MLS vs Composition Head Gaskets


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By napaunderground - 2 Years Ago
I'm debating whether I should go with MLS head gaskets still.

Does anyone have a strong argument against or for them? As it was, our engine had MLS when I took it apart.

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By DryLakesRacer - 2 Years Ago
If your surfaces are correct you should continue to used them. Not sure the style needing a rougher surface will seal. I also use them to control compression with their various thicknesses.
By Ted - 2 Years Ago
My own preference for stock or street engines is the Best Gasket composition head gaskets.  Having had coolant leakage issues at the lower edges of the heads with the Fel-Pro ‘blue’ gaskets, I avoid those.  If it's any consolation, Joe's 613 HP Y that was recently on the dyno uses the Best Gasket composition head gaskets.  The engine in my Y powered race car (8.90's @ 150 mph) also uses the same gaskets with zero sealing issues at 13:1 SCR.

You don’t mention the brand for the MLS gaskets as there are bunch of different ones out there.  Some of those MLS gaskets do get picky on what the RA or mill finish on the decks looks like.

Just my opinion so other comments always welcome.
By John Mummert - 2 Years Ago
Those head gaskets look like old school generic steel shim head gaskets to me. 
As far as I know only Cometic make MLS gaskets for y-blocks and those are not Cometic.
I don't feel there is any need for MLS gaskets with factory iron heads. Composition gaskets should be fine.
By napaunderground - 2 Years Ago
Thanks for the input all!

After researching I was again on the fence about MLS based on Ted's observation re:milling finish.

My main point in MLS was maintaining the highest compression ratio I could. I've gone from the stock 76cc heads to 73cc, I've yet to measure how much "down in the hole" the pistons are after getting everything re-machined. I suppose I could ask the machine shop...

I was hoping to not go backward just because I'm using a gasket that's thicker than what we started with.
I think I may go with the Best Gasket as I really don't want to have to redo anything. Just being "childish" about getting the highest CR I can get with what I got. It's just going to be mostly a utility truck for us, but my "more power!" internal child keeps getting involved. haha.


By Cliff - 2 Years Ago
I use steel shim 

By 2721955meteor - 2 Years Ago
I use the composition, no leaks .but I use grad 8 cap screws prefer the cat 1s,tho a bit more wok as some trimming required. I also run a bottoming tap  to all threads in block, and small amount of lube on new bolt threads. never any issues,tho  I have only over hauled 3 in the last year.. I also removed all the thin oil diversion plates, they happen to measure
the same as the comp gaskets  are thicker  than shim  head gaskets so rocker Armes are same geometry as shim style gaskets
the head bolts Henry used are not verry good, especially after ther use 1 time