Can I just swap motors from...

[shay_mcquaid]

my wrecked 1987 635 into my 1989 635?

I do know they are slightly different motors...

What would I have to be careful of or be aware of?

Any input would be appreciated.

-Shay

[Brucey]

if your build date is pre 6/87 they are very different motors and your '89 gearbox may not have the mounts on the gearbox for the crank sensors required to run the pre 6/87 Motronic.

If you swap engine types it is best to keep the engine loom and management with the engine.

It is possible to convert the earlier motor to the later management but there are lots of differences. For example you will have to fit the front pulley etc from the late motor to the early one and mount the crank sensor.

Mechanically you are better off keeping the 89 head and manifolds (the port sizes are different); also, different cam, bigger valves etc. Although it requires some work to match the head to the pistons (the combustion chamber is a different shape) you can get a pretty nice engine if you graft the 89 head and management etc onto an earlier bottom end and make it so that the CR takes a hike up from the (lower compression) 89 spec.

Pre 5/82 3.5 litre engines have a different bore and stroke BTW, which makes things more complicated still if fitting the later head.

cheers

[Brucey]

BTW the RH engine mount is different on pre 6/87 motors, and the block may or may not have the right holes tapped and drilled to accept the later mount.

cheers