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Discussion Starter · #1 ·
Hey guys,

Since my engine is apart, I figure I am going to get MLS gaskets this time. I am wondering if there are any pit falls on these gaskets. Is there a special deck finish required? Any kind of sealant needed on them. It seems like they could leak without.

Educate me please!

Chris
 

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Chris, we use a special head on the cutter when doing cylinder heads of this nature but I can't recall what it finishes off at. It is a very smooth finish though. Tomorrow I'm going to be at the shop doing some work and I'll talk with John, the owner of the shop, and ask him. I'll try to imprint it on my brain to remember. You do want to reskim the head though to insure it is flat and smooth. I'll try and get the details on that finish.

There have been some issues, although not widely know/could be rumor, with water seepage on the MLS gaskets. Not enough field information to verify why though. On our Aluminum big block Extreme Street car the MLS gaskest has been bulletproof. That car shoots about 4 lbs of nitrous per pass. So, as for being able to hold boost or 400-500 shot of N2O this has not been a problem for the MLS.

Another option that I tried this year is the Corteco White Seal gasket. So far after a couple thousand miles this year they have performed very well. I know a couple of guys shootin 400-500 shots with the Coteco's as well, without a problem.
 

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You do not use sealer on the Cometic MLS head gaskets. They do not need to be re-torqued. They are re-usable as well. You can get them in any bore size you want as well as many thicknesses. They have had no problem holding 12lbs of boost on my aluminum headed engine. I have heard of guys in the 20+lb range on them as well.

I don't remeber a special finish on the deck, but I did let the machine shop know I was running Cometics. The heads have the original finish that came from Dart.

Royce
 

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Discussion Starter · #6 · (Edited)
My deck surface is not just real smooth. It was decked to for flatness, but I have no idea on the smoothness. It is about like the surface of the Dart heads. I will have the heads rechecked while it is apart and check the deck as well with a machinest straight edge.

Chris
 

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RMS 36 is equal to a file finish or hone, it's not the finish that is all that important its the flatness. Check it for high spots near the edges of the block, many shops offset their milling heads half a degree or so to prevent the tool cutting on the backside of the cut and spoiling the finish. I always take a fine cut file and scraper to the head surfaces to make sure they aren't slightly high near the gasket surface edges. You would be surprised to find many are, even if it's only 0.0002" or so. Chamferring the bolts holes is a detail that should not be missed either.

Most people think a file and scaper cannot achieve as flat a surface as a milling machine but in actuality it's the opposite, using the proper draw filing technique and with some experience you can make a surface a lot flatter with simple hand tools than a machine can. For example lathe ways are all hand finished on the real expensive tool room models.

Check it out, these details are what separate the men from the boys when it comes to engine building. I'm willing to bet your heads are high on the edges of the casting which is causing problems because now the head is a spring you need to compress with bolt torque to get a seal, thats why it blew late. Took a few hot and cold cycles to stress the head bolts out and unspring the gasket surfaces. Just a theory.

The proper technique with head surfaces is to draw the file down the length of the gasket face and then at 30 degrees from both sides to it to get a nice crosshatch pattern all the way across. What you are trying to achieve is removing any highspots without removing any metal from the low spots.

You'll see what I'm talking about when you try it. ;)
 

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The August Issue of Chevy High Performance has an article on page 20 on these. It's really on the new Fel pro MLS head gaskets. They don't offer custom bore diameters, but it shows all the ones available and applications in the article. Also, it shows how to go about checking your block surface for the smootheness needed. It claims that these gaskets only need a 60Ra surface due to their rubberized surfaces. I really don't know that much about MLS myself though since I haven't used it, but I intend to use it on my nitrous small block I'm in the process of building, just looking for more info.
 

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Discussion Starter · #10 ·
Thanks guys, keep the info coming.

HG, MLS is Multi Layer Steel. Cometic, Felpro, and Mr Gasket all make them. I am sure others do as well. They are the new hot thing in head gaskets. They do away with the need for orings.

Chris
 
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