thanks for getting back on here and posting.
I'm familiar with the idea of a gap being in the valve train valley,,,, just wish there was a way to get either in there to test for leaks. One time I did squirt some in the valve cover to see if it made a difference but nothing happened At least nothing blew up in my face LOL.

Now as for changing out the heads I'm not opposed to doing that either. I could sell the Dart heads for something and recoup a little of the cost. I'll be looking tomorrow for a number on them to see can I identify the intake runner.

I once had a Patriot head and a Pro-Comp (I think it was) flow tested and the dude was surprised at how well the Patriot head flowed and it did better than the other all across the board.

As for the air gap,,, being in the southern part of Texas (near Houston) we don't see a lot of real cold down here but your advise will be taken. I do have a Performer RPM as well from another motor I could pull and use.

As for the love thing,,, it may be looking up LOL,,, met a lady who really likes NASCAR and probably knows more than I do. But it's all in the first date stages so I'll have to see how that goes. At least I was invited to attend the race with her and friends next weekend so I must have passed some of the "He's an okay guy test" over the weekend :)))

So I'll keep pondering all this and come up with a decision soon so I can move forward with the build. There is still plenty of other thing's to do but prefer to get one thing completed before moving on to another section.

Tech,
One thing I haven't mentioned is what car the motor will go in,,, I'm building a 32 three window coupe that' a fiberglass body and estimate the total up weight to be 2400 to 2600 depending. Just FYI,,,

I never heard of a double pump vacume secondary Holley carb

For an engine to be reliably driven on the street-I would sell this one and build another with a block set up for hydraulic roller lifters and alum heads-

Yea been thinking along those lines. But was just going to sell off what I wouldn't use and get what was needed. Again what I'd like to have is 400 crank HP. Sooo,,, if it can be done that way pass on how you'd change this one up,,,, Later Cuz,
HotRodN

The reason for keeping what could be used is because getting a block,,, having the machine work done to convert to 383 and all the other parts. I would have way more in it than what I paid for this engine. Just think it's wise to use what you can from this build and scrap the rest.

Having a block that is set up for OEM type hyd roller lifters is a valuble part of the scheme to just sell what you have and build whats best-by the time you get different pistons/rings/pins, balalance them to crank, etc-buy heads and valve train, you can sell what you have as an assembly and build a much more street suitable set up for todays gas

HotRonN, if your 383 is an older (pre-'87) block you can convert it to hydraulic roller lifters instead of selling it and starting over. Here's one of several articles that walk through the process - Converting a Hydraulic-Roller Camshaft - Tech Article - Chevy High Performance Magazine Being able to do your own machine work is a huge plus, so IMO the approach is to go through the engine you have and map out a detailed plan for everything you'll need to do to pull down your compression, improve your volumetric air flow, and ensure reliability with a roller cam. Once you have the plan, big parts down to nuts, bolts, gaskets and all of the machining you can put numbers against your shopping list and make an informed decision. Tech's one of the most down to earth, no BS sources for questions that come up about pieces & parts that you'll need, IMO. If the numbers don't pan out after you have the plan, then sell the whole shebang and start out with a later model, OEM roller cam block like Jerry is suggesting, or shop Chevy Performance and buy one from GM that's ready to roll, and comes with warranty.

Hey Roger,
Yes Sir,,, I agree Tech has some very good insight and I don't mind the being direct at all,,, actually prefer getting to the nuts and bolts of things to put it simply. Read the article and found it very interesting and makes a really good case for a later model roller block. And with all that,,, it's also pushing me more toward and LS engine,,, just pondering it though at the moment. What caught me most was the end play or shift of the cam on a roller and the .005" tolerance. I'd do a carb intake and only have the ECM for ignition. I'm just not real sure I like having the coil packs hanging on the valve covers. Kind of takes away from the bling of shiny valve covers LOL. Not having to deal with the distributor next to the firewall is an advantage. There is still room to do a swap if I decide to before completing the build. One area I can't picture on doing an LS install is the accessory mounting and if the water pump would get in the way of the radiator fan which isn't mounted at the moment so I could be concerned over nothing.

I am a machinist by trade just not a automotive machinist,,, I make energy related parts which can be much more complicated. Would love to get into some engine machine work though.

