High compression!!!

[Bradley Palmer]

Im sending my heads of in a few weeks to get them ported and polished and a five angle valve job done. My question is should i get .550 double springs installed with 1.9 rockers?? The cam im getting to go with this package is going to have a pretty high lift on it so thats why I am doing this. And also will milling the heads take the compression up much higher or will getting JE to make me a custom set of high comp pistons be a better deal??

[pgriffith]

Milling the heads will raise compression but you can only mill so much. If you want really high compression probly gonna be better to find another way. Like pistons. I milled my heads 20 thousands and it gained about .4 compression.

[Bradley Palmer]

How many hp did that give you??? And if i get high com pistons will that cause valve to piston slap?? I will be running .550 springs and 1.9 rockers with a high lift cam..

[navyblue2000]

piston slap comes from over bore in the cylinder, rosy palmer...eek, bradley palmer. i think you would know this by now.
why port heads, when you can get a dual shot of the naws? :rolleyes:

[Bradley Palmer]

Piston slap is when a valve hits the piston right?? Anyways im still going to put (nawwwwss) on my car im doing the p&p and nitrous.

[Patrick Javert]

3800performance.com is working on .02 overbore pistons as we speak w/ compression ratio's of 9.5:1 and 8.5:1. high lift cam+1.9 rockers=bad. tell thee company that is making your cam about the 1.9 ratio rockers you plan on running and have them make the cam w/ that in mind. BTW, head/cam are much better in the long run than nitrous for the simple fact that you don't have to refill any bottles, and it's always providing hp/tq.

Don't mill the heads bc there will be piston slapping occuring if you do.

[ May 27, 2002: Message edited by: Patrick Javert ]</p>

[strange_trp]

<blockquote>quote:</font><hr>Originally posted by Bradley Palmer:
Piston slap is when a valve hits the piston right?? <hr></blockquote>

the term piston slap is generally referred to when the clearance between the piston and the upper portion of the cylinder wall has become excessive.
i think you're talking about piston/valve interference.

[phoenix64]

piston slap is when the piston is lose in the bore, and is striking the cilinder wall, its either a bad fit, or a busted piston skirt. This is a common cold start problem, with chevys, but goes away when the engine warms up. it has nothing to do with the head.

[bluecmaro96]

patrick why do you post your opinions as factual info? Magnus and i both have the heads milled .020 and he doesnt have piston slap.

[DominusEtDeusNatus]

I'm going to assume that your high lift cam has lift over .500. So let's just use .500 with 1.9RR. That's .594 lift!!! That's very high. I hope you know what you're doing.

[Patrick Javert]

right, but he's also looking into increasing lift as well. a few tousnadth's here and there add up. I wouldn't be worried about piston/valve clearance until higher rpm's anyway, since that's when there's the most chance for valve float. also, the new pistons that 3800performance is making is 9.5:1 and 8.0:1, not 8.5:1. sorry about that. also, Bluecmro96, do you have the specs on where the piston sits at TDC, whether it's still in the cylinder, at zero deck, or out of the cylinder at all? I haven't been able to find the specs anywhere.

[P-nut-]

I have posted some useful tech documents that could probably help you. You can find the here:
http://www.ditechllc.com/mitchell/2000/

The document that would probably help you is 3.8l.v6.pdf it has the engine specs.