383 500 Hp! No Juice

I'm hoping to get someones help, hopefully help from experience. I did post on this earlier, but now I have a more concrete route I want to go, to get to the 500 HP mark...no boost no juice.

500 is just a benchmark, I'd ideally like to run flat 12's in an 81 camaro,stock weight, retain decent mileage, and some reliability to drive on the weekednds 50 miles to the track on PUMP GAS

WELL, I am buying the short block from a friend. It's got 12.5:1 compression,

This block was machined 2 seasons ago very well, zero decked, I dunno what else, because HE had it done. But I know he paid an arm and a leg, had it blueprinted etc.

its obiously a 383 (actually a 385ish, bored .040 over), 5.7" rods

I will replace the pistons with forged flat tops to achieve roughly 10.0 or 10.5 compression. Can I go higher and still run pump gas?


the cam is 250.260 and .533/.555 @ .050. Not sure about lash or lsa, i'll ask him for the card on the cam if he has it. Its a solid flat tappett.

Heads are up in the air. DEFINATELY want AFR's, not sure on 195's or 210's, any suggestions?

Dart, single plane intake

holley 750 cfm , mech secondary(im assuming, havent bought one yet to replace my 650, any sugg?)


msd ignition, mech water pump, new edelbrock fuel pump (cant remember spec,more than sufficient tho)


I want to run pump fuel, no doubt. But I want to get close to 500, and YES, to pad my ego. :-). Or say, 380-400 rwhp :-).

I was thinking of using a 3200 rpm stall tc i have, but i hear i may need a higher stall?

built th-350 with shift kit

3.42 rear end, posi (not a good match with the cam?)

1 3/4" headers to 2 1/2" pipe, thru 2 flowmasters no x or h pipe

What more info can I provide? any suggestions?

Desktop Dyno shows 425 hp. seems kinda low.
How are these companies making 515 hp on 93, with afr 195's, 9.5:1 compression etc? (AFR,CHEVY HI-PERF) With a much more tame came.

thanks!


:confused: :confused: :confused:

Most engine simulators rely on a engine volumetric efficiency number to calculate hp. You need to figure out your volumetric efficiency in order to get an accurate hp prediction. Most desktop dyno's default around 80%, these other manufacturers might be able raise their VE a little. Adding boost increases the VE past 100% Don't ask me how to calculate it, I'm sure the calculations are very involved.

12.5:1 compression on pump gas? 10.5:1 is starting to get high for pump gas. Above 10.5:1, I strongly recommend computer controls for fuel and timing. You'll need a cam with a tight lobe seperation angle (more valve overlap between intake and exhaust stroke) to bleed off cylinder pressures in the lower rpms to help combat detonation. Because you'll have to run some big cam with a tight LSA to get the hp you want without detonation, you're going to be pushing a lot of fuel through the cylinder and right out the exhaust because of the amount of time both valves are open. Your fuel milage is going to be bad. Maybe 7 or 8 mpg? The car wont idle well either.

NO, HE WAS RUNNING RACING FUEL AT 12.5:1.

AS FAR AS "NOT IDLEING WELL",WHAT O U MEAN? HAVE TO GAS IT WHILE AT A STOP LIGHT?

IS THIS BASED ON THE CAM I TOLD U WAS ALREADY IN THERE?

I APPRECIATE UR RESPONSES IN THIS THREAD AS WELL AS THE OTHER.

DO U HAVE ANY RECCOMMENDATIONS AS FAR AS WHAT COMBO WOULD WORK BETTER WITH THOSE AFRS, IN THIS SHORT BLOCK (MAYBE A DIFF CAM?), STILL PUSHING THE HP TO 475+?

tHANKS AGAIN

With everything right on. The math says you can go as high as 11.35:1SCR/8.50:1DCR if the cam you have has 73*ABDC IVC.

Ruff est. 488hp @6000rpm 457Lbft @5000rpm

them #'s are with small tube headers and muffler

503hp @6500rpm 471Lbft @5000rpm large tube headers and muffers

536hp @6500rpm 487Lbft @5000rpm with large tube open headers

3.73 rear gears would give you 6500rpm @140mph with 28" tire (27 actual)

4:10 rear gear If yur trying for 127mph @6500rpm

thats my point. u say 500, i say 450, another guy says 400.

what sim software r u using?

