Cometics are leaking
I've known a few guys to spray the copper adhesive on both sides of the gasket and let tack before installation, never tried it myself. Cometic is pretty specific about installing them dry.
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Well, after I cleaned the heads up, it looks as if someone cut the milling process short on the final pass. There is a .002-.003" rise in material and a deffinate "line" where it looks as if the operator thought the process was complete when in fact it wasn't. It's on the bottom corner of the head. The only thing is, is that the gaskets were leaking in the middle to the back region and were completley dry in the front where the rise is. I also noticed that the stain that the gasket leaves on the head shows a nice clean seal around the front cylinder, and about 3/4 of the next cylinder are sealed. It's at this point that the stain lightly goes away. The back 2 cylinders show a very faint stain were they were touching, but deffinatlly not a "sealed" state like the front. I just don't know what could cause the hole back of the head to not seat on the gasket.
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I'm down to a decision now and need some advice. I can clean, and copper spray the cometics and try it again, or I can use the graphite gaskets I have here and throw my quench off. I'm thinking of spraying the cometics and if they still leak, using the seal tabs that TS6 reccomended. What would you do?
If the gasket surfaces are slightly compromised I would scrap the Cometics and use a Felpro 1041 instead. It should clear your chambers (place it up to the head to check) and is far more forgiving than any MLS style gasket....plus the Felpro is .040 for better quench versus the older style factory gasket which isn't as strong and about .010 thicker I believe.
Good luck...
Good luck...
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Tony, I was under the impression that the 1041's were for large bores only. If they'll work on a 3.905, then I'll give them a try. My pistons were .008-.010 out of the hole, do you think that'll be to tight on the quench? I see where some people are running as close to .030 on quench, but I wasn't sure if that would be streetable or not?
Have you measured the bore diameter of your chambers? You might have to run a larger bore to properly clear the combustion chamber. Ive used 1041's on the dyno with no issues (when I was doing the early R&D work on the AFR 205 package), and I have read about a few people that have ran them on the street. The piston to wall of these engines are usually tight (.002-.003) which makes for minimal piston rock and the ability to run the quench tighter.
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From: Westminster, MD
Originally Posted by TS6
I've known a few guys to spray the copper adhesive on both sides of the gasket and let tack before installation, never tried it myself. Cometic is pretty specific about installing them dry.
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From: Shreveport, LA
Originally Posted by Tony Mamo @ AFR
Have you measured the bore diameter of your chambers? You might have to run a larger bore to properly clear the combustion chamber. Ive used 1041's on the dyno with no issues (when I was doing the early R&D work on the AFR 205 package), and I have read about a few people that have ran them on the street. The piston to wall of these engines are usually tight (.002-.003) which makes for minimal piston rock and the ability to run the quench tighter.
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I've used cometic .030" and .040" with copper spray sealant with good results. I don't like the 1041 Fel-Pro as I've had them leak coolant on N20 applications, although they maybe the only choice on a 4.125" bore sized block. If you were to swap from Cometics the only other one I'd recommend would be a GM Gasket, or a M.L.S. Fel-Pro if they are even available yet.
Are you sure the gasket was overhanging the cylinder? The bore size on the gasket should be 3.910" which should be very slightly bigger than the cylinder, may not be able to feel the difference since they run so close.
Are you sure the gasket was overhanging the cylinder? The bore size on the gasket should be 3.910" which should be very slightly bigger than the cylinder, may not be able to feel the difference since they run so close.
I had a water leak on 1041s after spraying it a few times as well. I'm still running them for now, but when the heads come off I'll probably switch either to rubber coated copper gaskets (like we put on ZAngel's car) or to a stock GM 6L MLS.
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From: Shreveport, LA
Originally Posted by -Joseph-
Are you sure the gasket was overhanging the cylinder? The bore size on the gasket should be 3.910" which should be very slightly bigger than the cylinder, may not be able to feel the difference since they run so close.
Everyone else, thanks for the input on the other gaskets. This is a No2 application, and I deffinatlly don't want a blow out down the road. It looks like the easiest and cheapest route for me right now is to re-install the cometics with some copper sealant. I had no idea the 1041's were so high $.
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I just got both heads back on. The copper spray is nice. I wish I knew about it before. No more smearing ultra copper all over gaskets, you can just spray some of this stuff. I don't see where spraying the adhesive could hurt anything. It sprays on nice and even, and the torque will flatten it out when you put the head on. Guess we'll see in a bit.
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From: Shreveport, LA
Originally Posted by twobit
Who makes the copper spray?
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I used uncoated cometics and stock headbolts. No problems thus-far (prolly 5k).
I could not believe how little they actually do torque down after 2 90 degree passes. I thought that I was gonna really have to reef on em.
I could not believe how little they actually do torque down after 2 90 degree passes. I thought that I was gonna really have to reef on em.