Thread: Engine swap advice please

I'm sure 89 was the first year of 3.9's and you should be able to tell by the engine number , i'd say either your wiring is in correct or being a 2nd hand motor it could be a dud.
Was the cam already in or did you fit it and do the timing, ignition timing could be out also - really there are numerous reasons why its not performing .

There's no point looking at the plenum top, the engine number prefix tells all.

Rover V8 Engine Numbers

Your EFI sytem would be the earlier flapper style and all of it would have been fitted from the original 3.5. You may gain some power fitting up the entire EFI and wiring system off a 3.9 but it wouldn't be a 5 minute job.

As for your 3.9, I'd be looking extra carefully at the cam timing, perhaps even finding another stock EFI cam to go in.

Thanks for the replies. How do i tell from the engine number that it's a 3.9? The new motor has a performance cam in it. The timing was set from specs in workshop manual. What is the flapper style, can you expand on that please? I had the heads recoed becuase of low compression. Previous owner ran gas. The bores were very good you could clearly identify cross hatching. I drove the original car it was fitted to before buying engine. It had more than twice the power even on gas. Can anyone tell me if the computer controls any other electrical systems? I have the computer, wiring harness, injection mainifold, plenum, timing case and all ancillaries for the later motor. I thought because my rego papers say 3.9 i assumed all of injection was.

Thanks bee utey i just realised that was a link for engine prefixes mine starts 23D04

Originally Posted by azastyle

Thanks bee utey i just realised that was a link for engine prefixes mine starts 23D04

Well that's a low comp 3.5 engine number for starters.

Your EFI system is built into the vehicle, most engine swappers just fit another engine to the old system.

A flapper air flow meter (MAF) looks something like this:



All the 3.9 engines were factory fitted with a hot-wire MAF instead which allows better airflow, looks like this:



To make the later EFI work you need the inlet manifold, injectors, wiring harness, ECU and all the relays and connections. It has been done by quite a number of people because of the increase in power. It isn't a job for someone afraid of wiring.

And also both the EFI systems control fuel quantity, the later one controls idle speed too. Your ignition timing is totally unaffected by either ECU.

I've got a modified intake with a near new Holley and air cleaner for sale...just putting it out there...Gary