If I mill my stock 243 heads 0.030" and put them on my stock LS2 short block with stock GM head gaskets what will the compression ratio be?

Stock CR is 10.9 to 1.

For not so simple version of same question, CLICK HERE.

 

What about looking into porting the heads instead of milling them, and then if you still want, maybe mill them and use a thinner MLS gasket to get the CR where you want it. Milling .030 off may require you to mill the intake as well. I had to do that with .030 milled off my LT1

 

ttt for Monday Morning

 

I was told, when I was working on the same decision, that a thinner gasket like the .040 will raise compression to 11.44 and is a better move than milling the head. Milling the head changes the combustion chamber shape, and it's designed like it is for a reason. Also, the thin gasket reduces the risk of detonation vs. milling and a thin gasket.

I don't remember exactly why now........but I did it and I love the results.

 

Thanx, Joe, that is exactly the kind of information I am looking for, from someone who has "Been there, done that."

How does your car run on Tier 1 93 Octane we have here in South Florida?

 

If you simply want to lower the compression, and are only looking for a small bump, a thinner gasket would be in order.

A stock gasket is approx .051 or .055 at compressed thickness. I can't remember for the life of me off the top of my head. Anyway, lowering this down to say a .040 gasket will give you great quench distance. The quench distance is the distance between the piston and head while the piston is at TDC. On most stock LS2 motors from the 4 that I have seen measured the deck height was -.003 to -.006. The deck height is the distance the piston is either out of the block or in the block. A negative number represents a measurment of a piston which is coming out of the block and a postivie number is the opposite, the measurement until it is even with the deck.

To figure out quench distance you subtract the two. Example:
Deck height of -.005 and stock .055 gasket is and overall quench distance of .050. An optimal quench distance is from .032-.036. The smaller the number is reffered to as a "tight" quench distance. The closer the piston and head come together the better the "squish" or combustion. The better combustion leaves less unburnt fuel to pre-ignite, thus you can generally run more timing to make more power.

Joe G. used a Felpro 1041 gasket. It has a overall compressed thickness of .041. IIRC Joe's deck height was -.006 which gave him an overall quench of .035". A good overall quench which has allowed him to run up to 29* of timing, still make power in South florida heat without detonating.

In my last LS1 based stroker I ran the quench really really tight at .029. The car took alot of timing, but the motor was balanced, and blueprinted. On my current stroker motor I run a .036 quench.

Ok, back to your question about compression. The reason to do it before milling the heads is that you will decrease the overall flow of the "stock" head by milling it. If the heads are ported, different story. In talking with Tony Mamo he also went by this school of thought and his AFR heads are designed to flow best with all the material there in the head. In the heads and cam packages he designs he goes as thin as he can on the gasket (within reason) and makes the rest up in milling as opposed to using a stock thickness gasket and taking additional material from the head.

I guess it depends what your overall goal is.

 

I'm running 11.4 compression on 93 octane gas no problem. I have L92 heads milled .30 on an LS2 block.

 

I think I would prefer this method as well.
And this is all assuming the use of a stock or at least a 'not so huge' aftermarket cam choice in order to maintain piston to valve clearance, correct?

 

You betcha. Looking at the Crane 216/224 0.585" 114LSA. I want torque from 3000 to 4000, and I am not so interested in horsepower at 6500.

 

Doug, thanks for chiming in. Your recommendations have been spot on with my build! I run 27-29 degrees of timing and very little if any knock retard.

 

Hey Doug, I appreciate the education. I am looking at a budget build of a torque machine in the mid range (see my other thread at
http://forums.corvetteforum.com/show...php?t=2093341),
and modified 243 heads should fill the bill. It seems the Cartek does a nice job on 243 heads, and can mill or not mill the deck per the customer's specifications.

I think Cometic will be getting some of my business, either at 0.040" or 0.036".

 

Our 243 heads after being ported for an LS2 have a chamber volume of 61.5 cc with a .030" mill.

Using a .052 head gasket and assuming an out of bore piston at roughly .006" the compression ratio on a 6.0 liter motor is about 11.6:1.

If you were to run a .045 head gasket then the compression ratio is about 11.8:1.

Max

 

Thanx for the info, Max. Are the Cartek heads available with customer-specified milling? or with no milling? I would like to run a thinner gasket for a tighter squish region, but don't want to go over about 11.6 to 1 compression ratio.

Thanx, The Clevite Kid

 

We do everything in house, so we can do whatever it is that you want.

Max