Quote:

---

Originally Posted by jerry clayton

Having a block that is set up for OEM type hyd roller lifters is a valuble part of the scheme to just sell what you have and build whats best-by the time you get different pistons/rings/pins, balalance them to crank, etc-buy heads and valve train, you can sell what you have as an assembly and build a much more street suitable set up for todays gas

---

So Jerry,,,, I read the article Roger linked to and am considering your suggestion. Could you recommend a year model range of good blocks to use. I'm looking online for deals but haven't some across one yet I'd consider. Of course nothing happens until I sell what I have LOL... Not a high roller over here,,, dang it,,,, Where's Jay Leno when you need him

Here's a tutorial that was written about the L31 cylinder heads, which bolt onto the L31 5700 Vortec motor that Chevy used in trucks and vans from '96 to '02. It was still the Gen I architecture, but featured a roller cam and one-piece rear seal stock from the factory. The vehicles that used it are listed in the article.
http://www.crankshaftcoalition.com/w..._cylinder_head

Gen II motors (LT1) also came with roller cams and one-piece seals, '92 to '97 I believe, with a reverse cooling system where the heads got the cool water first. Aluminum heads on F body cars. These heads will not work on Gen I motors without considerable jumping through hoops.

Gen III motors (LS1), a return to conventional cooling. Aluminum block and heads.

.

Hey Tech,,, hope you get to see this post. I've sold the motor so I'm ready for that wish list to build a simple yet nice 383. I'm looking for 375 to 450 HP that will be slightly economical to operate on pump gas and not break the bank building. There are completed motors out there but I'd prefer to know what's really in it.
I'm also looking at the possibility of doing a 5.7 or 6.0 LS swap that would be carbureted instead of fuel injected. Seems the younger crowd really likes the LS and since I "MAY" sell the car sometime down the road figured it may be wise to consider the type of people who would be buying. Not too many of us really old farts left LOL. Besides,,, from all I've read and talked with others about the LS,,, the bottom end is pretty fool prof and you can get the HP I'm looking for pretty easy. I also like the no distributor thing as it will let me get the engine a little closer to the firewall.

So guy's,,, jump in with all the input you have,,, I'm all ears LOL

If your just looking to get it a little closer to the fire wall???Put a Ford in it!!!!!!!


Or consider LT1 series engine

Ha ha,,, Yea a Ford in a Ford,,, didn't I read about that someplace lol

Oh boy! I love a new engine build. I’ve been watching this thread and now feel like I can really jump in and hopefully, offer some advice that you can digest and use what you believe to be appropriate.

I’ve posted this information several times, but it’s easier to update it and share again so you don’t have to search for it. I have used variations of this combination for a lot of years. It’s proven and should net you well over 450 horsepower and 460 plus foot pounds of torque.

First and foremost – find a good machine shop where you can talk to the person who will be doing the work. The prep on your block is critical. The stroker motor can be a screamer if built correctly, but heaven help you if clearances are not correct as the whole thing will come apart and you’ll have one very expensive door stop! Make sure that the technician has built many 383 motors. I know everyone has to learn somewhere – but you don’t want it to be your engine. As an option, Summit sells a block that has been all prepped for a 383 build for $700 plus another $100 for delivery. I have never used a Summit prepped block as the supply of bone yard engines has always been pretty good wherever I have lived; however, you may want to compare and price. Ordering the block from Summit will get you a nice clean unit, but I’d still want to check everything out – your call.

That said and if you go a complete build route where you start with a used block, have the block cleaned and tested – no need to build a block that has cracks or cannot be squared. Make sure that the machine shop understands that you’ll be building a 383 stroker so you want to have the crank journals align bored. In most builds, I ask the machine shop square the block and cut it to 9.003” – this is an important measurement as detailed a bit later on.

Have the machine shop install new cam bearings and new brass freeze plugs. Also have the machinist go over the location of all the galley plugs with you so you know where they are and that they have been properly installed. When you get the block back from the machine shop make sure you really scrub that baby down with hot soapy water. I like Dawn dish washing liquid and water straight from the bottom of the water heater. Put the block on the engine stand and dry with compressed air really well. Paint the inside of the engine with Glyptal. Its $50 a quart from Eastwood – buy the brush on and a quart will do the job real nice. I buy the China bristle 2” brushes from Harbor freight by the box. They come in handy and are throw-away items. Make sure you fan the loose bristles out before starting to paint. Also paint the exterior at this time too. I use rattle can paint from VHT and have for years. Let everything dry real well – at least 48 hours.

