scareyslo

building a 69 455 and it has the 10.25 pistons.Just wondering if the MLS gaskets are worth the big money,I believe the Cometics come in at .027 thickness. .Would like to keep as much compression as possible.but is thus $180 well spent?Or should I just go with the .040 Felpros?Running the Mondello Pro-Comps and a small cam,470-280 110

olds 307 and 403

Get the Cometic head gaskets with aluminum heads.

scareyslo

Any reason?

cutlassefi

For aluminum heads you can use just about any gasket that doesn't have a wire in the fire ring.
Cometics are good because you can get them in just about any configuration you need. I use Mr Gasket Ultra seals because all my stuff is surfaced with next to a 0 deck.

scareyslo

My real concern was if the difference between .028 compressed thickness of the MLS gasket and .038 of the felpro was going to make that much diff in engine compression to warrant the extra expense.I have the .038 gaskets in my 455 Starfire and it runs real strong with the 9.6 compression pistons,

olds 307 and 403

I believe some have had seepage issues with Felpro's on aluminum and the fire ring reacting due to different metals. It depends where your pistons sit in the hole as to which gaskets you want to use. It looks like about a 1/4 point more compression using the .027" Cometic vs basic Felpro's. You could buy the spray gasket high sealer on the cheap Felpro's for piece of mind. Hopefully those are Bernard Mondello Procomp heads. What duration is that cam? I assume 280 duration, what is the .050" duration number? I would measure head CC and where the pistons sit in the hole before ordering head gaskets.

olds 307 and 403

Here is a good compression calculator.
https://www.google.ca/url?sa=t&sourc...UMpa_LH40-ex3g

Run to Rund

I have used Corteco 55661 at .028" thick.

olds 307 and 403

The Corteco is the same as the Mr Gasket and Edelbrock head gaskets, Mahle owns them all including Felpro I believe, in .038 and .042". The .028" and .040" Corteco head gaskets are no longer made. I bought the last two .040" Corteco head gaskets from Rock Auto. I did blow one but was running 307 5A heads on an early 350 block without bushings, so there may have been movement. I also didn't torque the knock sensor. There are still some .040" Corteco's around.
https://www.google.ca/url?sa=t&sourc...UMpa_LH40-ex3g

scareyslo

pistons have just under.030 to the deck except #8 which measured almost .080 need to check the rod.Yes they are the Mondello Pro-Comps.Running them on my big ol 66 Starfire with a 490-280 110 cam and am really happy filling up with 87 octane for about 80 cents a gallon less here in Chi-town.Car is really strong down low and pulls hard to about 5200.then I chicken out and shift her

Run to Rund

I have several lifetime supplies of the 55661, could bring some to the OCA Nationals in Albuquerque.

olds 307 and 403

Rocket Racing also stocks .028" head gaskets, about twice as much as the Felpro. I have only used them on a iron head 350 though.

scareyslo

thanks,I think I am going to go with the .028 MLS gaskets.Maybee its only quarter point compression,but closer to half if you figure from the stock .017 gaskets that the 10.25 to 1 compression was based on from the factory.Dont wanna leave anything on the table.