Thread: 350 build up help

Tweet

Hey fellas should I invest my money in my stock heads to port them out to 190 cc intake runners and shave them down to 64 chambers or should I buy new heads? The thing is though is that I want this to be a Edelbrock Performer RPM chevy and Edelbrock does not make one as I want, I could buy one of those but then Id be putting money in them to port them out.

Originally Posted by #1firebird

Hey fellas should I invest my money in my stock heads to port them out to 190 cc intake runners and shave them down to 64 chambers or should I buy new heads? The thing is though is that I want this to be a Edelbrock Performer RPM chevy and Edelbrock does not make one as I want, I could buy one of those but then Id be putting money in them to port them out.

Why do you think you need a cylinder head that has a port volume of 190 cc?

Firebird, check out this site for a review of how SBC heads flow. When you say you might port your stock heads to 190 cc for better flow you need to tell us the head numbers that are down in between the rockers and springs near the center of the head. If the last three numbers are 883 then you have the "best of the worst" stock heads. The old 327 double-hump 461 heads had much better flow but may not have bolt hole bosses in the end for accessories. If you have the 883 heads, they probably have thin walls and cannot be enlarged much. You would be better off taking a look at stock Vortec heads or one of several aftermarket heads. The AFR heads are very good but expensive. If you are going to run a compression ratio over 10:1 as you said previously the only way you might ( ? ) beat the need for high octane gas would be to get aluminum heads like the ones on a late model Corvette. In my experience you can safely smooth out the 883 exhaust ports but the intake walls are thin and they are not going to get you much over 300 HP. I already sent you a link to Ryan's Dyno tests and in there around example 45 or so there is a dyno run for a totally modified set of GM 883 heads which does not come up to aftermarket HP numbers for other heads.

Check out: http://www.chevyhiperformance.com/te...ench_database/

I am using 883 heads with just exhaust ports smoothed and leaving the tiny 155 cc intakes alone with rough walls to maintain fuel-air mixing and good low rpm torque along with slightly better mpg. If you want HP in the 400+ Range you will have to go to higher volume intake ports but for the street maybe 190 ccs is too large and folks on this Forum tend to favor 170-180 cc port volume for an engine which is run on the street. If I were doing it over again I would buy the stock late model Vortec heads for about $600 a set. I spent $300 on rebuilding the 883 heads and another $200 to smooth the exhaust ports so for another $100 I could have had the Vortec heads. You will notice that most of the 383 crate motors have Vortec heads because they are the best breathing stock heads. Read through the flow tests in the site I give above and you will see that there is a tradeoff in that large port volume is needed for high HP as you say, but then you may get bad bog at low rpm when you need to keep the ports small enough to get good flow velocity to pack the combustion chambers and smaller port volumes will do that, so maybe 190 cc ports are too large? You need to study up more and or find a shop guy you think you can trust and let him build the engine. Remember the Farmer who said to his wife, "Martha, I don't trust anybody but me and thee, and I'm not so sure about thee either!"

Don Shillady
Retired Scientist/teen rodder