Rotating assemblies are really your choice. I’ve used Eagle cranks and had good success – some here think they’re junk and will tell you so. If you like Scat, that’s fine too. The nice thing about a kit from a top tier company is that you can get the crank, bearings, rod, bolts (and pistons and rings) in one package that should increase the likelihood of everything fitting nicely together. Again, some will differ – but I have used the kits from Eagle, some from Scat and years ago, from PAW (their “in-house” kit) and had good luck. I still check everything with a micrometer but I’ve rarely had to return anything. I have had Summit send me replacement head bolts for free one time when I had an issue. I find if I ask nicely when I have had issues (again, very few) I usually get good support and service.

Back to build – I’ve used a -7cc flat top and with the above deck height (remember that 9.003” measurement?) and that keeps things in the 10-10.5:1 compression ratio with a .041 head gasket (see below for part number). A -12 piston will certainly lower your compression ratio into the 9’s, but IMO - this could cost you some horsepower. You will need to match final hone/size to pistons and press the pistons and rods together – it’s a bit tricky if you’ve not done it a lot and you need a press so this is another machine shop task that’s worth spending a few extra dollars for.

It is real easy to overlook the oil pan assembly. You can go stock, but need to be mindful of clearances here as well. I like the Milodon 30901 as it holds 7 quarts and fits stroker motors – might need a bit of adjustment with Eagle or Scat rods so be sure and check. Use Milodon 18750 oil pump with the 18314 pickup. Use Milodon 23050 oil pump drive shaft and 41000 one piece gasket. Milodon 81300 is an oil pan stud bolt kit – and, in my opinion, worth the $20 for ease of assembly. Many do not like the one piece gasket - especially when working on the engine in the car, but I have found them to be fine – a word of caution – do not overtighten as that’s where most of the leak problems come from. GM torques them to 12 ft/lbs at the factory. Never go more than 15 ft/lbs. I even use a ¼” torque wrench as is helps remind me to do pan bolts very gently. Timing cover is half – i.e., 6-7 ft/lbs.

Top the engine off with the components listed below:
I really do like AFR 195 heads and think they may be good for +/- 25-50 horsepower. Whatever you do, stay away from the Dart 127122 heads – they are less money but have a lot of issues.
Double roller timing set - Summit is fine
Comp Cams 7972-16 chrome moly 5/16-inch pushrods
Comp Cams Magnum Steel Roller Tip Rocker Arms 1417-16 – these are a 1.52 roller tip. Optionally the Comp Cams 1305-16 Pro Magnum Roller rockers are full roller rockers in a 1.60 ratio.
Comp Cams K08-420-8 - Comp Cams Xtreme Energy hydraulic roller - kit with lifters
Depending on the block you get, you may also need a Comp Cams 08-100 lifter install kit that has the spider, lifter guides and camshaft retainer (must have this to keep the cam in place).

There’s a couple ways to go on carburation – my all-time favorite is a combination Edelbrock Performer RPM and a 750cfm Quadrajet. The Demon 5402010 Mighty Demon 850 Carburetor (I have not yet used one, but like the looks and tech specs of the new Quick Fuel carbs, but they are expensive ($6-700) should pair well with the Performer RPM as well, but I have not personally vetted this combination.

Fel-Pro 1205 intake manifold gasket
Fel-Pro 1003 head gasket
HEI Ignition - stock Chevy is a good unit - pair with a MSD ignition (stay away from Accel anything – I’ve never had good luck with Accel and they’re no cheaper than MSD which has always been good to me.)

I’d go with 3.40 (or taller) rear end and a 2500 RPM stall converter if you’re going to run an automatic.


Good Luck,
Glenn

Glenn has put together a good combination of parts, now I'll have a go at it....

