I plan on pulling the heads this week to do some cleaning/polishing/porting work & I was also thinking about maybe having them milled a little to help up the compression. A buddy of mine mentioned that I may be able to get a thinner head gasket that would raise the compression a little instead. Is this true? If so does anyone have a part number? This is for a 94 Z28.... Is this a good idea? How much compression is too much anyway? I will either be running the Hot Cam or a CC306, I mostly use Sunoco 94 octane & never use less then 93... I also plan on having a PCM tune after the cam install & head work, also installing coated long tubes and 4.10's at this time too.. Thanks guys!

 

Impala LT1 head gaskets.

 

Get A cometic.Best gasket on the market. Spelling may be wrong, but they are custom made, if needed, to assist in whatever you need. They are made to handle allot of pressure.

 

Hey thanks guys, I found this too!
.026 thick Mr. Gasket #5716 , They have them on Summit Racings site.

 

I ran these head gaskets for years....with no problems. You just have to open the water passages a little on the head gasket...which is very simple to do. Even the head gaskets AFR recommended I had to do this.

.015 thickness

I forget the stock valve relief cc's(I am thinking 4-7 cc)...but with an 54 cc combustion chamber, stock stroke & bore, .030" in the hole and a 4.100" gasket bore will put you at around 11.5:1 compression which is perfectly fine.

It will also get your quench around .045".

 

What are you refering to here?

 

The difference from the top of the piston @ tdc (top dead center) from the top of the block.

 

On an LT1 head w/ 4" bore (350 CI), every .006" reduction (head, or gasket)will = about 1cc in combustion chamber volume. Starting with 54 cc LT1 chambers, I believe a combination head milling and a .030 head gasket (.040 is stock) will be required to achieve 11 to 1, or higher. You can also find a compression calculator with a Google search and determine the compression, after you calculate your new combustion chamber volume. Also, check with a good performance machine shop, they do this all the time.

While you have the heads off, you should also have a three-angle valve job to further improve performance. And, maybe fresh valve spings and valve stem seals if needed.

 

Except they are VERY touchy about surface prep and therefore a poor choice for a project like(better suited to fresh builds) this AND the cheaper Mr. Gaskets are thinner yet and are actually even cheaper and thinner than the Impala gaskets which are still even thinner than the Cometics. The Cometics are something to look into for SERIOUS forced induction otherwise they are not worth the hassle and are not all that thin anyway.

Cantonracer has an interesting idea there.

The stock valvejob is actually very good if still in decent shape leave it alone.

 

MR. Gasket 5716's would be my choice, there are better ones on the market, but honestly for the price these work great.

 

Cool, But with Cometics you can get custom thickness

 

A steel shim(.015"-.020") gasket will require the same surface finish as the cometec's, those mr. gaskets will be harder to seal on a stock surface, and not hold as much pressure.

Stock lt-1 thickness is .051" I believe not .040" - thats the fel-pro replacement thickness.

 

Thinnest Cometics come in is .027 at least according to their own site, might be great for built boosted motors but those that think they are super thin and great just like advertizing too much even if not an add but rather articles. They are not that thin and are a PITA to use. I have heard of no serious problems with the Mr. Gaskets especially not for NA as Fat Boy is looking for, a lot of guys have used the b-body gaskets(Impala got the same LT1 as the rest of them) with the aluminum heads and some have had issues after some time as they are not really meant for use with aluminum.

Everything I have read puts stock aluminumhead LT1 gaskets at .049 and the Felpro replacements at .039.
Some guys on the b-body forum with aluminum heads tried Cometics at engine build time and ended swapping out for Mr. Gaskets with much better results, others are using them with stock shortblocks and BIG spray.