It's very difficult to put the entire B234 into a 240, if that's what you're thinking.

First off, the motor mount brackets from the 740/940 won't fit in a 240, not even close. They don't even fit in a 'normal' 740/940, the B234 equipped cars had different front crossmembers. You can remove the balance shafts (plug the oil passages) but you'll still be making custom motor mounts.

Secondly - there's not any good way to move the distributor off the head (where there's a firewall in a 240). On a B230 you can merely pop the metal plug out of the block and see if the intermediate shaft has gear teeth (and swap the shaft if it doesn't, apparently sometimes you get lucky and the factory had a few too many 240 B230 parts when they built the motor) and put the 240 dist there. But a B234 has no intermediate shaft, no alternatives for the dist unless you go straight for the jugular and do some sort of distributorless ignition system.

Witha 240 - it's simply easier to take the part you really want (the 16V head) and put it on top of an 8V B230 bottom end, one that fits a distributor and bolts right into the 240. This leaves the more minor issues of coming up with a timing belt tensioner system (16V bolts the tensioner to the block, 8V to the head, the combination leaves no stock tensioner at all). Yoshifab.com sells a nice kit to solve that - using OEM Volvo parts (850 timing belt and idler, 960 tensioner IIRC).

The B234 intake manifold will also likely not fit well into a 240's shorter, narrower engine bay - it will point *right at* the brake master cylinder.

And then there's the way the 16V head hangs over where the block distributor on a B230 - the upward pointing cap won't work. There are weird 'crab caps' from other applications that point the wires all out to the side, though.

Oh, and while some people get away without doing it, you should probably get some valve reliefs carved into the pistons.

Here's a few random pics from my 16VT car:
Junkyard bottom end ('94 B230FT) with junkyard 16V head sitting on it:


Crab cap - I thought it looked a bit like 'Zoidberg' from Futurama:


You can see the bolt on timing belt tensioner setup from Yoshifab here:


I used an adapter plate (with plenty of porting on it, the head, and the manifold) to put a B230 intake manifold on the B234 head. Makes the clearance issues slightly better. Not 'solved' per se, but a little better.


Engine in car - throttle body uncomfortably clsoe to the master cylinder:


With some mild hacking I put a much shorter (and larger) 850 throttle body on the intake manifold - which gained an inch or two of clearance - enough for a nice elbow bend:


Had to hack at the throttle linkages to make the sit down further - when bolted to a 16V head the 8V intake is tilted up and mover to the left side of the car a couple of inches:


Turbo mounted down low, more or less in the normal position. I used a log manifold which is at least pretty compact and relatively affordable (compared to a custom-made tubular collector style), even if it probably doesn't flow as well:


All together. Drag strip trap speeds suggest around 300 hp at the wheels @ 14 psi. A little more than the previous 8V made (with plenty of supporting mods) at 24 psi.

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'63 PV544 rat rod, '93 Classic #1141 245 (now w/16V turbo)