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Hello Garry,
Only the 4.0 and 4.6 litre engines share a common block, although as you mentioned, there is a colour coding system which ensured that Rover always used blocks with more metal between adjacent liners for the 4.6.
The last of the 3.9 litre engines featured a block which had the ability to be cross bolted, although the main caps and block were not drilled.
The caps were of the same design as those in the 4.0 and 4.6, but the crankshaft featured small journals like all other 3.5, 3.9 and 4.2 litre engines.
Only the 4.0 and 4.6 feature larger journal crankshafts, making their rods and pistons also incompatable with all 3.5, 3.9 and 4.2 litre engines.
Ron.
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According to "How to Power Tune Rover V8 Engines" page 23 the last 3.9 was the
"Type 6 - 3.9 and 4.2litre 38A-type "interim" blocks, 3.9 litre,3.702in bore, April 1994-October 1998 and 4.2 litre April 1994-April 1996-camshaft retaining plate, large cross bolted "38A"-type main caps(only the two vertical bolts drilled & tapped),10 drilled & tapped cylinder head bolt holes
Type 7 -4.0 & 4.6 litre "38A" blocks 3.702 bore, September 1994-2004-four bolt,cross-bolted main caps, 10 bolt cylinder head fixing, large main bearings,camshaft retaining plate."
Page 20-" What remains different about these'interim' 3.9 & 4.2 blocks is the fact that the main bearing tunnels are machined to suit 'small journal' crankshafts"
AND there are changes to crankshaft nose length etc in this period.
Geez, I feel like a Trainspotter. I only had a read of the book today as I was sitting supervising floor layers. Honest.
Regards Philip A