First, choose the piston compression height that you will use. 383 pistons for 6" rods can be had with compression heights from 1.125" to 1.133", so you have to coordinate the rod length with the piston compression height and crank radius to arrive at a measured stack of parts. Only then will you know what block deck height to use with what head gasket in order to set the squish/quench to somewhere between 0.035" and 0.045" (thirty five thousandths to forty five thousandths).

If I were going to build a Gen I 383 for the street today, a motor that would run on available pump gas without detonation, here's how I would do it.....

Keith Black KB122-030 pistons...(1.130" compression height)
Keith Black KB Performance Pistons KB122-030 - Free Shipping on Orders Over $99 at Summit Racing
Use 1/16" rings of your choice. Ductile iron moly ring set 4000BD8, Cast iron moly ring set 4000BM8.
You must pay particular attention to the top ring end gap with these pistons. Follow the instructions that come with them.

Scat 2-IRC-6000P 6" rods...
Scat Pro Stock I-Beam Connecting Rods 2-ICR6000P - Free Shipping on Orders Over $99 at Summit Racing
These rods are clearanced to miss the cam lobes, so you can use a standard diameter cam core.

Scat 9-350-3750-6000 3.750" cast steel crank...
Scat Series 9000 Cast Pro Comp Stroker Lightweight Crankshafts 9-350-3750-6000 - Free Shipping on Orders Over $99 at Summit Racing
This is an internally balanced rotating assembly, so budget money for final balancing with a 350 damper and 350 flexplate at the machine shop.

This will make a parts stack of 9.005", so I would cut the block decks to a new block deck height of 9.005" for a zero deck. Then I'd use a Fel-Pro 1003 head gasket that compresses to 0.041" and makes a 0.041 squish/quench with a zero-deck block. Have your machine shop index the block so that cuts are made exactly 90 degrees apart. If the block is square, then the heads will sit squarely on the block and the manifold will sit squarely on the heads and everything will seal up and be happy with each other.

I would use Pro-Filer 195cc intake runner heads, 70cc chambers for a static compression ratio of 10.1:1.
SBC 23 Degree Cylinder Heads
Under $1100 ready to bolt on...

I'd use a dual-plane, high-rise intake manifold such as the Edelbrock Performer RPM intake manifold, #7104, with a rebuilt Quadrajet carb (Cliff Ruggles is the Quadrajet guru, so try to buy one of his rebuilts if you can).
Cliffs High Performance Quadrajets :: Qjet Carburetor Rebuild Kits, Parts, Quadrajet Rebuilding, Quadrajet Parts, Bushing Kits, Carb Tuning
I would not use an Air Gap manifold due to driveability issues in colder climates. There is only a couple of hp difference between the standard RPM and the Air Gap RPM. You'd never feel the difference in hp in the seat of your pants, but you'll sure be able to tell the difference in driveability issues.

I like a Milodon 7-quart oil pan with Milodon oil pump. Position the pick-up screen 3/8" to 1/2" from the bottom of the pan. Use modeling clay on the oil pump pickup and ease the pan down to mash the clay and find the clearance. Do not use Play-Doh, it will not hold its shape. Use oil-based modeling clay from a hobby shop or craft store. If the pickup is too far from the pan bottom, you could run the motor out of oil. If the pickup is too close to the pan, the pump could pull the bottom of the pan up against the pickup and starve the motor of oil.

Howards retro-fit hydraulic roller cam and roller lifter kit CL111145-10
Howards Cams Retro-Fit Hydraulic Roller Camshaft and Lifter Kits CL111145-10 - Free Shipping on Orders Over $99 at Summit Racing
Use an 1800-2000 rpm stall speed torque converter.

1 5/8" long tube headers with an X or H pipe immediately after the collector, then pipes and mufflers of your choice (2 1/4" to 2 1/2" pipes) to the rear bumper. Terminating the pipes under the vehicle smacks of Mickey Mouse and is a pain to drive with the sheet metal reverberating.

Use a 14" x 4" air filter assembly so the motor can breathe.

I'd use a DUI distributor with Taylor wires....
Performance Distributors - Performance Distributors

Crane makes the most precise full roller rocker arms. I would not use the Comp units that use a sliding ball fulcrum.

Follow this tutorial by Scott Foxwell to get the proper pushrod geometry....
https://www.youtube.com/watch?v=o5is9BsH5OU

.

