I will be doing a head gasket swamp, and I hear of people using the thinner one from the Impala's because you can get a little more compresion.

Is there any negative effects of this, and is it a direct fit?

I would think having a thinner head gasket would be easier to blow out next time, incase it ever overheats. And what kind of gains do you see given the higher compression. How much higher are we talking?

People who have done it w/ experience please chime in...As I am contemplating the Impala or stock felpro.

Thanks,
Jason

 

I honestly don't know, however, I would go with the tried and true stock felpros. There are enough things that can go wrong without pushing it. JMHO

 

The impalas are a cheap way to improve compression as well as quench two things which would improve the burn quality. However I thought someone said something about the impala gaskets not working well with aluminum (please don't take my word on this they may work perfectly fine with aluminum) if someone else who knows could chime in please do.

 

What's the rest of your setup? If it's zero decked they will not leave enough piston to valve clearance. Very tight quench has become kind of a dick swinging contest. The stock LT1/LT4 has quite high compression for a pump gas motor and the stock quench is around 60 thousanths. Too tight quench = very bad juju.

Rich

 

Lol, well said

 

Just a note 60 quench is nowhere near too tight and he never mentions a rebuild ( nor does it appear to be in his sig) all hes talking about is a gasket swap going from standard aluminum headed fbody gaskets to impala gaskets. IIRC (rather if my notes are correct) the stock gaskets are .039 thick and the pistons are .035 in the hole which puts the quench are .074 not .060, the impala gaskets iirc are .029 thick so it would give you a quench of .064, both of these values are very safe. The number i typically hear for safe quench is anywhere from .030 to .040 so the swap to impala gaskets should be safe quench wise all the way up to the pistons being .011 in the hole, anything past that would get into the dangerous area.

 

My stock gaskets were .053 thick crushed.

I went with Mr. Gaskets replacements, thinner than the IMPY gaskets and made for aluminum heads. I think compressed was just over .030 but I can't remember exactley.

I'm sure someone will post the part number for these. I have had zero problems with them.

 

I really don't want have a valve float and boom my motor. Since 1.6 rr's will be going on w/ lt4 springs.

 

.053 crushed? that would put the quench at .088

Well the most important thing for valve float weather or not you go with a thinner gasket is that your springs can control it. keep in mind the ls1 stock has something like .047 quench area.

 

Stock f-body gasket spec is .049 but a measured .053 would not suprize me too much.

The few stock shortblocks I have measured the pistons were .022-.026 down though I have heard others report as much as .035.

Mr. Gasket 5716 is .026 and while spec'd for iron heads is a popular gasket with the aluminums. Packaging issues mean it is better to get the Victor Rienz 5898 far as I can tell same gasket but better packaging.

Have the Mr. Gaskets in my car now, cranking compression is nearly 230psi no problems.

 

The numbers I have are all based on what the blueprint would be, but I figured it would be further in the hole than blueprint not less heh

 

Yup, just make sure you have the clearance to get away with it.
I'm running .026" gaskets with my LE2 heads and LE1HL cam (> .600 lift) without issues.
Mock it up if you have to.

 

what's considered too tight?

 

I bought the Mr. Gasket 5716's, the head gaskets for the Impala, and am running them without any problems. Their right about the packaging though. Not very good engineering. The shrink wrap they seal them with to the cardboard peels off some of the coating on the gasket. I did like some recommended and put them in the freezer for a few hours and then took a razor blade and started cutting around every little hole and all sides to try and minimize the damage. Little still came off, but as far as I can tell no problems with them to this day.

I thought I calculated up the compression one time. Assuming you have 10.5:1 to start with, which if I understand correctly is the stock LT1 compression ratio, if I remember correctly the new compression was something like 10.75:1. Somewhere in that area. Anyone else know for sure?

If that's the correct calculations, how much RWHP would you think that would be? 5 RWHP maybe?

 

People have gone as low as 0.035". However - this is in a steel rod motor with very good rods and rod bolts. Meticulously machined and assembled with everything checked twice, then rechecked twice more. Does this actually work any better than the more typical 0.040-0.045". I doubt it. That's the engine builder dick swinging I was referring to. The reason the commonest gasket thickness is in the 0.039-0.041" range is that this is as tight as you should go in a typical, well assembled zero-deck motor. And it works. To go closer is a lot more work for questionable gain and a potential for a big downside.

Rich