SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: kenai on January 17, 2013, 10:38:03 AM
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Hi all- sounds like I may need new head gaskets; i have marine gaskets on now and they have not held; what should i check on the heads prior to installing new gaskets; should the heads be milled slightly to guarantee a flat surface?...thxs kenai
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wouldnt hurt to check the heads and the block out. slap a felpro on it and call it a day. dont forget head bolts if yours are TTY.
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I would check for flatness with a straight edge on the block and heads, check for cracks if not send the heads off to a machine shop and have them to that for u.
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Definately use a flat edge to check the straightness of the heads and block. More than likely is going to be the heads. And definately use marine gaskets especially if your boat sees any saltwater. Just my .02
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straight edge, not flat edge, lol my bad
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straight edge, not flat edge, lol my bad
I thought I taught you better than that Mark! :)
Make sure your mating surfaces are within .001 my 2 cents,
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While the heads are off, have them checked, maybe touch up the valves too.
I use standard felpro on my junk, one has 7 years (300+ hrs, sbc) on the rebuild, the other has 2.5 years, (~100 hrs, bbc).
Daniel
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Where are they failing, more importantly how did they fail (compression side or water side?)?
On a small block Chevy, the heads need to be smooth and straight and the block true. If they failed near the intake rail I would be suspect of the water pressures your running, if they failed in the compression area, I would suspect a torque issue, if the failed in numerous places, time to look at everything, literally..
I have used Fel Pro gaskets for decades and have never had a failure I didn't deserve.
If you want to put it out of your mind, Cometics and ARP bolts with hardened washers. ;)
GT
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Determine failure mode before determining solution. A very close inspection of the old gaskets, as well as the in leaned mating surfaces will give you clues. Why do you think they failed? Are the fire rings deformed? Which way? How did they deform? How were they allowed to deform? Any exhaust soot tracks on the head or block surfaces? All these questions need to answered before determining how to fix it.
On new builds where the surface finishes can be controlled, I'm a big fan of MLS gaskets. On repairs/rebuilds where the surface finish is not perfect, any quality composite gasket will work well, provided the surfaces are true, and critical areas are not pitted. High HP/nitrous/forced induction I would use MLS only and do what it takes to make the surfaces correct for that gasket. Chase (not with a tap) all the headbolts holes and use either new bolts with good threads or ARP studs. Even after things are machined, run a fine stone over the surfaces to remove any burrs. Pretty doesn't make it seal...flat and smooth does.
A lot of shops are using big ass fly cutters with a single cutter because they're too lazy to set the tool height of multiple cutters on the wheel....surface finish will suffer in these cases. Find a good machine shop, few exist any more, and the ones that do aren't cheap, but the difference is night and day. PM me for a recommendation. There is exactly one machine shop within 100 miles that I would trust doing work on my engines (besides me).
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ancient thread, but very interested in the above comment about exhaust soot in the gaskets. do some right now and unable to find for sure (to my knowledge) what the failure was, but the water jacket in the lower part of the gasket has soot crossing over the blue sealing lines. at least looks like exhaust soot - see it in other places on the gasket but does not cross the seal. is that really exhaust soot in the water jackets? And can compression leak out there?