gen1 vs gen2 blocks

[montess408]

hey guys way wondering what the differences where between the rwd blocks and the fwd blocks.
i know they are different gen blocks.but what is really different ?

thanks guys.

[Superdave]

Well, there are a few grey areas where Gen 2 blocks were used with Gen 1 internals.. like the TBI injected iron head 3.1 lumina vans

Gen 2 blocks are FWD only, Gen 1 blocks can be both (Early Gen 1's were in 86 and earlier Cavaliers as FWD).

Other than the mounting bosses and starter locations they are pretty much identical (other than the early Gen1's with the smaller main bearings). There were small revisions over the years but most things are the same.

[Guest]

IIRC the gen 2 had a strengthen lifter valley.

[1988GTU]

Most Gen1's do not have the crank sensor hole in the block.

[montess408]

as for the motor mounts can hole be driled in the rwd block to mount fwr and vice versa ?

[Superdave]

No, the bosses are cast different.

I think the bowtie block was set up for both but production ones weren't.

[montess408]

ok i see thanks dave!