I got it figured out for any of you that would want to put an m46/newer red block combo into your old 240.

I took the crossmember from the M46 car, turned it around, and drilled a hole in the other side (make careful measurements here). While you have the crossmember out, make sure you remove the return spring tabs (if present) on what is now the aft side - the overdrive unit will ride on them if not removed).

To reinstall, I got one bolt started on one side, and used a come-along on the other side to bring the holes into spec. I left the motor mounts unbolted so I could see how far I was pushing them but they remained flat, so there is not too much tension with this solution.

The M46 just barely fits the tunnel. The top has about ,75" clearance, and the sides also have about .75" clearance. We'll see if we get banging under hard acceleration, but since my motor mounts and trans mount are new, I don't expect it.

So far this has been the biggest problem in my conversion, but I haven't gotten into wiring yet ;)

-Phil

I'm not sure if the 75 was done this way, but on later models, there were three threaded holes in the floor pan on each side to mount the trans cross member to. If installing an M46/47, the cross member got bolted to the rear and center holes in the floor. If installing an auto AW70/71, the cross member bolts up to the front and center holes. NOTE: to find the unused holes I had to dig for a while with a screwdriver to get the dirt out of the way.

Not sure if this applies to the 75, but if it does, it might help you out.

jorrell
--
92 245 250K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently taking names and kicking reputations!

How good are your motor mounts?
If they are old and sagged it may explain the movement forward. IIRC the M46 should locate in the same place as the M41.
--
'89 245 sportwagon, destroyed by hit & run driver, RIP. '04 V70 2.5 T Sportwagon, 12k mi and '91 245 5-speed, 209k mi, replaced the '89

Pre-loading the motor mounts THAT much doesn't seem like a very good idea. I assume you are using the original cross member from the B20/M41 setup. If that's the case, I would be tempted to take the cross member to a wrecking yard (or maybe a Volvo specialty independent mechanic that might have a later 240 up on a rack) and compare the two. My gut tells me that when Volvo went to the B21/B23/B230 they were more likely to modify the cross member than the holes in the frame rails (which may have also been used as some sort of tooling mate holes during assembly = more costly to relocate). But I may be all wet. I'd still check it out before going hog wild with a rotory grinder. You're likely to run out of edge distance on the rear holes before you get everything to sit down in a "relaxed" position.

What about the front drive shaft length? Possibly one from a later year could be used there if needed?????

Good luck with the project!

Both the M46 bellhouse and the gearbox-part are a bit longer than the M41's, I don't know how the B20 compares to the B230. You could just measure the total length of both combinations.
There is some tension on the mounts, most from the weight pushing down diagonally. When lowering the engine I can line up the mounts by levering with a 2 ft pry bar, so it's not that tight.