Engine Build Question - Team Camaro Tech
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post #1 of 8 (permalink) Old Feb 7th, 07, 06:59 PM Thread Starter
 
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Engine Build Question

I am putting together a 383 and want to make sure I am not making any bad choices for the combo. The block is a two bolt main ----010 casting that has 010 and 020 cast in the timing chain area the block is a 1973 or 1974 vintage. This is just a low end engine for a street strip car. The block has been bored to 4.04", I plan on buying a scat or eagle cast crank internaly balanced, 5.7" scat rods, flat top hyper pistons . I need to deck the block to 0 deck. The manifold will be a cyclone dual plane, flow tech headers, looking at using a 750 quadrajet with a adapter plate but also have a 650 and 750 holley vac sec. The heads are gm casting 993s that will be mildly ported and completly rebuilt 1.94 1.5 valves 75cc, I am not planning on using screw in studs but possible pinning them if need be. The head gasket will be .030 thick. The cam choice is a comp cam http://www.compcams.com/Technical/Se...umber=12-246-3 . Melling oil pump stock pressure and volume. HEI dist. th 350 trans 2500 stall, 4.11 gear looking to put it in a third gen once I find one .
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post #2 of 8 (permalink) Old Feb 7th, 07, 08:24 PM
 
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Re: Engine Build Question

First off, check your piston, "down-in-the-hole" and if it is a stock, about .025" then leave it alone and just use .015", .017" or .020" thick shim headgaskets and save the machining cost..

And I would shoot for right at 9.75 to almost 10 to 1 CR. so I wouldn't have to worry about pump gas. That and a 268 to a 274 hy-cam and you will be good to go, imho...

A PN 3310-, 750 Holley on their old 300-36 true high-rise intake should be a dandy of a set-up for you as will be a set of 1.625" dia., 4-tube, long headers and a free-flowing exhaust..

Nothing fancy at all.

pdq67



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post #3 of 8 (permalink) Old Feb 7th, 07, 09:04 PM Thread Starter
 
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Re: Engine Build Question

Ill be at about 9.8:1 depending on the true head cc and the piston valve relief with the .017 shim and I have a 270 magnum cam and some crane anti pump lifters. I was just going to use a polished 350 crank I have but the dynamic compression was around 7.4 which seemed kind of low. Thank you for the suggestions.
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post #4 of 8 (permalink) Old Feb 7th, 07, 09:32 PM Thread Starter
 
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Re: Engine Build Question

On the lines of my previous post the reason I really went to the 3.75 crank was to raise the compression slightly and avoid the use of domed pistons. Should I decide to use the 350 crank and pistons with a small dome what problems would that create? Would is still hurt the flame travel in a open chamber head?
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post #5 of 8 (permalink) Old Feb 7th, 07, 09:56 PM
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Jim
 
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Re: Engine Build Question

very similar to the motor I run, I stroked my 327 to 383 last year, same comp, same cam, I got better heads. (I was budget limited to bottom end only, cam, heads, and bigger carb are on a future shopping list.)

My power and rpm are limited by the cam and heads. She gives me 400 RWT @ 4200 & 293 RWHP @ 5200. On the other hand, I have 350 RWT @ 2000, which makes her a blast to drive around...

What will you have to give up for better heads?

The 383 you planned is a perfect midrange torque combo, and I know from experience it will work well. It won't be a "buzzer" tho.

If you stay with the 350 crank, and if I'm remmebering right that a small dome ("11:1 style") is positive 6.5 cc's, then your comp will jump to 10.5:1 @ .040 piston to head clearance. Bump that to 055" (undecked block & 030" gasket or some such combo) and your comp will drop enough to be pump gas premium friendly.

If you buy better heads w/70cc chambers, the 350 will work with flat tops, deck and gasket for .030 quench, you end up at 9.8:1 static, 8.06:1 dynamic. This 350 would rev better than the 383, and would be a pretty sweet motor, IMHO.





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post #6 of 8 (permalink) Old Feb 8th, 07, 05:49 AM
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Gary
 
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Re: Engine Build Question

Jim, I have to disagree on the gasket thing. It's been proven more than once that a quench wider than about .045 or so will have a tendency to detonate more than one with higher compression and tighter quench. My machinist built a replacement for his truck with .025 quench, 10.4 compression and junk TBI heads and he can fill up with pi$$ and not ping.

Gary Adrian
FCS Harmony Racing

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post #7 of 8 (permalink) Old Feb 8th, 07, 06:18 AM
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Jim
 
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Re: Engine Build Question

Definitely debatable, Gary, and I'd usually agree with you. In this case, if my numbers were right, I came up with 10.8:1 static on the 350 w/domed pistons, and DCR way too high for pump gas with that cam. Now if he had a 280 cam... I figured on 1/8" dome minus valve reliefs at pos 6.5cc, my memory could be faulty here, the numbers do seem high.

Frankly, assuming some of the parts he has must be used due to budget, and he has a good 350 lower end, I'd keep it a 350 and spend what money I had on decent heads, and build scenario 3.





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post #8 of 8 (permalink) Old Feb 8th, 07, 08:01 PM Thread Starter
 
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Re: Engine Build Question

I have to agree the heads are not the best choice but the cheapest I can find something else is $700 which is more than I want to spend on this 2 bolt main engine so unless something else comes up Ill try my hand at porting these and see what we end up with. I was thinking this over a bit and ran some more numbers with the 350 and I think it may work. The comp cam http://www.compcams.com/Technical/Se...umber=12-246-3 seems to produce more power(according to dd dyno) than the 270 magnum, so I ran the numbers with it. I found that Keith Black has a set of dome pistons .100" that displace .5cc of cylinder volume(KB105) if I use these with a .017 thick head gasket and a stock deck height of .025" gives me a quench height of .042" with the piston compression height of 1.561. The rods I think I am going to use are 5.7" because that is what the pistons are set for using that rod length my dynamic compression is 7.92 and my static is 9.77, cylinder pressure max is 185.5 @4000 rpm and the ve is 92.5% at 4500rpm with a 750 cfm carb and a high flow dual plane manifold. I used some flow numbers from the 882 head cause I could not find the 993 # but I think they will be close. Hopefully I crunched the numbers right cause I got a headache lol. What do you guys think? It spit out 413hp @5500 rpm and carried it to 6000, The torqe was 440 max at 4000 rpm.
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