It was a rolling change, so not black and white .... up to 89 SOME blocks with the boss for the oil return (not tapped) was still showing up (left from 88 TC, and 89 Merkur production). Basically when dual plugs appeared, you could say the boss was gone. All of the blocks can be modified, it's just specific to the cast in boss I'm saying here.Originally Posted by phillysrt4
The rumor was always they cast the blocks and weighed them. The heavy ones went to be drilled and tapped for Turbo production, the lighter ones went to the NA line. We have clearly seen that turbo blocks seem to have better, more centered bores in the castings than NA blocks. There have even been like 88 & 89 NA cars found with the boss drilled and tapped with a plug in them. Likely was set up as a turbo block then not needed ... .020 has effectively become the max overbore anyone (that knows the information) will do on a NA block (converted for turbo use) ... anything beyond that is risky without a sonic check for core shift.
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