Cometic head gasket

Discussion in 'Engine Topic' started by Coadster32, Jul 29, 2020.

  1. Coadster32

    Coadster32 Veteran Member Lifetime Gold Member

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    I ended up having combustion gasses in the coolant system in my 79 Camaro, and had to take the heads off. (As it turns out, there was a 400 block gasket on my 350 motor.) I took them to a local reputable automotive machine shop for decking and a valve job/seals, and he recommended that I use a Cometic head gasket. Does anyone have any experience with these, or opinions on them by chance?
     
  2. flht99b

    flht99b Veteran Member Gold Member

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    Use Cometic MLS head gaskets on all the Harley engines I build. Intend to use Cometic head gasket once I figure out what thickness I need on the new SBC I'm building for my car. Quality product and good company.
     
  3. John Wright

    John Wright Veteran Member Lifetime Gold Member

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    I put those on my turbo sbc, but haven't filled it with coolant so I can't comment on how well they seal yet.
     
  4. G72Zed

    G72Zed Veteran Member

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    I have used these, great to correct piston to head clearances with custom thicknesses.

    Great quality HG, look into the required machined surface finish they recommend, it needs to be smoother (RA) than what a composition likes.
     
    Last edited: Jul 30, 2020
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  5. Coadster32

    Coadster32 Veteran Member Lifetime Gold Member

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    Thanks for the replies. I did a bit of research on this topic. MLS gaskets have been a round for a bit of time. Some claim they are revolutionary to this industry. I spoke with a representative from Fel-Pro this morning. Honestly, he was pretty darn snotty to me. Anyway his gasket would be 4.100 diameter. I told him my heads had "high capacity water jackets" that match the holes in the block, and asked if he had a gasket to match. He stated that the holes in their gaskets are considerably smaller to allow the water to flow better to the back of the block. The comparable Cometic gasket holes appear about the same, but the bore is 4.060 on that one. The heads are currently at a machine shop, and he recommended them to me, so I would have to say that he would get the surface finish proper for the gasket needs. The block deck is a really good finish as well. I pulled the trigger on the Cometic. I'll post up when all is said and done.
     
  6. muscl car

    muscl car Veteran Member Lifetime Gold Member

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  7. G72Zed

    G72Zed Veteran Member

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    I will add, in some cases if the blocks decks are less than acceptable, I have used 80 grit on a good straight block and "addressed" the decks to clean them up & bring them around and give the MLS some extra "bite" on the block side. Aluminum heads are always finished real smooth, and the "give" will be on the head side anyway, especially with aluminum, some castings more than others.

    Copper Coat spray can be used for extra bite.

    But, I will say in some cases in an Iron/Iron or even and Iron/Aluminum application, I went back to a Composite if the HG was correct for the build.

    Assuming your 350 is .030 over, be careful on the 4.060 Cometic's, bore chamfer and slight block core shift can get you close to having the HG overhang, and that's not a good thing.

    PS: The FP 1010 is a composition HG, and a good one at that.
     
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  8. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    Cometic's are good no arguments there. Especially of you are looking for an exact thickness for setting the quench.

    I've also heard good reports on these:
    https://www.summitracing.com/parts/nal-14096405
    if the thickness works for quench for you.
     
  9. cadillac_al

    cadillac_al Veteran Member

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    It sounds like a fairly stock engine. What's wrong with the good old steel shim gasket? I guess if you are 0 deck then the thicker gaskets is the way to go.
     
  10. Coadster32

    Coadster32 Veteran Member Lifetime Gold Member

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    The machine shop I took the heads to recommended the to me. At least an MLS gasket. With alum heads, he said it would be a better bet. It's a 383 stroker engine with aluminum heads/intake/headers/etc. Appox 10.5:1 compression.
     

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