Now this is what I've been wanting to see. I've saved both lists and will got to work on obtaining prices.

Only thing I don't see is the type of block,,, meaning pre-86 or later roller block.

Thanks again guy's,,,, man ya'll gave a lot of info,,, this will tie me up for weeks ha ha ha ,,,,
HotRodN

Another question,,,,, how well do the engines built for this much HP do with long trips,,, meaning,,, are these best for drag racing or local short runs to the car show's,,, or do they also serve well for taking long road trips where endurance is important?
Something I plan on doing with the car,,,, making a few trips to other states and the related car shows and events.

Definitely go with a roller block - in my opinion, they're better all the way around. The Summit part I mentioned (SUM-1500100-30) is a 1996-2000 factory four-bolt roller cam block. For $700 it's probably a good base to start from as the block has been vetted and all the machine work has been done (I'd still scrub it clean and paint the innards with Glyptal and mic everything - but that's just me). I also have this thing about painting Chevy engines Chevy Orange if they're going to be used in a hot rod or a muscle car.

Either of these builds would be good for everything from crusin' to a long jaunt. I have several of these builds with well over 50K miles and they're purring right along. Tech's recommendations are spot on and he stays pretty current on best practice and part numbers. As you've probably noticed, we share a lot of the same component recommendations. While I have not personally used the Pro-Filer heads they look good and the price is right. As Tech recommends them I may use a set on my next build.

Pick your cam after you decide in which generation of block you're going to use. The Howard's cam is a titch more aggressive and is a retrofit roller cam for engines that did not originally come with a roller cam. I have not used this exact part but have used other Howard's products and found them to be good.

If you're going to do a lot of stoplight-to-stoplight you'll want to spend time to make sure cooling system is adequate. The stock GM clutch-type fan with a proper shroud is still one of the best ways to cool an engine - stay away from electric unless you have insurmountable clearance issues.

Don't look for good mileage but pretty much anytime you mash the pedal tires will fry and smoke will appear!

Let us know what you decide!
Glenn

I found the absolute best improvement in gas mileage for both my nomad W/ 383 and the charger W/318 is to drive my Vega W/140.

Ha ha,,, don't have a Vega but I do have a Harley that gets about 45 MPG,,,

I looked up the engine blocks on Summit website and right now they have a special going on for $629 and freight about $110,,, after reading some of the feedback I'm a bit concerned over quality. Seems quite a few customers received blocks that had a lot of rust in the cylinder bores and lifter bores. Also a few complained about dimensional tolerances. I called and talked with customer service and they have a decent return policy so will most likely go that route fro a block.

I stopped by the machine shop I normally use and was surprised with the answers I got from one of the owners about the machine work they do. Seems they do not have a way to index the block when deck machining. Instead,,, they indicate the surface and then machine. The thought was if it was right from the factory it should be right now. To me,,, how do we know it hasn't been decked before and done incorrectly or that it was right from the factory. I would assume a factory never worked before block would be good unless it has a slight warp to it from over heating. Maybe I'm being a bit picky but I don't need and expensive BBQ pit or boat anchor. Also the machine work alone was more than a block from Summit,,, so,,, looks like doing the Summit way is the best for getting a block ready to go and build. Just hope IO don't have to go through several blocks to get what I'm after. I have tools to measure most dimensions except being able to check block square. I'll keep checking shop around here and see if there's a better deal or at least close before jumping off into the Summit block.

More in a few days, I'm going to start a build spreadsheet to come up with a general cost.

Thanks guy's,
HotRodN
P.S Hope you all had a great Thanksgiving !!! Give thanks to the one who gives all,,,, Amen :))

Glenn,
I looked at using a stock fan but on my car it wouldn't work because it would sit too low. I think it would be outside the bottom of the radiator. I've gone with a PRC radiator and 16" electric fan. They claim it works for up to 600 HP. I'll have to see. Even with the electric fan it's gonna be real close to the water pump shaft. But it will clear. Right now I'm trying to get happy with the final placement of the whole setup. Hard to get good measurements with the engine in place. But it's getting there. Heck it's taken me all week to get the grille shell mounted to the radiator. Keep getting interrupted and also had to make a special bracket for the top. I had the radiator made 1 inch shorter than stock so the brackets shipped with it didn't work up top. Now to get a shroud mocked up and have my buddy get one made. Will keep all up to date and post pix once this part is done.
HotRodN

Tech,
If I were to decide to go with 5.7" Rods,,, what changes,,, compression length?? I assume I'd go from 1.130" to 1.430" given the .300" difference. I also assume that torque would be slightly lower than with 6" rods.

