Thread: 355 build HP and Torque?

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Update:

After cleaning off all the carbon deposits, of which there was hardly any, and with the valves still held in by the original springs, I cc'd the Vortec heads tonight.
6 chambers measured 66cc's
2 chambers measured 65cc's.
I didn't have the correct sparkplugs, so I used the old set out of the 89 350. They are shorter and hang back in the threads. The sparkplug hole inside the chamber held about 1/2 cc to fill it up flush with the chamber, so deducting the 1/2cc from the above measurements would give 64-1/2 and 65-1/2.
So now what do I do to balance them if needed?, or is that close enough?
Do I match the larger ones and remove 1cc material from the 2 smaller chambers? I read about "sinking a valve" on another racing site. Should I have my machinest grind the exhaust seats a little on those 2 chambers to make them even?

Actually I'm wondering if my measurements could have been off just enough, to not worry about it and assume they are all pretty close as they stand.

At this point I am assuming the heads don't need a valve job, although I do plan to do a simple fine lap job on the seats, after they check out on the magnaflux and then pin the studs and install the beehive springs.

Using 65.5cc and 18cc dish pistons, and a .040 quench, I calculate an 8.90 SCR and 8.08 DCR with my new cam calc of 29 IVC at 0.050.

Wow!, Look at all those numbers I'm throwing around, that I had no clue about a few months ago.

I think my next step is to finish stripping the block, taking it to the machinest, verify the bore size and order the pistons.

Thanks again for all your input.
Together we are going to build a very nice engine.

Originally Posted by rollie715

So now what do I do to balance them if needed?, or is that close enough?
Do I match the larger ones and remove 1cc material from the 2 smaller chambers? I read about "sinking a valve" on another racing site. Should I have my machinest grind the exhaust seats a little on those 2 chambers to make them even? Actually I'm wondering if my measurements could have been off just enough, to not worry about it and assume they are all pretty close as they stand.

For a street driver motor, I wouldn't worry about the 1cc difference. The only reason I'm expanding on this is because of your eagerness to learn.

What I would do is to sit the heads on a flat and level surface with the chambers down and stand up the edge of a straightedge on the top of the valve stems to make sure that none of the valves are installed shorter or taller than the other ones. If the valves are reasonably the same height from the deck, then measure from the bottom of the straightedge to the surface where the heads are sitting to see if they run downhill or uphill from one end of the head to the other. This will require that you use a buddy to hold the straightedge while you place a standard under the straightedge at each end of the head, right up against the head and measure the difference between the top of your standard and the bottom of the straightedge with feeler gauges. I'm trying to explain this so that most anyone reading it can do it without the use of precision tools which they may not have. The standard can be anything that is flat on the bottom and offers an area on the top where you can insert a gauge blade between the standard and the bottom of the straightedge. When I was a young man with few tools, I used an upside-down drinking glass from the kitchen. Use the same glass on each end of the rule of course and measure at the same place on the glass bottom. You might mark a spot where you will measure with a Magic Marker or Sharpie. Of course, to do this properly, you should measure all valve lengths with a 6" dial caliper or other suitable tool. If you don't have one and can't buy one, have a buddy measure them or go down to the machine shop and pay 'em their shop fee to measure them for you. You will want to measure the margins also and see that you have a matched set of valves. As good as it could get is that the two small chambers could have the valves closer to the deck than the other valves in the other chambers. Then you could cut the seats a little to equalize the distance from the deck to the seats on all valves. Then you'd equalize valve stem heights and you'd have a set of blueprinted heads.

I've read that the L31 design was reached only after GM engineers tweaked for six months on their best Corvette LT1 chamber design. THEREFORE; RESIST ANY NOTION YOU MAY DEVELOP THAT INVOLVES GRINDING IN THE CHAMBERS BY YOU OR ANYONE WHO DOES NOT HAVE A DOCTORATE IN FLUID DYNAMICS.

Originally Posted by rollie715

At this point I am assuming the heads don't need a valve job, although I do plan to do a simple fine lap job on the seats, after they check out on the magnaflux and then pin the studs and install the beehive springs.

Check carefully what the angles and the dimensions are on the seats and valves. I've read from more than one source that the valve job from the Chevrolet assembly line is about as good as it gets and contributes greatly to the flow of the heads, so, you don't want to fix it if it ain't broke. If they held the fluid for you to do the cc procedure and didn't leak into the port, then leave 'em alone, assuming they're low-mileage heads. Number the valve faces upon removal so you can keep everything in order upon reassembly.

