I hate to cross post forums but I'm needing help. I have been searching the internet all night and found nothing so far. I dd post this other places on the web, so if you see it you can just ignore (sorry)

I started installing my heads, and started to question the gasket. It is supposed to be .029 thk Impala/Caprice LT1 head gasket. The GM part No. is "GM PART # 12553160". This gasket is a confirmed .029"

However, my problem started when I decided to do a cross reference and buy the Fel-Pro brand (Fel-Pro part no. 9966 PT) instead of GM. The gasket appears exactly the same physically, but I can't find and specs on the gasket, and I read on LS1/LT1 Tech that the Fel-Pro Impy Gasket was .049. That would really suck!

The other thing I noticed about these gaskets, is that most of the coolant holes in the gasket are very small relative to the large coolant passages in the head and block deck.

If you guys have a way to find out the thickness specs on the Fel-Pro 9966 PT Gasket I'd appreciate the help big time. I have one bank already installed and torqued and really don't want to remove that head if I don't have to.

Thanks for any help - comments or suggestions

I'm not familiar with that part number. The 1074 Felpros I run are .039".

Yeh, I was going to use those, but Lloyd Elliot, the guy that ported my heads, said to use the thinner gasket as it would give me a pinch more compression and since I have such a narrow lobe separation on the cam it would help out.

I did a little hunting too but was unable to find out. I can confirm that the GM Impala gaskets are indeed .029" when compressed, having measured them after removal. One would think that the gaskets you reference, since they're listed as for the Impala and similar LT1s, would be very close to that too. But who knows? I share your frustration. When I want to know something, I want to know it, dammit!

This really pisses me off, because now I'm gonna run down the Chevy dealer in the morning and spend top dollar on the GM gaskets if they even have them in stock. Then I got to come back home and pull the head I spent so much care torquing to spec and then reinstall a gasket that might be the same as the one I just removed!!!

Well then measure it after you get it off, then you'll know.

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That makes me feel good!

Several threads I found on cz28.com indicate that that is the stock-thickness Al-head replacement (i.e., 0.049)

The preferred .02X gasket is the Reinz. The Mr. Gasket has been used by a lot of people but has packaging problems that cause it to rip when you open it.

While plenty of people have used the GM Impala gasket, it is not intended for use with Al heads so some think it may lead to corrosion problems long term.

Grizz, Ill check with my machinist tomrrow and see if he can come up with something as far as info you need.

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Vis,
I think I remember reading this somewhere once as well. I guess my worst case is losing the two hours I spent installing the one head and one gasket. It could be worse! I'll check out the Reinz gasket. I remember someone else using that one. "Shoebox" over at cz28.com claims he has used the gasket that I have installed for several years with no problem, but then again it is still may be too thick for my intended use.

Thanks for the reply - I'm meaning to hit you up on some tuning tech issues later on too! take care

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That would be great. Thanks

You only have one head on so far, correct? Well what is the uncompressed thickness of your other 9966 gasket? These gaskets only compress a few thousanths so that would give you a very close indication of your compressed thickness. For example, the GM Impala gasket is .036" as it comes out of the package and of course as we know is .029" installed. Sorry I didn't think of this easy solution to your dilemma sooner.

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Head gasket not returnable if opened. I cut a tiny slit in the shrink wrap and measured one end. I measure betwenn .053 and .055 - these must be .049 compressed.

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Yep, that must be their standard aluminum head replacement gasket. Well now you know, anyway. BTW, I never had any problems when using the GM .029" w/ aluminum heads. The only reason I use the .039" now is to get my quench exactly where I wanted it with the stroker which is zero decked.

Well, I just had a guy on cz28.com confirm the thickness of the 9966 PY to be .049. He said he measured them; this confirms the thickness at .049 - now the 60million dollar question is who makes a good .029 gasket?
GM Impala Gaskets - do they have issues?
Fel-Pro makes the FP-1074 which is .039 but I don't see them making a .029 one.

Stick with the .02x if it's a stock shortblock.

Here is what I have uncovered so far with the help of a lot of folks here and elsewhere. The Fel-Pro 9966 PT which is cross referenced all over the place as a replacement head gasket for Corvettes, Camaros, Caprice, Impala and others is a .049 compressed thickness gasket. No matter what thickness gasket those cars came with, this is the one you will get if you go to your local parts counter and ask for a gasket to fit.

With that solved I asked Lloyd if it would hurt to leave the thicker gasket in place. I also emailed CFI-EFI with a bunch of questions and he also confrimed what Lloyd had sent me.

[color=blue:1b80af28a8]Lloyd Replied
"Don,
You will lose almost 1/2 a point of compression with the thicker gaskets and make the quench a lot looser hurting combustion efficiency. That equates into about 10 RWTQ and 10 RWHP across the board and the engine will be MORE likely to detonate due to the looser quench.

I would get the GM Impala gaskets or the Mr gasket 5716 head gaskets (.026" and even better). No worries about using them on alu heads. They just have a steel fire ring as opposed to a softer (copper) fire ring. The only thing the steel ring will do is brinnel the head (leave a VERY small indention) where the fire ring sits and if you remove and install the heads several times on different engines, you will eventually need to surface them sooner than if using the gaskets with copper fire rings.

Lots of people use them with no problems on alu heads.

All of the gasket will have smaller holes for oil/coolant but no worries as it is fine.

No corrosion will happen as long as coolant is used. If using only water, it can cause aluminum to corrode regardless of gaskets used.[/color:1b80af28a8]

I also had "Vis_Crosceus" put me on the Victor Reinz path and I dug up a part number for .026 compressed thickness gaskets from them as well.
Victor-Reinz 5898 is a .026 gasket.

Now I'm looking for any of these usable gaskets locally, but it looks like I'll have to order them.

Thanks again

NAPA carries Victor-Reinz. What they don't have in stock they can usually get overnight. There's a lot of good info in this thread. These gasket numbers and their various thicknesses should be added to the tech sticky once this is all sorted out. It's a very popular subject.