Sounds like you are leaning towards spinning this thing pretty good. If you want to go with a 3600 stall converter, I would go with AFR 215's, change the rods to 6" units, less stress on the pistons. With the single plane intake manifold, you will lose a little in the lower RPM range, but look out on the top end.

I've been figuring the same with that cam. It aint gonna run worth a darn. What cam might u suggest? something in the 240 range with max lift?

I HAVE looked at those afr combos BUT none even come CLOSE in an EA or Desktop dyno. Wonder why?

If I end up changing pistons AND cam, I dont think I'll even be buying the short block, since it'll cost the same to have one machined to my specs with cam and pistons.

This combo will get you 11.90's in your 81 with a 3.55 rear gear and a 383

383 with 9.5 to 1 with a .005 deck ...sportsman 200cc heads 2.02-2.05 valves / cam 230 duration @ .050 with .495 lift degreed in!....7qt pan....thin oil /good pump...headers and a 2 1/2 exhaust ...and a 2500 stahl( if auto trans)

This will run all day long and idle in traffic and will run the number if you tie it good...and this runs a 10in street tire....

If you use a aluminum head and/or a roller cam or anything above and beyond what I listed will only help....especially a Asymetrical cam with slightly more lift and duration on the exhaust side if you use a smaller head....This yeilds approx 450hp

bumping the CR to 9.7 (thinner gasket) and a 240@ .050 roller cam may put you over 500-550hp but then it will dance all over the starting line.....

I might also add that 500hp with 12.5 to 1 is easily obtainable but this is racing compression ( no street use) used on the street you may very well exceed the fuel and this melts stuff (usually pistons) you can use this but you would have to severely "over cam" this to work and it wold not be responsive for a daily driver and you would be disapointed.....If this is going to see a daily grind...stay conservative you will be so happy you did....

You can run 500hp with 9.5 to 1 ALL DAy
you can run 500hp with 12.5 to 1 20 seconds at near max rpm's before cylinder pressures start exceeding the fuel!

so dr bowtie, do u speak from experience? that sounds like an easily attainable combo. Is that cam u quoted a solid flat tappet?

Would slightly more lift help (more than 495?). It seems like a mild cam to make so much power. I WILL be running ALUMINUM AFR 195's. You suggest an asymetrical cam for that?

Yes I do....That cam was a cam dynamics (crane) it's a hydrolic flat tappet....

Yes....but depends on what exactly you want to do with the combo.....all out or driver...I personally would opt for a roller cam in anything but that cost some paso's.... an Asymetrical will always get you the most power.....I only use a symetrical cam when I need to bleed off some torque to get it off the line consistantly!

Just one question. Why are you going with that gear ratio?

If you are asking me, I got the rear end from an old 79 camaro and it had the 3.42s in it, better then my 2.xx.

Id like to be able to cruise at 60 at a decent rpm, so i feared going over say 3.73's.

the motor is the major concern

I want a somewhat consistant flat 12 second car i can drive on the highway and only burn a gallon every 9 or 10 miles. I will maybe goto the track 5 or 6 times/season. thats all.

other than that, I'd like to be able to do a 100 ft burnout if i want to while going 25 and dropping it into 1st. TORQUE!

what DISADVANTAGE would come from having more lift than ur combo, Dr. Bowtie?

Fed....

That 342 rear will be fine....pick a stall converter acording to the cam....but that 3500 will do fine....

Really come on....100ft burnout @ 25mph when goin back to first? do you realize what you are saying.....

although this is practical...quite easy actually.....if you want to impress girls...well it doesn't..well maybe a little...but in a race you want it to "hook and book" if it does what you want it to your going to get spanked every time.... plus buy lot of tires....been there done that....

3rd....minimal if any as long as you don't go overboard....but lift isn't what your after..... duration is the whole key....

Hi THEFED,
The good Doctor is correct. If you can't get it to the ground there's not much sense in having it.
I don't know if it was mentioned earlier but you might think of using an overdrive tranny.
The one thing mentioned in the first post was that the block was done a couple of years ago and you are going to change the pistons. Make sure you have the correct piston to wall clearance and deck height.

i understand that doing a burnout at 25 is no good, but my point is that i want to have the torque to do so. my last rebuild was a 350 that turned out okay, ran mid-high 13's, but didnt have a lot in the torque department.

i want to break em loose, IF i choose to do so, IF i want to, I wanna be able to smoke em at will. thats all

As far as the OD tranny, I will possibly upgrade one day, but i just bought this th 350 recently, built to handle about 500 hp.also a new megashifter, so i dont wanna waste all that $$.

thanks for all ur input guys!

