A 1993 3.9 manual with 75k is available near me. I mainly want it for a parts vehicle for my 1994.

Besides air bag, will everything swap out? In the FAQ I notice a 5 hp difference in the engine.

 

AFAIK the only change was in the exhaust manifold. The 94 manifold is restricted they shrunk the diameter of the Y pipe and the exhaust down. The 93 exhaust manifold will fit the 94. I think that may be the HP difference.

 

The manifold needs to match the exhaust system; it's not a "Swap just the manifold" type upgrade.

Check the injectors; somewhere in there they changed the injector flow. Not a big problem; keep the ECU with the injectors and you're still good (so it uses the proper tables). I THINK they went with BIGGER ones in 1994; BICBW.

(And it's not that much bigger; it's within the auto-correct range for the ECU, but it takes out your adjustment for running changes.)

RwP

 

Good to know. Engine would be a big plus. Mine has 200k and a truck body in great shape

 

Here's why the '93 manifold won't mate up to the '94 Y pipe. The larger outlet is the one on the '93 manifold:

 

Yep.

Of course, if you move the whole exhaust system over, then the problem is solved.

Hence my comment - it's not just "swap the manifold", it's "swap the manifold and the entire exhaust system".

And I'd swap the manifolds, and either swap the exhaust or have a new exhaust system made, if it were me.

RwP

 

I got the larger exhaust on Rock Auto using my 94 as the search parameter, made by Walker. It is direct fit, from the Y back including CAT it was less than $400 delivered. You may need a couple extra u bolt clamps. It improved things and I never changed the 94 manifold. I wonder what it would do if I went with the 93 manifold assuming I also got a new Y pipe?

 

The complete exhaust was a bit larger in 1993 all the way to the back; you'd have to have a reducer in there, and that reduces (also!) the benefit of the larger exhaust.

I'd look hard at the whole thing.

GOOD news - you don't have to buy it all at one time! You can store the parts and just swap them on the designated day *grins*

RwP

 

The new Walker pipe is 2 3/4 at the end of the Y that meets the CAT. It stays that size all the way back. It comes with a short and a long reducer to make the connection from the CAT to the Muffler. I used the short one since I have the short bed.

 

I found a '92/'93 Walker Y pipe a couple years ago for about $140 I think it was. Unfortunately I think they've gotten much harder to find now.

The '92/'93 Y mated right up to the larger '92 exhaust manifolds, and the outlet was 3 inches O.D. I used a 3" pipe from the Y to a 3 inch in/out Magnaflow Cat. The Cat dumps straight into a 3 inch in/out Hush Thrush muffler, which is then reduced down to 2 3/4", and exits through the same Walker 2 3/4" tailpipe that onemore94dak referred to.

If you look on RockAuto, there is an option for a performance exhaust system (WALKER 17443 Dynomax Super Turbo Single System), which is the larger Walker Cat-back pieces. I just checked and it's currently showing "out of stock".