Seeking help re: BB hi-performance heads which after being re-surfaced the intake manifold does not fit,obviously or not so obviosly the heads have been resurfaced too much.The machine shop says they only took off 20 thousands after rewelding cracked valve seats.Question,can I use oversize head gaskets (is this a good solution) to remedy problem after CC- ing to determine correct size of gaskets OR are the heads in need of replacement. Is there anybody out there who has been there??Any advice?
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Re: C2 858 Heads
Leonard------
Certainly, the removal of 0.020" is not excessive. Of course, one does not know how many "cuts" have been taken previously. The original steel shim-type head gaskets used for most big block applications are about 0.020" thick. A Fel-Pro Permatorue gasket is 0.039" compressed thickness. So, the switch to this gasket will "restore" the head "cut" most recently performed on your heads and this gasket is preferred for other reasons, too. Of course, as I mentioned, you still don't know if any earlier head milling has been performed. A cc test of the combustion chambers should reveal this.
You can also obtain soft copper shim gaskets which can be used in addition to the head gaskets. These gaskets, although expensive, will restore just about any head thickness loss.
Notwithstanding the above, I think that the bigger problem here is the "rewelding cracked valve seats". As far as future serviceability of the heads I'd be more concerened about that than head surface milling.In Appreciation of John Hinckley -
Re: C2 858 Heads
Joe - I ended up with a free 66 4 bolt 942 block in my quest for my current 66 942 block...it was a std bore block in great shape, but turned out to be overdecked to the point where my 858 heads (were virgin with no surfacing at that point, subsequently had an 0.008 clean up pass) sitting on top would not let the mainfold sit down to within .25" of the horizontal seal surfaces on the front and back of the block. In fact, the peg holes for the GM endseals on one bank the cut juste kissed the edge of the hole. I wrote this block off, and the original seller refunded my money minus the trucking (heads and block came from him). Anyway, I have assumed it was junk, but, maybe with the copper shims you mention it could be put into service again? Just curious about your thoughts. It is a perfect condition block in every other sense, almost like someone that didn't know what they were doing overdecked it....CraigComment
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Re: C2 858 Heads
Craig------
Yes, I think that these copper shims could be used to restore to functionality an over-decked block. Of course, over-decking also reduces the block deck thickness and strength and the shims won't restore that.In Appreciation of John HinckleyComment
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Re: C2 858 Heads
Yes, I was aware of that, but, the deck is still quite thick as these were fairly hefty cores. Glad I didn't throw it away in the process. Who sells these shims, are they available from Fel-Pro or are they a specialty item? Thx!....CraigComment
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Re: C2 858 Heads
Craig-----
They're manufactured by Milodon, SCE, and, I think, Fel-Pro ("HeadSavers"?). You can get them from Northern Auto Parts and PAW, among, I'm sure, others.
One thing, though: whether the block could be saved by using these likely depends on just how much excessive decking was performed. If the piston TDC position is much more than .005"-.010" above the deck surface, I'd be leery about doing this.In Appreciation of John HinckleyComment
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Re: C2 858 Heads
have the intake cut,i did it all the time to make it fit a decked block and cut heads.Comment
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Re: C2 858 Heads
Thx Joe - good points. I honestly don't know at this point how far past zero deck the pistons would go....but I will certainly check before I would throw out the block. Thx again!...CraigComment
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Re: C2 858 Heads
Thanks for the information Clem,your solution sounds the simplist, but if I just mill the intake to fit won't I run into problems like too much compression or the valves hitting. Did you like the suggestion to make sure the pistons do not protrude over 10 or 15 thousands above the block deck.Comment
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Re: C2 858 Heads
you need to have the CCs of the chambers done and that way you will know how much the heads have been cut. the 858 heads were 109 cc stock. no matter how far the pistons are out of the block you need .035/.040 between the flat on the piston and the head and this can be done with different head gaskets. if you have too much compression ratio the piston domes can also be machined down. the stock chevy specs for piston out of the block is .005. if you have any questions be free to call me at 724-468-5692 any evening after 9:00 est.Comment
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