While pulling the stock 1989 L98 w/ the 14101083 (casting#) heads to replace w/ a fresh 355 having the 3896962 (350/350?) cam, and early smog head (casting#) 3978487X (74cc?), we've now the dilemma of only one of three mounting holes on passenger side and old style valve cover gasketing.

Would it make more sense to freshen and use the L98 (083 heads) which are most likely 64cc? Since the pistons are (domed) TRW for 11.15:1 with the 64cc chamber, this may be too much on pump gas.

Has anyone added the two (drilled and tapped) blind holes for accessory brackets on earlier heads?? While they may not flow well, use of these 487X heads would keep the compression ratio within reason.

 

if you can figure out a way to adapt early heads for use with late model brackets you'd be the first.

 

Well the pad (mounting surface) are there on these particular older heads, just missing 2 of 3 blind threaded holes .

I was really wondering if anyone has experimented by merely drilling and tapping the two additional holes, and perhaps using a sealer on the bolts if the holes broke through into the coolant cavities, as done most often with cylinder head/block bolts?

The other unknown is if use of 93 octane will be sufficient for running this new combo having a static (calculated) compression ratio of 11.1:1. On the plus side we'll have more power, but that wasn't the intent---merely a cheap solid rebuild for a daily driver.