As usal, crossed to a few groups because there are some smart people in them...
I was at a machine shop the other day getting a set of brushes for the alternator for my '92 Grand Caravan, and I asked the machinist about my BHG. He said, "That's the one with the long 6 cylinder? There's only one problem with that. The head gasket can make indentations in the softer aluminium in the head, and a gasket won't seat properly. They make a "shim" specifically for that engine for this case, but it's expensive."
"How much?"
"It's custom made for each engine, so it's about $80..."
Eighty bucks? in order to seal the engine rather than pull the block for machining, etc etc? Sounds good to me!
doesn't this block have steel liners? if so, the argument about the gasket indenting it is b.s. - all you're doing is shimming the head to compensate for if it's been machined.
as an aside, while i think it's too late for you because you've had the head off this thing before, it's common for some aluminum motors, [specifically honda] to have sealing problems if the head's been off and the block's been skimmed. this is because the deck surface has an important feature most machine shops not only miss, but aren't in a position to replace, namely that the steel liners are set at a slightly different height to the aluminum in the deck surface.
[use mono-space font]
from factory:
___ liner deck ___|
vs. one that has been skimmed:
deck ___ ___ liner |
now this is not a big step, but you can feel it with a nail when you have the head off and it's been cleaned properly [without abrasives]. it compensates for the different thermal expansion ratios of the aluminum vs. the steel. as the aluminum expands, if there is no step, it'll lift the fire ring of the gasket off the steel and weaken the seal. and that's why once the head's been off and the block's been skimmed, they tend to fail again shortly afterwards.
rebuilders inadvertently encounter this problem when trying to race prep some honda engines. their solution is to machine out the whole cylinder/liner assembly and replace with a full cast iron retrofit - expensive and totally missing the point in my opinion.
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