I have 2 motors that I'm thinking about putting on the street 90% and 10% race. Has anybody ever run the .095 Cometic head gaskets to lower their compression for pump gas. What's the down sides? They will never be full effort race motors. One is a 493" aluminum Indy block with -1 heads and the other is a 500" iron World block with -1 aluminum heads.
Thanks in advance for the input.

Where is your compression at right now?

Moving the squish areas of the head away from the piston usually increases likelihood of detonation. With an open chamber head it'd be a different story.

R.

The thickness of a Cometic gasket in no way diminishes it's ability to seal. If you look at the construction, they are obviously multi-layer. But even the really thick ones ,mostly have solid cores, with the thinner "sealing" gaskets on either side of this core. So if that center piece is .050 thick or .100 thick really makes no difference in the ability to seal

493" aluminum is at 13.46:1 and the 500" iron block is at 12.4:1. I have 2 other race cars and race motors so these will very seldom see the track if at all.

I don't think I would mess with those motors to lower the compression for pump gas with the head gaskets, I would run race gas in them and go for it It sounds like you have other dailey drivers so it isn't a case of you need to drive these to work and the store Besides everyone loves the smell of race gas on the street

I ran the .098 Cometic gaskets to lower my compression. I was 13to1 before and what ever it ended up I didn't care lol. I knew it was less.
I still ran C-16 for fuel lol. I did put 30 psi of boost to them and they did leak when I lifted the heads lol
I'm using a thinner set now on my new combo.
I had them change my gasket design and still had them in a week.

I got .125 inch. Downside is $400 for the gaskets. Never again.......

If you just plan to DRIVE it on the street, pump gas and even high compression is not a big deal. Anything will drive on pump gas, with the timing a little low. When you choose to stick your foot in it is the issue. So you would either need the timing to be really low all the time, or lower the compression.

At the Pump Gas Drags, we ran some really high compression stuff, WITH a lot of nitrous and had no issues, just had the timing really low. But that's a RACE scenario. For just cruising, it still be snappy, plus safe for the assorted blast here and there.........I would lower the compression

Monte,
would you lower compression by a thicker head gasket or do you think that is just a band aid. I just hate to mill the pistons down and re balance them. These motors have good part and I hate to be penny wise and dollar foolish! I just don't want to be running around all the time to chase race gas. I want to hop in and drive 50-100 miles. Both of these will always be NA motors. Like I said I have 2 race motors 583 Aluminum Hemi Indy 426-1 RA motor and a 583 B1MC motor for my race cars.
Thanks y'all for the input.

If you mill the pistons .040 to put them in the hole more, or put .040 of head gasket on it...........what's is the difference other than making the top of the piston thinner. I would run a thicker gasket and then you always have the easy option of returning the compression

Run E85 and keep the compression.

R.

If you have E-85 in the area(if its easy to find)
thats all I would do... change over the carb to E-85
which is probably about the same cost as the head gaskets
EDIT
this is based on if you have enough fuel pump to supply 30%
more fuel

x2=E85

The issue with E85 is the stations are few and far between. 2 within a 35 mile radius and one had water in their e85 when I ran it before. Also with the humidity here I had a little trouble and even tried blowing nitrogen on top of the tank when the car would sit for 3-4 weeks durning the winter.

The issue with E85 is the stations are few and far between. 2 stations within a 35 mile radius and one had water in their e85 when I ran it before. Also with the humidity here I had a little trouble and even tried blowing nitrogen on top of the tank when the car would sit for 3-4 weeks durning the winter.

U could do the old water-methanol injector trick. Just works when you nail it

E85 is probably your best option. I have just been running it for about 4 years. I just fill a 55 gallon drum for the track, but if I am driving the car on the street i fill up at the station if I am near it. I'm in south Texas, so same humidity conditions. I have not had any issues or do anything different than when I ran gas.

Thanks for all the input. I will order the gaskets and rest easy when I install them.👍🏻