Hello, I am on the hunt for a good used motor for my '87 EFI and have been offered a 94 3.9.
Can I use the block with my ancillaries or is it too complicated to use the GEMS engine as a base?
Any thoughts greatly appreciated
You can use any newer engine block. Starting around 1994 the crankshafts of all the engines got to be about 20mm longer in the front. If the newer engine has a longer crankshaft nose then you will probably need a crankshaft spacer and maybe a longer key for th shaft. Easy to get.
Also if the newer engine block does not have a distributor, then you will need to transfer all of your front cover and ancilleries to the new engine block.
Really it is no problem as the bolt patterns on almost everything is the exactly the same. It's just that the parts which bolt together got better and better over the decades.
OK thanks for that. I am concerned because my mechanic tells me that the front cover is heavily worn around the oil pump from dirty oil and lack of changes and that is one reason why my oil pressure is low. He wants me to use a better cover in the new engine.
I suppose then that I can also use all my ancilleries including my 3.5 plenum chamber which does not have 3.9 marked on it, so that visually it all looks like a regular 3.5.
Basically everything bolts up to the block. Doesn't matter which side of the block it's on. You really should replace the oil pump when you change engines. Some of the oil pressure losses are probably related to worn out bearings which are hemoraging oil.
The "intermediate" front cover has a much better oil pump. If you use this cover then you have to use everything off the front of an "intermediate" engine as well. There would also be quite a lot of custom plumbing to get things hooked up to your truck. Very doable though.
There's no such thing as a 94 3.9 Gems. If it says 3.9 on it, it's Lucas, and will go in without modification( though, as I said before, you 'should' use the ECU that came with the 3.9, 14CUX). Gems came out on the 4.0 in 95 (96 in the US)
1 - 7 of 7 Posts
This is an older thread, you may not receive a response, and could
be reviving an old thread. Please consider creating a new thread.