FrontEngineDragsters.Org Forum
Technical => Matt Shaff's Engine Shop => Topic started by: Brian on February 07, 2013, 08:33:29 AM
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Hi Matt. I am brining this from the FED room. It was suggested that I ask you.
I have been beating my brains out trying to get 13:1+ out of this motor with the 64cc heads. I can get 12:1 pretty easily. Do you think there will be a noticable difference using 12:1 vs. 13:1? My goal is 500+ HP here is the rest of my set up.
302DZ Block +.030 (306ci)
2.02/1.60 iron fulie heads 64cc, ported
1178 forged crank turned 10/10
K1 H Beam rods.
Piston - whatever it takes to get the compression i need.
Cam - Undecided
Hilborn Mech Inj with 12" stacks
I really appreciate any feedback. THank you.
Brian
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Brian:
To get 13 to 1 compression from your 302 is tough.
With 64cc heads and a typical .040" gasket and the piston .010 in the hole, your going to need about 23cc of piston dome.
I looked and did not see anything thats a "shelf" piston. Custom pistons are the only way to get that much dome.
You don't have much swept volume with the small stroke.
You stated that 12 to 1 might also work. About 18cc dome will get you 12 to 1.
I don't think you will see much power difference between 12 and 13 compression.
You have to get so much dome volume that it hurts the air flow from the intake ports and flame travel also suffers.
What you gain in compression you loose in efficiency. >:(
Way back when, [showing my age] we used to angle mill those heads down to about 57-58cc chambers.
Then you can use a "shelf" piston and get more compression.
BUT [here it comes] you will find it way more user friendly to put a bigger stroke crank in it.
If your using this engine for sentimental reasons I understand.
Keep the block but put a 3.25 or a 3.48" stroke crank in it and have a better selection of parts.
You can still use the same rods and get 327 pistons or 350 pistons. Smaller dome, less cost and more power.
If your like most of us you can only afford to build one engine.
Thats my 2cents and thats all its worth! ::)
Matt
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Matt
Thank you for your responce. Its the best advice I have had. I am not opposed to putting a stroked crank in it. Just to confirm, with a 3.25 or 3.48 crank I could still use my 5.7" rods with 350 piston? Would I still be able to use the 64cc heads or should I try to mill them down to get closer to 58cc's?
Thanks again for your time, I really appreciate it.
Brian
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Brian:
I am assuming its a large journal motor: 1968-up.
The 5.7 rod was used in all the small blocks with the exception of the 400.
1967 and older used a small journal crankshaft - rods and mains and 68-up is large journal.
If you have a small journal then the 327 crank [small jr.] is as big as you can go.
If you have a large journal then you can use the large journal 327 [3.25" stroke] or the 350 crank [3.48" stroke].
A DZ block is 1969 I think. Large journal. and so are your rods.
Matt
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If you have a dz block IMO you would be better off selling it to camaro guy.You can get pretty penny for it.Then you could buy better block and be money a head. The 302 was only built so z/28s could run in trans am racing which at the time had 305 ci limit. Its not bad motor but it loves rpm. A 350 would be stronger and you can get better parts cheap since its so common. JMO
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Brian i come from a circle track background which had a cid limit and a flattop piston rule . flycut my heads to 47cc combustion chambers and had the block zero decked and we got monster compression . Thin composite head gaskets. What type pf heads are you using.
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We improved our 355 cid SBC last year from 11.6:1 to 13.4:1 . With a new custom cam , some intake port work and a complete race rebuild gained 40 hp.
We haven't seen a great deal of on track improvement yet. We ran a 5.10 et @ 136 Friday.
My advice is to build a 400+ cid engine. You don't have to get wild to make 600 hp on injected alky.