Are all of these based on the same block?

It looks to me that the 3.1 is apparently a stroked 2.8 and the 3.4 is a bored and stroked 2.8.

Is that all there is to it, or are the newer 3.4's siginficantly different from our 2.8's?

Aside from the 3.4 having been recast, that's essentially it.

There are differences in application; typically in the cylinder heads/other intake, but many of the people here have experience in overcoming those in a Fiero installation.

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This should work until my site comes online....

All three engines are called Chevy 60 degree V6 engines (because the cylinder banks are 60* instead of 90* like the V8 small block). The 2.8 and 3.1 are the same bore, but the 3.1 has a longer stroke. The 3.4 uses the same stroke as the 3.1, but the block is a beefier casting and it's bored out bigger. The biggest difference in the Camaro 3.4 is that the starter is on the wrong side for FWD cars (and our Fieros), but this can be modified to work.

http://members.yourlink.net/dragon/parks/e-conv.htm