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6g72 SOHC - Blowing Head Gaskets - Why?

Posted By: tdf46

6g72 SOHC - Blowing Head Gaskets - Why? - 02/14/18 07:56 PM

I have been trying to bring a 93 Montero SR back to life. Had the engine parts machined at a reputable shop a couple years ago. Blew a head gasket soon after the rebuild. Fixed that one and later it happened again. So, I have blown a head gasket twice.

During the last head gasket replacement I was careful to assure that the head bolts were NOT bottoming out before the torquing.

The heads were milled a bit by the machine shop. So, now my thinkig is that the compression is slightly higher than stock, and the stock head gaskets are not holding up.

I'm considering installing ARP studs (allbeit an expensive alternative to standard head bolts).

If anyone has other ideas about what is happening to cause this 6g72 SOHC engine to blow gaskets, I'm all ears!

Thanks for reading
Posted By: rxinhed

Re: 6g72 SOHC - Blowing Head Gaskets - Why? - 02/15/18 03:04 AM

Even the 4-cyl guy, me, can direct you toward the investigation. The issue could simply be false torque on the headbolts. The 3.0L (6G72) has blind pockets for the headbolts and often bottom out. Especially if the heads have been milled. you need to measure the bolt length, measure the gasket thickness, etc. There should be room left over for bolt and often isn't.
Posted By: tdf46

Re: 6g72 SOHC - Blowing Head Gaskets - Why? - 02/15/18 01:57 PM

I was aware of the "bolts too long issue" and that's what I meant by my second sentense above.

However, I will once again measure to make sure the bolts are not bottoming out before th torque spec is reached. Or go to studs. If I find a bolt length issue, is the best resolution to add a second washer or do I need to grind off the bolt (hardened steel) ?

Thanks for your reply rxinhed.
Posted By: rxinhed

Re: 6g72 SOHC - Blowing Head Gaskets - Why? - 02/16/18 01:35 AM

I guess I'm guilty of just reacting, and I dot not even see the big "NOT"....sheesh
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