fred81292

Can i use any gm 3.1 front wheel drive engine. Just the block? I am going to swap my rwd stuff to it. Thanks

zs&tas

I believe the only issue might be the starter on the wrong side , you might have to drill and tap the other side , if there is enough material ? Blocks actually the same the 3.1 had longer stroke , just swapping the crank rods pistons will give you a 3.1 .

fred81292

Ok thanks for the reply. My 3.1 i believe has a cracked head. It overheated on the way home when i bought the car pretty bad. Will the heads work if i were just to swap them with new gaskets? Assuming my block is still good and not locked up.

zs&tas

You can repair cracked heads if it's not bad .

Yes you need to put the heads and up on the motor , the whole intake , I'm guessing the fwd heads are aluminium, they are different to your heads , so everything above will have to be swapped too.

Six_Shooter

iTrader: (2)

The FWD block is more different than just the starter location, which is a big issue for most swappers, by itself. Once the bellhousing is modified to clear the starter nose, you will also need to use a 14mm spacer on the FWD starter with the RWD flexplate/flywheel. Drilling the passenger side of the block doesn't exactly work, because the block is missing some support for the starter and will usually break because of that if drilled for the RWD starter location.

The mount pads are also different. Passenger side will sorta work, only 2 bolt holes more or less line up, the driver side is very different though.

Then there's the difference in the coolant passages at the front of the block. The RWD block has a bypass built into the front cover and block, that is missing on the FWD block. At the very least it requires plugging the hole in the RWD front cover, and should have an external bypass plumbed into a spot close to the inlet and the block drain.

I don't recall if the oil pan rail is the same between the RWD and (gen1/2) FWD block, I want to say it is, gen3 block it most definitely is different. This is a concern because you will need to use the F-Body oil pan to clear the crossmember, or modify a pan to be the same shape...

Your next questions about the head swap will be that you will drop the static compression ratio so much by putting RWD heads on a FWD block with FWD heads that it will run poorly at best and have little power. IIRC you'll end up around 7.5:1.
Going the other way, putting FWD heads on a RWD block, you'll end up with an SCR of between 11 and 12:1, which, yes is great for power, but makes it more susceptible to detonation. Then there's the fact that you need to use the FWD top end, that also requires the use of the DIS ignition system, which means that you need to have a crank trigger and the RWD 2.8/3.1 block is not setup for a crank trigger (RWD 3.4 is though, BTW), so an external trigger will need to be fabricated. This latter way, of using the FWD top end on a RWD bottom end is known as a "hybrid" and there's plenty of information on how to make that work on this forum and a few others.

fred81292

Thanks for the replies. There's a 3.4 firebird at the junk yard. Probably just gonna pull that if its got decent compression. That should be a direct swap shouldn't it? Using my harness and ecm and other 3.1 parts

drdave88

iTrader: (3)

Generally speaking, use the 3.4 long block and injectors, and everything else off your 3.1. Search it and you'll find a bunch who have done the swap before, myself included (though mine was a 2.8, but the same basics apply).

fred81292

Ok thanks. Just trying to get it running so I can swap my ls1 in my 89 chevy stepside. Then I can swap the car