I noticed you have Hypereutectic pistons chosen,,, would forged pistons be a slightly better choice or,,, do the hyper's perform well enough to not worry about the more expensive forged. Keep in mind this is not going to be a drag car but I will step on it occasionally for the adrenaline rush LOL.

Quote:

---

Originally Posted by HotRodN

Tech,
If I were to decide to go with 5.7" Rods,,, what changes,,, compression length?? I assume I'd go from 1.130" to 1.430" given the .300" difference. I also assume that torque would be slightly lower than with 6" rods.

---

Yes, piston compression height for the 5.7" rod will be from 1.425" to about 1.433", depending on manufacturer. Choose the piston you want to use and add the compression height of the piston to the rod length and stroke radius, just like above. That will tell you how much to cut the block decks.
My choice might be the Keith Black KB253+30. Same piston crown design as I selected for the 6" rod except the compression height is for a 5.7" rod.
https://www.uempistons.com/index.php...26e4bc2877d034
I did not choose the 6" rods for any torque advantage because I doubt there is any, I chose them for compatibility with the internal balance crankshaft. If you go with 5.7" rods, you cannot use an internal balance crank, you must use the external balance crank and balance it with a SBC 400 damper and flexplate/flywheel. The 400 damper and flexplate have an eccentric weight built into them. Again, budget a little extra cash for finish-balancing at the machine shop. It might be spot-on from the maker, but maybe not. 1.433" + 5.7" + 1.875" = 9.008", so you could cut the block decks to 9.008" for a zero deck and 0.041" squish.

Quote:

---

Originally Posted by HotRodN

I noticed you have Hypereutectic pistons chosen,,, would forged pistons be a slightly better choice or,,, do the hyper's perform well enough to not worry about the more expensive forged. Keep in mind this is not going to be a drag car but I will step on it occasionally for the adrenaline rush LOL.

---

If it were my money going into this motor, I'd choose hypers. Now, if I were going to use a blower or spray, then I'd step up to forged. If you keep the motor out of detonation, even cast pistons will work well in most cases, but I like to use hypers for a little insurance.

Quote:

---

Originally Posted by HotRodN

The thought was if it was right from the factory it should be right now.

---

You've already figured out that the block might not be dead nuts from the factory or maybe someone took a cut on the decks who didn't know what they were doing, so I think you're a little smarter than the guys at the machine shop.
NEVER ASSUME ANYTHING. CHECK EVERYTHING.
Doesn't your machine shop have a precision square? Use it with feeler gauge blades to check for 90 degree square between the banks, front, middle and rear.

.

The use of 6 inch rods will give you a much lighter piston weigh because you will remove .300 section of the piston and the additional weight of the longer rod isn't as much. With the 6 inch rod the crankshaft counterweights don't have to be relieved so much allowing for a much simpler internal balance, many times without the addition of heavy metal

I don't understand why replies I make don't always get posted,,,, must be something I'm doing.
Okay,,, I'll stick with 6" rods. Just makes sense and is easier to keep the build going as planned and save guess work. For now I'm trying to get that warm feeling about the Summit block but given the quote from a different shop even if I had to have some work done to it I'd probably still come out cheaper. Feels like the shops today are gouging prices to stay afloat with the downturn in the economy,,,, just MHO. Still don't see how Summit can sell the blocks at these prices. But hey I'm happy with it. Once I have pricing on all the parts and compare to going the LS route I'll pull the trigger.

Tech, one option to get this built cheaper for the moment could be to use the 487X heads I have on another engine until I'm ready to get the Pro-Filer heads. Things are getting tight with hours reduced so just looking at all my options. The 487X (last 3 digits) heads were used on the SBC 350' back in 70 thru 72 and I know on the Corvette motor to produce 350 HP from the factory engine. So the thought is I could at least get the 350 on a 383 build with cam until I can swing the other heads.

