I am swapping engines on my 89 745t
I found a used 90 B230FT engine to replace the old one which was toast BTW
The volvo mechanic who sold me the 90 motor said it should just drop right in without changing anything.
The mechanic who is dong the work said he wants to change manifolds to stay with the original manifold from the old engine.
I dont understand the logic in changing manifolds since they seem to be identical

Any advice is most appreciated

Your mechanic is partly correct. The 1990 engine will bolt in, but you must change the throttle body, distributor, and Idle Air Controller. You will use the engine wiring harness from your 1989 car. While the Coolant Temperature Sensor is different, the LH 2.4 Coolant Temperature Sensor works fine on LH 2.2 engines. The later injectors are also different, but they work fine on the LH 2.2 engines.

There is no reason to change exhaust or intake manifolds unless you buy an engine without turbo. In that case you will move the exhaust manifold and turbo assembly to the replacement engine.
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john

I expect your mechanic is talking about the exhaust manifold, not the intake manifold.

And I bet the engine you bought did not come with a turbocharger on it already - your mechanic is probably taking the turbo off your old engine and putting it on the new one.

I understand that the exhaust manifold on the 1990 and newer cars is a more efficient design than found on the 1989 and earlier cars. It's supposedly good for an additional 10 hp. However, I believe that the new flange was designed to fit the smaller Mitsubishi turbos that came in 1990 and newer cars. I bet your car originally came with a larger Garett T3 turbo, which doesn't bolt up to the new design manifold without some machining.

So, your mechanic probably wants to take both your turbo and your exhaust manifold (they are bolted together anyway) from your old engine and put them on your new engine. The bolt pattern is the same to fit both old and new types of exhaust manifold to any year B230FT engine block, so that would be the quickest fix to get your old turbo onto your new engine.

However, maybe your best option is to keep the 1990 engine's exhaust manifold right where it is, and have your mechanic adapt it to fit your Garett T3 turbo from the old engine. It is a fairly easiy job for a machine shop to mill the 1990 or newer exhaust manifold to bolt up to the earlier (and larger) Garett T3 turbo. If you post this question on www.turbobricks.com, several people can reply with their personal experience, adapting the 1990 exhaust manifold to fit a variety of turbochargers.

There is a good chance that he has a Mitsibishi TD0-5 12B, which requires much more modification to mate to the 90+ manifold than does the Garrett.

Thanks for your comments
I failed to mention that this engine comes complete with turbo, AC pump, Alternator and starter as well as the original wiring harness.
It is a plug and play machine. The only diference is it is from a 1990 volvo
The Volvo mechanic who sold it said it should just go back in with out any modifications.
The wiring harness should plug into the old harness and all the lines should be the same.

If anyone hans any expereince with thisd kind of a swap that is diferrent, I would appreciate hearing about it

The 1990 engine wiring harness does not interchange with the 1989 chassis. You must use the 1989 engine wiring harness.

If your AC works, don't use the new AC compressor. Just take the compressor loose and let it lay on the chassis while the engine is replaced.

As I wrote before, change the throttle body, distributor, Idle Air Controller and drive away.
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john

Great
Thanks John
I will pass that on to my mechanic

"I dont understand the logic in changing manifolds since they seem to be identical..."

That's a question best put to the mechanic who asserts that the manifold should be changed.

A good rule of thumb is, "If it ain't broke, don't fix it."

Likewise with the manifold.
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Don Foster (near Cape Cod, MA)