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I have a 90 350 shortblock that is a rebuild from Advance Auto Parts. It has inverted dome -23cc pistons. The heads that are on it are a set of 76cc heads from a 73 truck motor. I'm running stock felpro head gaskets. I was wondering if I should get some heads with smaller combustion chambers. I was thinking of running some 305 heads because I really don't turn the motor over 5000 rpm. I heard these heads are 58cc but they don't really flow very well over 5000. What are your thoughts?
.....Hi Gerald, I went to campbellenterprises.com & used there compression ratio calculator. With the -23 inverted dome pistons, .040 gasget, .0001 deck height & 76 cc heads your compression ratio is 7:68 to 1..... & With the 58 cc heads your compression ratio is 9:00 to 1..... Not sure of advatages/disadvatages on 305 heads on your application so others will have to answer..... zzzQuote:
Originally Posted by Gerald Streeks
Not even 8-1 compression sounds like garbage to me. I just know that this 350 should have more power and I think the pistons are killing the compression.
why not a set of 58cc 350 heads?
Trying to look for an inexpensive set of rebuilt heads and I don't think 58cc 350 heads are inexpensive.
Why not keep the heads you have got and put in a set of flat top pistons, this will set your compression up as well as increase combustion efficiency by improving squish and cutting down on turbulence. :)
Because the motor is already in the truck and I don't have the resources to pull it out but I do have the resources to change the heads.
Are your current heads good ? They have to be worth some thing ? 305 heads would work and smoke the tires with the right cam ,the upper rpm hp will suffer the most.
The current heads were just redone with z28 springs new valve guides and seals. I just think that the 76-78cc open chamber head is killing my compression. And I don't need upper rpm I don't turn the motor over 5500 rpm. The motor is in a 73 3/4 ton truck with 31 10.50's on it.
It has a lunati voodoo cam in it: intake at .050" lift 213/219 exhaust, 256/262 advertised, .454/.468" lift, 112 LSA 1000-5500 rpm.
A professional products crosswind intake similar to edelbrock air-gap, a 600 edelbrock carb, and headers.
You did'nt say what gear you have.Quote:
Originally Posted by Gerald Streeks
Also you did'nt say if you had a looser stall in it.
I.M.O.,I would look at a 1,800-2,000 stall.
With that tall a tire I would put more gear in it.
Those are big tires to try and move.
I've learned the hard way, you don't want high compression in a truck engine. Stay around 9.0 or less. A light car never has to pull long, the speed increases and the engine revs up. A truck will soon overheat the chambers and start detonation, forcing a downshift.
By similar do you mean "Chinese rip-off"???Quote:
Originally Posted by Gerald Streeks
If you want hot-rodding to have a future, buy from American companies that actually do "research and development" not "receive and duplicate"...
Buy the Edelbrock.
Last I knew Edelbrock did not have a copyright on their intake manifolds.Quote:
Originally Posted by allengator
How is it a rip off?
I would suggest you look at either the GM Fastburn aluminum head #PN12464298 which has 62cc chambers or the Edelbrock Performer Center Bolt head which has 60cc chambers. Either of these are a good buy and should raise your compression. You could also look for a used set of LT-1 aluminum heads which have 58cc chambers if you can get them resonably. Stay away from 305 heads--they don't breathe well enough for a 350 and the cam you have.
Professional Products is a company based out of California.
If it came from China you should tell those people in California to stop selling them. And hotrodding would have a better future if everything wasn't so d%mn expensive.
Where do you think Eagle,and Scat cranks and rods come from???Quote:
Originally Posted by Gerald Streeks
which is why they suck. <let the sarcasm flow> ive seen some of these chinese goods up close and personal and they really are some pretty shi&*y castings. have not seen that particular intake but have seen others with alot of cleaning up to be done to even come close to a edelbrock and besides rpm air gaps are only like 205 in jegs sometimes u can snag them for 199. thats not that bad.
Lets not minimize the quality of SCAT and Eagle products. They are quality castings, and their rotating assemblies are in use in many, many engines including mine. If they were crap, no one would use them.
I can tell you one year ago the 5th fastest IMCA modified in the country had that China made stuff in the bottom end.Quote:
Originally Posted by rumrumm
On the China made stuff we turn night after night at 7,800+rpm's with 13.5 to 1 comp. ratio.
In a 496 BBC I have sprayed a 300 shot of n20 on top of the 600+ hp the engine already has.
To buy the same crank in a 4340 steel made in the US I would spend more than double the money.