I will be building my motor with forged componants...should i raise my compression with high comp pistons, or should i do it with a set of 5.3 heads? or a combination of both? I want as much compression as i can get while still running 92 octane pump gas.

 

milled 5.3 heads will put you there easy but it all depends on what cam you're getting

 

I would do it with a set of PP stage 3 LQ9 heads in the chamber size that will give you the ratio you want. They have several to choose from. This way you will have more piston to valve clearance because the deck stays pretty much stock except for a clean up pass.

Best part is that you can get any stage of this head for 1195

 

What compression are you shooting for? Iwould do it with both, but with as little milling as possible.

 

I went with angle-milled heads...58cc chambers, stock pistons, tight quench, thermal coating, colder plugs...

Since you're building from the ground up I might do a bit of both although I think I would get pistons with a relief cut in them.

Definitely go with coating to help avoid detonation...on the pistons, chambers, and valves...exhaust runners won't hurt either.

Just my $.02

 

what kind of coating should i get? how much does tht cost? and what brand of pistons do you guys recomend? what are few good sites to get them from?! thanks for the info guys

 

Domed and dished pistons affect the burn pattern, so you want as close to a flat top piston as you can get on 92 octane. If you had C16, it wouldn't matter.

Diamond makes a flat top with 2cc valve reliefs, which will help keep compression up and allow for a bigger cam. Mill the heads only as much as is recommeneded to keep flow up, but with the valve reliefs, you won't have to worry about ptv clearance.

LS6 heads, milled .030" give you a 59cc, and 5.3L give you 57cc. AFR 205s can be milled down to 59cc without adverse effects. Assuming Cometic .040" gaskets (tight quench cuts down on detonation), and pistons out of the hole .005" with 2cc reliefs in a 347, I get 59cc = 11.47:1 and 57cc = 11.79:1. Depending on the cam, you can run either compression on 92, though I'd be leary of the 11.79:1 in warm weather.

 

PrecisionPorting did my heads and coating...great shop to deal with.

Check out website (url above) for pricing or just call, Bob is very knowledgeable and can advise on what's best.

 

I would try and keep interference in the flame travel pattern to a minimum. You see, when the fuel ignites it makes for a more effecient burn when there is no obstruction such as a dome (Whether large or small) to get in the way. Then the combustion process has nothing to travel around to burn completely. I would use a small chamber head and possibly a coated piston (I hear good things about Mahle.). Make sure that you have good quench as well. Depending on your camshaft you may or may not need to pull a little timing out as well as there is a difference between dynamic and static compression. Good luck with your combo.

Jim C.

 

Def. keep quench tight...my research of it has taught me not to go above .040" (personally, I opted for .035" quench)

 

cool thanks for the info guys...i will look into that stuff.... any other opinions guys?!

 

Basically bottom line, do it with both, and keep milling of the heads to a minimum. It's a fine line i finding a higher comp piston with as flat a surface as possible while finding a smaller chambered head without milling. Keep searching/calling around. You'll figure out a good combo.