Compression questions....???
Thread Starter
Junior Member
Joined: Feb 2008
Posts: 6
Likes: 0
Compression questions....???
Hi im 15 building my first sbc. im wondering if my thoughts about my set up are right. first off its a 350. what kind of compression am i looking at with 58cc heads, felpro head gaskets, stock deck hight, sealed power hypertonic flat top 4 valve reliefs and true 1.560 not 1.540 compression hight, stock rods and stock crank.
will there be and problems that will need to be adressed with this combo?
thank you for any help input or suggestions.
will there be and problems that will need to be adressed with this combo?
thank you for any help input or suggestions.
Supreme Member
Joined: May 2006
Posts: 1,857
Likes: 0
From: Maui, Hawaii
Car: 1984 Trans Am
Engine: broken 385sbc
Transmission: G-Force rebuilt T-5
Axle/Gears: Currie 9" Ford 4.30:1
Re: Compression questions....???
perfect age to start building.. i was 15 when i built my first.. well anyways, research more into the parts you want and heres a compression ratio calculator that you can use.. if you are going to use iron heads, stay UNDER 10.5:1.. for aluminum, stay under 11:1.. this is considering you only use 91/92/93 octane.. for 87 octane, minus a full point..
http://www.kb-silvolite.com/calc.php?action=comp
dont worry too much about the dynamic ratio unless you are reaching the limit on compression.. thats where cam duration comes into play.. any other ???'s, ask..
http://www.kb-silvolite.com/calc.php?action=comp
dont worry too much about the dynamic ratio unless you are reaching the limit on compression.. thats where cam duration comes into play.. any other ???'s, ask..
Thread Starter
Junior Member
Joined: Feb 2008
Posts: 6
Likes: 0
Re: Compression questions....???
also i want to use my original 76cc heads but i want to get around 9.5:1 compression out of the motor and i am wondering how i do that with those large chamber heads
Supreme Member
Joined: Apr 2004
Posts: 1,077
Likes: 0
From: Denver, CO
Car: cleanest '86 sport coupe around!!
Engine: 355ci twin 66mm turbos on e85
Transmission: built rmvb th400 w/ t-brake
Axle/Gears: 3.23
Re: Compression questions....???
dome pistons....but if you can score some 58 or 64cc heads relatively cheap, i'd go that route and then you can run plain 'ole flat top pistons and easily reach your compression goals
Supreme Member
Joined: Jul 2005
Posts: 1,675
Likes: 3
From: Arab, Alabama
Car: 1988 Trans Am GTA
Engine: 350 4BBL
Transmission: 700R4
Axle/Gears: 3.27
Re: Compression questions....???
Otherwise you would have to use a dome piston (everyone hates them but me) to get a decent C/R with the 76cc heads on a 350...
Supreme Member
Joined: Apr 2004
Posts: 1,077
Likes: 0
From: Denver, CO
Car: cleanest '86 sport coupe around!!
Engine: 355ci twin 66mm turbos on e85
Transmission: built rmvb th400 w/ t-brake
Axle/Gears: 3.23
Re: Compression questions....???
dome pistons usually don't have a large following because of the piston-valve clearance issues with them if you're not spot on in your measurements....ever had a piston smack a valve @ 6000rpms?
Supreme Member
Joined: Jul 2005
Posts: 1,675
Likes: 3
From: Arab, Alabama
Car: 1988 Trans Am GTA
Engine: 350 4BBL
Transmission: 700R4
Axle/Gears: 3.27
Re: Compression questions....???
Everyone I know says that they are "old-school" and worry about "flame propogation" across the combustion chamber thinking that a flat-top gives a much better "open" combustion chamber. But there is a whole lot more going on in the combustion process than meets the eye...
Look at motorcycle engines (or any high output-per-cc engine)
They ain't flat tops...
Trending Topics
Joined: Mar 2000
Posts: 43,187
Likes: 42
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
Supreme Member
Joined: Jul 2005
Posts: 1,675
Likes: 3
From: Arab, Alabama
Car: 1988 Trans Am GTA
Engine: 350 4BBL
Transmission: 700R4
Axle/Gears: 3.27
Re: Compression questions....???
Sofa commenting on 882 heads in this THREAD:
He was actually being kinda mellow about it
...
They will however, run slightly better than an engine without heads.
Not worth it. Wouldn't be worth it, even if they were FREE, and even if somebody else did all the work and paid all the misc expenses like gaskets and such to put them in your car. No matter what heads you have now, that casting is worse. Even if you have TBI swirlies. They're SURE not worth putting labor and machine work money into.
That's one of the worst, most anti-performance castings there is.
I've PAID people to come haul piles of that kind of crap off my property.
Catch me sometime when I'm not in such a good mood and I'll tell you what I REALLY think of them.
That's one of the worst, most anti-performance castings there is.
I've PAID people to come haul piles of that kind of crap off my property.
Catch me sometime when I'm not in such a good mood and I'll tell you what I REALLY think of them.
He was actually being kinda mellow about it ...They will however, run slightly better than an engine without heads.
Last edited by Supervisor42; Feb 23, 2008 at 11:58 AM.
Thread
Thread Starter
Forum
Replies
Last Post
WhteRbt
Tech / General Engine
2
Sep 21, 2015 09:48 AM