Originally Posted by rollie715

Using 65.5cc and 18cc dish pistons, and a .040 quench, I calculate an 8.90 SCR and 8.08 DCR with my new cam calc of 29 IVC at 0.050.

Wow!, Look at all those numbers I'm throwing around, that I had no clue about a few months ago.

LOL, funny stuff. Reminds me again that I should have been a teacher. Not all is lost though, I'm able to contribute in my own way.

Originally Posted by rollie715

I think my next step is to finish stripping the block, taking it to the machinest, verify the bore size and order the pistons.

Sounds ok to me.
In my opinion, you'll be better off in the long run if you can save the cam bearings by not using a caustic cleaner on the block. The shop will want to replace them because that's how they make their money. You, on the other hand, should be making your decisions by what you can afford to do that will still offer a good service life. I got tired of all that expense of changing cam bearings on street motors and the fact that usually, the replacements were slightly small or slightly large or slightly narrow or whatever. The ones that the factory put in will work fine for a long time and I would only replace them if there was excessive play between the cam journals and the bearings. There are more than likely fellows on here and other places who will tell you to change the cam bearings every time. If they make more sense to you, then follow their advice. I just know what works for cheap for me.

Thanks for the advice on the valves. Just for fun I may put a straight edge accross the valve stems and see how even they are, but if 1cc difference accross the chambers is acceptable, I probably won't spend too much more time on this set.

I appreciate your willingness to fill in extra details, as I am interested in finding out more of what it would take to create a finely tuned or blueprinted engine. Maybe someday on a future build, I will spend more time buiding one with more precision. I've still got a ways to go on this build and haven't even got to the transmission, headers exhaust system, or rear end. Or for that matter, my entire 67 Camaro has a lot of tweaking needed throughout. Just yesterday, when my wife went to fasten her seatbelt, the belt pulled out completely where the original belting stitches failed. Now I'm looking for a new original replacement in blue. I digress. My vision at this time is to badge the car as an SS350 and paint and accessorize this new engine to appear as close to original as possible.

Originally Posted by techinspector1

In my opinion, you'll be better off in the long run if you can save the cam bearings .....usually, the replacements were slightly small or slightly large or slightly narrow or whatever.

I have already removed the original cam bearings. I bought an sbc cam bearing tool and did it myself after my machinest advised me to do it before I brought the block in to be hot tanked.

On the subject of replacement cam bearings, can you recommend a brand or part number that would be of good quality that could avoid getting out of spec bearings as you suggest happens sometimes?

As for the crank bearings, the 350 crank kit I purchased per your suggestion from Mabbco in Texas came with a set of bearings, looks like 10/10, the rod bearings are Clevite made in USA, the mains are EngineTech made in Israel. If I check the endplay with a feeler gauge and the clearances with Plastigage, I assume they will work just fine. I didn't realize bearings were made out of aluminum.

Originally Posted by rollie715

On the subject of replacement cam bearings, can you recommend a brand or part number that would be of good quality that could avoid getting out of spec bearings as you suggest happens sometimes?

Let your machine shop guy supply the bearings, he knows what is currently the best choice to use.

Ok, I'm ready for my next lesson.

I've been thinking about valve rocker geometry and push rod lengths.
I was under the impression that the rocker pivot point was located a little lower then the endpoint contact points of the valve stem, so that as the valve approaches it's maximum openings and when the pressure against the valve stem is at it's greatest, the pivot angle in relation to the valve stem is crosses over the 90 degree point, which would result in the least amount of sideways travel and the least amount of side pressure on the stem as well as the least amount of sideways rubbing between the contact surfaces,

I would like to make a scale cad drawing of these relationships so I can better understand the variables and more easily communicate these principles to others. And to apply it directly to my project and cam lift.

Where can I go to find the exact geometry and dimensions of my setup? GM 906 Vortec with stock rockers.

And please feel free to present a detailed discussion on this subject, and to fill me in on what I don't know yet.

Thank you.

Originally Posted by techinspector1

Let your machine shop guy supply the bearings, he knows what is currently the best choice to use.

I dropped the block and heads off at the machine shop today.

Shop guy recommended Durabond brand cam bearings. I ordered the high performance style with the Teflon coated surfaces. Supposed to hold up to higher pressures and temperatures if needed.

Work requested was:

Hot tank block and heads
Magnaflux heads
Measure bore size and I will provide pistons accordingly
Bore cylinders using torque plate
Surface deck according to my stacked component measurements to achieve 0.040 quench, and be parallel with crank.
Install pistons on rods
Balance complete rotating assembly

With his existing schedule, this may take 2-3 weeks to complete.

It was nice to talk to a real person about the details of this project.
We hit it off very well.