5.7 cylinder head recommendation

[aldfaa]

Going to rebuild a 5.7 as a winter project. Several weeks ago I lost the motor from a dropped exhaust seat due to a cracked exhaust manifold.

The motor is a 1996 5.7 crate that was using the 1986+ style 64cc non-vortec heads and mechanical flat tappet cam. Last year it was upgraded to a 4 bbl but it was cobbled due to an early style intake with the wrong center bolt angle being used.

I don't want much more power due to outdrive limitations, just looking for around 300h.p. Should I stick with the 86+ non vortec heads, Go vortec ( and get correct intake for quadrajet), or go for some aftermarket heads?

Looking at doing a .030 overbore, flat top, four valve relief pistons, and a comp cams X270 marine cam. Or do you think this is too much?

 

[aldfaa]

Re: 5.7 cylinder head recommendation

Sorry,wrong section. Mods can this be moved to the mercruiser section? Thanks!

 

[Alpheus]

Re: 5.7 cylinder head recommendation

Vortec heads are the easiest and most cost effective 25-30 HP gain money can buy. Just make sure if you buy used ones to have them inspected at a machine shop before just bolting them on...

 

[John_S]

Re: 5.7 cylinder head recommendation

Don't go to flat tops with the 64cc heads. Stay with the recessed pistons like the stock marine engines. Flat-tops will give you a 10:1 compression ratio. You want to be in the lower 9's. The over-bore will raise the ratio slightly, as well.

Another vote for vortec heads. Stock heads should be fine, but beehive or other springs might be needed depending on cam choice. Screw in rocker studs wouldn't hurt.

Edelbrock has a performer intake that will take a spreadbore or squarebore carb. It is a mid-rise dual plane intake. You will need to find a marinized one if you are raw water cooled and boat in salt.

Cam might be a little too much. Just stay with something that is slightly over stock specs, and lift that doesn't exceed vortec heads.

 

[chaparall villain 2]

Re: 5.7 cylinder head recommendation

i have vortec heads on mine and i like them but you have to have vortec intake .. and like the people stated they have the small combustion chambers so have the machine shop figure out what you need for pistons cc wise in dish to keep compression down .. on my cam i didnt buy a marine cam and lifters but i looked at the specs for marine and found a truck cam that was real close to the specs and cheaper by far ... on the intake i would get one for idle to 6500 rpms and not the one for 1500 up ... i had one of those on mine and it was doggish out of the hole so i replaced it and now it does great and if you go over 500 lift on the cam you will have to have different springs for the valves and some machine work done to the heads as a damper or double coil spring will bind on the pockets ... i learned that the hard way when i broke 2 springs in a weekend and had to be towed .... good luck

 

[chaparall villain 2]

Re: 5.7 cylinder head recommendation

if i remember monday i will try to get the specs on my cam i put in ... it does a great job all around and i have run it up to 5400 rpms ...

 

[franktrav]

Re: 5.7 cylinder head recommendation

patriot performance makes vortec heads for small block chevy.they will accept the standard 12 bolt intake,or the 8 bolt vortec intake. they also accept center bolt ,and perimeter bolt valve covers. the valvetrain is also set up to accomodate up to a .575 lift cam.assembled heads also have 3/8 screw in studs.http://www.jegs.com/i/Patriot+Performance/723/2151/10002/-1

 

[Aloysius]

Re: 5.7 cylinder head recommendation

Vortec heads and "d" shaped pistons are the way to go. It's all about "quench"..the squeezing of the charge to create turbulence, and mixing. This promotes rapid burn and more power, without having to have excessive timing lead to thoroughly burn the mixture. Fully dished pistons don't provide this quench feature.

don't "overcam" the engine..truck or marine cams are more than adequate.