Mk IV vs. Gen V BBC

[Enginerd]

I was fortunate to recently buy 2 complete but dissassembled 454 cores.
One is a late 1980's Mark IV and one is 1991 Gen V block.

Which is better to build? Parts availability is probably better for the Mk IV, but the Gen V has an improved oiling system and a one-piece rear main seal.

I plan to use one of these to build a 496. Any opinions on which I will have better luck with?

Thanks

 

[big83chevy4x4]

the gen V has redesigned waterjackets and i believe you can only use gen V heads on gen V blocks. it you put a Mark IV head on the block the jackets overlap and end up leaking coolant into the oil.

i would use the mark IV block.

 

[k20]

Mark IV all the way. The gen V has compatibility issues. You can use gen V heads on a mark IV, but not the other way around. I dont even think the gen VI heads will work on the gen V

 

[4X4HIGH]

Gen V and VI are compatable but you can't swap GEN V or VI heads with a Gen IV in either direction because of the coolant passages.

I would built the Gen V engine if it were me. Gen IV stuff is what will start getting harder to find over the years and there are plenty of aftermarket Gen V and VI stuff available now.

 

[tiger9297]

The Gen V will have better cooling than the Mark IV. However, some of the old Mark IV heads are pretty good and can be bought cheap. If you go with the Gen V and want to upgrade the heads, you will have to go with a fairly new aftermarket head which will cost more money. If money is not a problem and you can justify a good set of Dart or AFR heads I'd go with the Gen V.

 

[Enginerd]

Thanks for the replys.

It seems as though we are pretty evenly split on the opinions about which block to use.

Any more opinions?

 

[mostwanted]

not to hijack, but...................

anyone else here of a problem with misaligned lifter journals on BBC's?