I'm looking to reduce the squeeze in my 440/493 and I was thinking of using a gasket THICKER than the Fel Pro .039 #1009 gasket. I have seen .051 gaskets on the 440 Source site, but has anyone used these? I am using aluminum heads with a compression ratio of 10.8 with the standard .039 gasket. A .051 will drop it to 10.5. Not a big drop but it may reduce chances of detonation in 100 degree summer driving. The .051 would help, and a .060 might be the limit as anything thicker may need longer pushrods, cause intake port misalignment, etc. I know that the easiest way to find this out is to call Mancini, but my west coast work hours make that difficult. Can anyone help?

LOTS of work doing that for .3 compression ratio ...PLUS you will lose power...

I would seriously consider WATER INJECTION

You want thicker? I think the Felpro 8519 (+ 2 #'s I forget which) (the std FP blue BB ones) are iirc .054". what is your quench?

.051 Felpro's are the thickest "off-the-shelf" gasket you'll find (about $150/pr from Summit, Jegs, etc.). No problem using those for your application. You could probably get thicker from Cometic but they'd be a custom MLS gasket which "should" have a finer finish on the block. They ain't cheap either!

If you have any cam at all in, you shouldnt need to reduce the compression. Your bascially at 9.3-9.8 to 1 with iron heads.

Plenty of guys run 10 plus with iron heads on pump fuel with no problems. Im at 10.6 with iron heads, no quench, etc. Timing at 34 total I have no problems. I do put a few gallons of 100 in it at the track.

cant you just back the timing down for the street and mix in alittle racegas at the track and bump it back up?

Depending on your cam, you might be able to get away with what you already have.

What is your piston to head clearance? If your running a .039 gasket & your pistons are .011 in the hole your at the very edge of effective quench.. Increasing gasket thickness could actually be worse... It may sound wrong but a thinning gasket could be your best answer if the piston is in the hole .011-.020... Beyond that & your not gonna help it with a thinner gasket.....



As mentioned tuning & water injection could also help..

Sorry guys, I should have included more info. I am running the '509 MP cam and have Edelbrock aluminum heads. It couldnt tolerate much more than 31 degrees of advance even when using Californias dog water 91 octane "Super" unleaded 15% ethanol gas. I used to run the distributor w/o the vacuum advance, but after reading articles in Mopar Action and from other sources, I ran a line to it and will keep it that way. The pistons are actually at .017 in the hole, and with the .039 gasket, I'm probably already at the edge of losing quench anyway, right? .039 + .017 = .056.
I ran the Cometic MLS gaskets a few years back and the car ran great. I believe they were custom made and .060 thick. I was able to increase the spark lead to 34 degrees and the motor felt crisp and responsive. I ended up pulling the heads when I found stem wear on some of the valves, and I couldnt afford to buy the Cometics at the time of reassembly. I had a set of Fel Pro 1009 gaskets so I used them instead.
A thread on the Race forum asked of the percentage of power gained/lost with compression changes. The consensus in the past was that each point is worth 4 % of power, EXAMPLE: An engine that makes 400 HP with 10 to one should make 416 with 11 to one. This of course assumes ideal cam conditions and zero detonation. The thread had many opinions and even some actual real world research showing the tested results to be lower than that, often in the 2 % range. I would gladly give up 2% of 500 horsepower to gain more streetability and to avoid having to pull the motor apart every few years!
The 440 Source website listed a no name .051 gasket for $15. I was a little suspect of its quality, partly due to the Wal Mart price and the lack of a brand name. Thanks for the help.

where did you run the vacuum advance line too??
Ported or manifold vacuum?

Cometic MLS gaskets can generally be cleaned and reused.

I would pick up a set of Cometic .027 gaskets or even consider going with the steel shim gaskets at .021 with the piston .027 in the hole either would give you effective quench especially the .021 which would put you @ .038 which is about ideal but I'm not a fan of steel gaskets with aluminum heads... The MLS would put you @ .044 which is near the top of where I'd like to see the #... .056 is just wrong, either less than .050 preferably less than .040 or plan on lowering the compression & timing quite a bit....

Have you had a AFR meter hooked up to know your air/fuel ratio?

Something doesnt sound right to me. I had the .509 in a 10.5 to 1 iron headed motor. I never had ANY detonation with that motor. Open chamber heads, so no quench at all.

Obviously you're on the edge. I don't know if taking your motor to 11.0:1 and improving quench will solve your problem. Maybe. If you ran a 0.060" gasket in the past and it worked better for you, at least you know the results.

You could also consider moving the the intake closing point, possibly in combination with the .051" gasket. If you retard the cam 4 degrees that will make a difference. Enough, I don't know.

Do you know what your current cranking cylinder pressure is?

You're problem is your cam choice , you already have little quench switching to the thicker gasket is the wrong move here .

I ran ported vacuum. This was during the last 100 miles before I pulled the motor for the teardown, so I didnt get much seat time to determine any fuel savings or driveability improvements. I am collecting the parts for reassembly now. I yanked the motor because of an oil burning condition. I have run the gamut with bad cams, a broken rocker shaft, valve stem wear and who knows what else. When I tore down the motor, I didnt find a smoking gun as to why it burned oil, but the machinist did. The rings were bad, and the cylinders were smoother than they should have been for a motor with less than 3000 miles on it. I had the cylinders deglazed, cleaned the pistons and I'm cleaning eveything for the re-rebuild. The rings and bearings just came in yesterday, and by midweek I hope to be ready to set the heads. NOW is the time to decide on head gaskets. I could simply default to the Fel Pro #1009s since I already have a pair.....

Little late but I would have had the block decked to zero the pistons....

Oil consumption is huge in detonation problems. I can't see you actual cranking number being more than 190 lb and with aluminum heads you should be fine.

I believe quench is less critical with aluminum heads than iron heads.
Quench should allow the same power at less spark lead than a less than perfect quench motor but I am sure people over rate it mostly on their magazine learnen not 100% the best sources.