SSP_6.2

While I have the heads off, would I be able to take advantage of compression bump even with my vvt cam? How thin could I go? I'm thinking about .030. Cam specs are 214/228 .559/.571 on 114lsa

DavidBoren

I think there's more to this equation than just compression. With the vvt cam phasing, ptv clearance needs to be a measured at both extremes of the phaser limits. And you want optimum quench, more than just blindly increasing compression.

redtan

iTrader: (5)

That's pushing it in the quench department. Ideal is around 0.040 give or take a few thou. So even withouth the issue of any PTV you're going too far.

You can also mill your heads while they are off.

showdog75

iTrader: (8)

I've got to pull the heads of my ls2 that's sitting on a engine stand. I was spraying some stability fogging oil in the cylinders and the red straw shot down #3 cylinder. I think stock gaskets are .052 but I noticed that Cometic offers .040 and .045. I understand quench from hot rodding Harleys and optimizing it made for a clean efficient combustion cycle. Would going with a .040 gasket cause any issues with the pushrods and lifter travel? I could be wrong but I doubt. 012 will cause piston to valve clearance issues with a basically stock engine. I'm not talking about a VVT engine as mine is a ls2. Any input? Thanks

DavidBoren

If you are removing the heads anyways, you should measure how much the pistons are above the deck, and order the correct thickness of gasket to achieve the desired squish.

Especially if the heads are already coming off. You have the opportunity to gather true empirical data for your engine, why not just do it right and actually measure how much the pistons stick out of the hole?

showdog75

iTrader: (8)

I concur totally. On Harleys I'd use soft solder and turn the engine over slowly then measure the solder. Works well. I've yet to have a ls engine apart so pardon my ignorance but are the pistons typically proud of the deck?

DavidBoren

It's pretty common for the pistons to be .007" out of the hole, yes.

KW Baraka

iTrader: (7)

Exactly!^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Optimal and safe quench in a street engine is about .035" to .040" Getting to this point is WAY more important than any attempt to hike the compression ratio....but if you do hike the compression ratio, it's absolutely essential that you get to this point! Street/strip racers who take their engines apart fairly often will go to .030" quench....but they run 12+:1 compression.

With a stock engine that meant for regular and lasting street duty, you want a .040" compressed head gasket (about .034" quench).

Going any thinner is just silly from a potential cost versus potential benefit standpoint.

KW