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Just got a 350 crate GM10067353 was not looking for a motor but it found me. The heads on it are 1.940 int and 1.50 ext. and 76cc non vortex. I have a new set of World S/R Torquer 67S part# 042660B heads. Bigger valves and smaller combustion chamber. I may also be useing a Comp.cam simular to a Chev 327/350HP hydrolic.
Will it work or will I need premium Gas?
just need more info to give you advice; like all the engine specs ...............
Kitz
Thanks it is a 249HP crate, Touque 304@3500RPM,4bolt 2pc.main 4"bore,3.480strock,cast iron 76cc194-1.5 heads,cam is .390/.410lift.
Just want to know if changing the heads from 76cc to 67cc will work and what would the compression ratio be? It is 8.5:1 now. Also the valves are 2.02 and 1.6 in the smaller 67cc heads.....Thanks for your help....Jim
All else the same going from 76 to 67 8.5 to 9.3
9.3 looks about right to me too. I am assuming a 600 cfm 4-barrel carb and decent dual plane manifold and headers/mufflers. With the head change alone I would anticipate a 35-50 hp boost. The stock cam is pretty bad. Something in the .510 to .552 range would really help out.
May be able to run 89 octane, probably not 87, and of course once you give it some 93 you probably won't want anything else.
Good luck, Kitz
Thanks there in a web site for cal. www.csgnetwork.com and look for automotive. If I knew the piston dish or dome I could be rite on th P/N 12514101.
Al I did with web site is to play with piston untill the ansewer match 8.5:1 with 76cc and them changed to 67cc. 8.53:1=9.31
Depending on what head gasket is in there now if .028 I will go to .038. This drops it to just under 9.0:1. I think that will let me run 89 octane.
OK now I need to find how Compresion ratio's = what Octane you need?
Do some research on GM Performance Crate engines and I'll bet you can match one fairly closely to what you are going to do. The usually tell you what octane fuel to run with. Are your heads steel or aluminum? With alum I think 89 octane will be fine, perhaps also with steel.
Kitz
Those are steel heads. Max valve lift = 0.560. Probably need at least 89 octane at 9.0 to 1. Match a cam to the carb, intake and headers, and you should gain siginificant horsepower.
Thanks for all the help. I will finish the car it's going in and let you all know what happens.........Jim