Fed.....

If you ran 13's with the 350 you had plenty of torque....you just got used to it....

If you want those results get an adjustable rear suspension....pinion angle is where it's at.....if you raise the angle towards the bottom of the car....even a 4 banger could roast the tires for a 100 feet....lower it towards the pavement and it WILL stick.....a 540 cu in 700hp motor would have a tough time breaking the tires.....

Do you see what I am trying to say?

My last toy was a 78 chevy 4x4 with 38's and a 400cu.in mostly stock except a minor changer and I could rip the heck out of all 4 tires in 4 high.... does no good....

i maY have gotten used to it, but 12 secs flat, and high 13's are WORLDS apart.

that 11.9 sec combo seems quite easily attainable, but seems like it wouldnt happen imho. im not calling u a liar, just that ive never seen such a combo do that.11.9 is VERY respectable.

I WILL most likely aim that direction, but going with the AFR's

You think the AFR's will help a lot?


what thickness gasket did u use in ur setup?

an asymmetrical cam,plus the afr's should produce a LITTLE more power, from what I gather.

I wouldnt mind having trouble hooking up. It's better than being disappointed u have not enough power.

SO DR BOWTIE, i just realized what the specs are in my 350 in the driveway. hydraulic summit cam, 234/244 488/510 @ 50. whats ur take on that cam?

that would be a great cam for the 383 or a 350.....I did the same test as they did in HotRod a while back and got similar results...

First I started with a complete seasoned 350 with 882 heads...these are 76cc Comb. Cham.

First we did a basic cylinder hone and added new flat top 9.5:1 pistons and a comp cams 292magnum cam this has a .501 lift

sounds good right...rumpety cam.... thru this thing together and ran it....it ran 14's.... where did we go wrong....I already knew...

The stock head were a major hold back....changing the heads to sportsman II's neted over 100hp just the bolt on....the other place....well after the actual pour of the engine the "actual"compression was closer to 8.9:1 than the 9.5:1

The moral of this story is just because you get the same parts as some one describes does not mean you will make the same power...I knew the mistakes before I even assembled the engine and wanted to do an "off the self"rebuild after correcting everything the 350 made an honest 375hp and ran 12.00 flat...

just goes to show the DIY'r can get/make something that does not perform there are a lot of tip and tricks you need to know in a successful engine rebuild to make the power you want.... most time this will envolve "mocking" up the engine several times before the actual build begins....

The combo I suggested will run what I said it would...especially if you used the cam you mention...but you need to make sure of your exact tolerances....

If you are serious about this build I will help you in any way I can....also order a Lunati catalog...you will need the formulas in the back...plus some basic engine tool to do the math work....Terry

I appreciate all ur input on this build. just curious though, as i think it will be more cost effective for me to stick with a solid setup if i buy this short block.

i threw a xs274s 236/242 501 510 cam in the dd2k. it made a nice curve for what i need... i think. slightly lower tq/horse til 4k than ur combo, then opposite. could u do the same and see what u think of it?

it would do the same....as you up the duration of a cam you also up the power curve....as you do that in some cases you take away from the bottom end.... leaving a dog until you hit the band...that cam would work well in a 383 and would be less noticable than in a 350.....

For most daily drivers I try to stay conservative on the cam choice and build for more torque (hp will naturally follow)....

My last toy I build for a customer was a 86 Elcamino with a 400 @.030 with dished pistons (8.8:1) I used a Crane 216 dur@.050 .430 lift and decided to put all the effort in the heads...I used the stock open chambers and heavily reworked them..I used Manley Street Flow 2.02/1.6 valves and this netted me 445hp at4800-5000 rpm with and Edelbrock 2x4 lowrise intake with to Edelbrock 600cfm manual carbs....The cam was real conservative and all the power came from the heads...but theres more in it with better heads and maybe a bigger cam...

I also used a 700R4 tranny and the stock 3.42:1 rear end....

this car would not hook till 3rd gear.....45mph in second and punched it and it got real squirly....in 3rd if you punch it will burnem around 20-30 feet @ 50mph....1st gear is entirely useless...nomatter how you feather the throttle it won't stick...2nd gear takes a little work to go....fun to drive and could be a mid 11.50's car.....It's all in how you put it together....