I searched the archives and found a discussion of swapping a '97 850 engine that had an air pump into a 95 850 that did not have an air pump... however, I'm trying to do the opposite... swapping a '97 engine without an air pump into a '94 850 that has an air pump.

The old engine developed a pretty loud rod knock, and I had (have) access to another 850 engine so I'm doing the swap.

Here's the glitch I've run into though... the old engine had the air pump system, and the other engine that I'm swapping in does not have it. Initially I thought I could just swap the intake and exhaust manifolds, and that would solve the differences, but it seems the heads are somewhat different also. Specifically where the SAS valve goes into the head, there is no hole leading to the exhaust ports in the head on the engine that does not use the air pump.

Is there any easy solution to this problem? I've thought that I might have to also swap the heads between the engines, rather than just the manifolds. What would happen if I just went ahead and installed the engine with the intake and exhaust manifolds swithed, and not the heads? I'm assuming I might get some error codes that might mess with fuel trim... would it cause any serious problems with how it runs?

But I've also read posts where people talk about their air pumps not working and they consider it no big deal... so that leaves me wondering if going to all the trouble of swapping the heads is worth the trouble...

If there is anyone who has any insight or experience with these issues (engine swaps and/or air pumps), I'd very much like to hear your advice. Is there any alternate way of getting the air pump air stream into the exhaust?

The air pump is just used to get the catalytic converter warmed up to peak operating temp quicker. So you can really live without it unless you're in a state with polution control equipment inspections. But you can always just put it in for cosmetic pourposes.

Hey thanks for that reply! So it sounds to me like you are saying the air pump is not a critical issue as far as drivability and how the engine will run. If that's the case, then I'm not going to all the trouble of swapping the heads. I was going to go ahead and bolt the metal tube to the top of the engine and just remove the rubber o-ring/gasket so the air can just blow out around the tube (for cosmetic purposes, as you suggested).

One reason I was concerned, was that I read somewhere (Volvo Speed Site, I think...) that if the air pump sets codes in the ECM, then fuel trim is disabled. (Here's the site link: http://volvospeed.com/Repair/airpump1.php ).

That sounded like it might cause performance/driveabilty problems. But as I read more, at different locations, I found several posts where people acted as though the air pump not working really made no significant difference in their car's performance.

So I'm leaning toward just going ahead and installing the engine with the manifolds swapped, and not getting overly worried about the air pump.

Thanks again for your reply!