Tech,
We don't have a precision square at the shop and the one I have won't work for checking the block. It's not big enough, I think it's only like a 6" square. We do however have a large granite surface plate but I doubt they will let me put the block up there to check square with a height gage. But if so,, I could also check cam bore to crank bore center line. While I can still get that dimension, it's just a tad tougher using mic's and calipers. But I can get real close using just those tools.
HotRodN

just to let you know how it works---blocks are set up with a fixture that has a 2' solid bar throw adapter rings that size it to the main bore-then a center bar with centering cones is installed in the cam bore and block is centered on those two axis-there is a plate at the end that has the indicating surfaces on to measure to deck at the 45* each way------then there is a triangular piece that you can put in any cylinder against the wall and indicate to main diminsion established from the front plate.



http://www.bhjproducts.com/bhj_conte.../bt1_intro.php

http://www.bhjproducts.com/bhj_conte...tfixt/dhbe.php

http://www.bhjproducts.com/bhj_conte...ntfixt/btk.php

Quote:

---

Originally Posted by HotRodN

Tech, one option to get this built cheaper for the moment could be to use the 487X heads I have on another engine until I'm ready to get the Pro-Filer heads. Things are getting tight with hours reduced so just looking at all my options. The 487X (last 3 digits) heads were used on the SBC 350' back in 70 thru 72 and I know on the Corvette motor to produce 350 HP from the factory engine. So the thought is I could at least get the 350 on a 383 build with cam until I can swing the other heads.

---

Makes perfect sense. Go ahead and build the 383 short block with zero deck, then pop the iron heads on until you can do better. Those 487X heads have a 75cc combustion chamber, so static compression ratio would be 9.6:1. Use the same Fel-Pro 1003 head gaskets that you would use with aluminum heads, for a 0.041" squish/quench.

.

Jerry, you are the man with those links, thanks very much. The verbage in those links just verifies what I've been preaching for years....

Twisted Blocks: On a twisted block, it is necessary to choose a point on the deck surface to use as a reference
point for set-up. As a result, you may be compounding the out-of-square condition.

Uneven Deck Clearance: Deck clearance often varies between the top and bottom edges of the piston due to the
deck surface not being at 90 degrees to the bore. On race engines where deck clearances are held on the verge
of piston to head contact, any discrepancy in deck angle means lost compression.

Bores Not At 90 Degrees: Since most production lines use the pan rails as the reference point, it is common to
find the bores at angles other than the intended 45 degrees when referenced from the cam-crank centerline.

Cam and Ignition Timing Variations: If you have run into cam timing variations between cylinders on opposite
banks, it may not be the fault of the camshaft. Again, since most blocks are machined from the pan rails, the
cylinder “V” may not be at 45 degrees when referenced from each side of the cam-crank centerline.

O-Ring Groove Variations: If you are cutting O-Ring grooves on a boring stand which references from the pan
rails, it is not uncommon to have drastic depth variations.

Poor Intake Manifold Fit: This condition is usually blamed on the intake manifold. However, if the included angle
of the deck surfaces is not 90 degrees or if the top of the block has the incorrect angle, the manifold may not be
at fault. This problem is often manifested with the motor sucking oily vapors from the crankcase because the intake manifold/cylinder head sealing surface is open to the crankcase on the bottoms of the ports. If the sealing surface is open on the top, the leak can be found with ether or other combustible substance, but an open leak on the bottom of the manifold/head cannot be found with ether.

Block Deck-Height Measurements: The Blok-Tru is marked with the height from the crankshaft centerline to
index surface. A simple measurement from the block deck surface to the index surface of the Blok-Tru plate,
added to the Plate’s marked dimension gives you the deck height. This measurement can be easily made using
our Deck Height Micrometer, shown on page 8.

.

Thanks Tech----
as for the twisted deck motors-I have never found a chev block that wasn't twisted-I think it came from the blocks being broached thru a machine pushed from one end-results are consistent with the offser in the clylinders side to side where both sides surfacing doesn't start at same time-differance of the rod width offset.

The block tru plate is 7.500 inches from the crankshaft/main line center-----
those triangular bricks for measuring individual holes will set against the wall and on the center bar-just add 7.5 to your depth mike tool and you have it to prove results in all cylinders