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L18 Head warped

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Snowblime and I have been workin on his 521 with a L18. he blew a headgasket BAD. just turning the motor over with the starter would pump coolant into 3 cylinders and hydro lock the motor in 3-5 seconds. we pulled the head, cleaned it good and put on a new headgasket and it did the exact same thing. we were very careful to check the TQ and triple checked all bolts.He just took the head to a friends machine shop and said its warped out 20 thousandths. the head looks to be virgin. is it savable? should we be looking at something else as the problem? we couldn't see any cracks in the head or block. ???:unsure:

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If he says warped then it's likely warped. You can have it planed down smooth... but that's a lot to remove from both ends. Also a warped head can bind the cam in it's towers. Can you spin the cam by hand???... well with the rockers out?

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Can you spin the cam by hand???... well with the rockers out?


IF YES then the top of the head is flat.

then shave the bottom 15-20 thousants. done put Silver Seal cam tower shim in under cam tower to make up material shaved off. they come in .015 shims.



a good machine shop can pressure test the head to see if cracked. If intake ports were ported out to 1.5 froma a stock 1.25in head it could be thin and crack thus sucking in water.


be honest with all these L motors out you should or soembody should have a Free L16 210 head you could bolt on to conform this if its anything else major. For me My front cover cavitated and pump water past front cove rin the the oil pain.( I was steaming out exhaust thinkng it was head gasket also). I keep a spare 210 L head just for this trouble shooting.


be honest to me I think you would hydrolock 3 cylinders with just .020 out but it hasnt happen to me.




A 521 early L16 head will be ez enough to swap out


make sure intake bolts upper and lower are tight as you know the water passage from head to iintake so water could get sucked in there also

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Thanks for the fast replies. the first time we took it apart we noticed that the PO installed the intake gasket backwards so we thought that was all, but the new intake gasket didn't fix it. plus the head gasket was so bad that a square inch was missing. we will check to see if the cam spins ok. do you think we will have a problem with the combustion chambers shrinking too much? it's an open a87, doesn't look like it had any port work anywhere. going to take it to a different machine shop tomorrow and see about a pressure test too.

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chambers shrinking too much???????

dont know what this means but i dont think its going to affect anything. You just didntn want it to suck in water. weither small or not.I do think I have a spare L16 210 head but has no cam ,I think if you need one in a pinch as I probably will never use it anyways.YOu can have it.

253 653 3690 but I live in covington. plus dont gareentee it either.Datdoug lives close but dont know if he has spares, if need one sooner.

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What I mean is the combustion chambers shrinking too much and raising the compression. I know some people shave the head to gain compression, but this is a daily driver so we he doesn't want to raise compression too much. still want to run regular gas. Thanks for offering the head. I will give you a call if this one turns out to be junk.

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Just for fun....


If the head was high in the center and 18 thou was ground off each end to level it, the middle cylinders would be close to stock compression 8.43, the #1 and #4 would be 8.8 ish.

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Cutting .030 off an L head isn't much of a raise in compression with the stock pistons. Daily driver can easily be in mid 9s for compression without detonation.

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  • 3 weeks later...

Well we finally got it put back together. got the head shaved .023 and when we were putting it back on the wood block moved and we dropped the chain, so we had to pull the front cover. putting it back together I broke a bolt so it wouldn't seal! tore it apart and finally got it together again last night. Thanks for your help everybody.

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