Thread: engine swap 3.9 to 3.5

Originally Posted by JohnF

I have a blown-up 3.9 V8, and have been offered a free 3.5 litre [minus exhaust and carbs]. Will all my fuel injection from the 3.9 fit the 3.5 without problems, and are there wiring isues in this swap.

Yes

Don't do it, you will not be happy with the lower performance of the 3.5!

1 yes
2 no
However another issue is how late a 3.9? If a vbelt no problem but if you have a later engine with crank driven oil pump , you will have to use the timing cover and accessories for the 3.5 as the keyway in the crank is longer in a 3.9 with crank driven oil pump.
You "should" also cut small cutouts in the heads so that the injectors get a clean squirt. It is obvious where to cut from looking at the 3.9 heads and it can be done in situ, with rags and a vacuum to catch ALL the swarf.

Regards Philip A

using the 3.5 will be like driving with the hand-brake on.

You will be very unhappy.

But if it is just to get mobile again until you find a good 4.6 block, then follow Philip A's advice.

Originally Posted by jakeslouw

But if it is just to get mobile again until you find a good 4.6 block, then follow Philip A's advice.

I agree, I think you won't like it but if it gets you going while you source either a second hand 4.6 or a good short motor to bolt the 3.9 bits onto then go for it