1988 2.5L to Pre-1990 4.2L

[jmyers]

336000

This one is for all you motorheads who have already been through this! I'm going to replace my 1988 2.5L 4 banger with a pre-90's 4.2L. I'm thinking to do an entire swap I need the following: Engine, Transmission, wiring harness and radiator. What do I do about engine mounts and are there any problems anyone can foresee with this swap? I figure if I go with the 4.2L I will not need to worry about EFI. From what I am able to find out I believe the 4.2 is not Fuel Injected. Also, do I need anything to connect the Manual trans I'm transferring with the 4.2L to the transfer case? Any help at all would be appreciated.

Thanks

Jon

 

[BigBadYJ]

337000

Hey man, I dunno if i can help ya much, but i'll try. When i bought my 88 YJ it had no engine sitting in a corn field. But it origanally had a 4.2L. You can't find them anywhere enless you wanna pay to get a rebuilt. What i did was buy a 4.0L out of a cherokee(94) the engine mounts are the same and the transmission i had bolted on. Your transmission will be different because its a 4 banger but you can get a transmission and engine from the junk yard if you shop around, but you wont find a 4.2 I searched atleast 150 junk yards and never found one. Hope this can help. I have tons more if you want it. E-mail me at danny@dudleyfamily.com

 

[jmyers]

338000

Thanks dude! I fired some more questions to you at your e-mail address!

Jon

 

[ManglerYJ]

339000

Actually, the 4.2 is available in quite a few things, but the problem is finding one that is good shape. AMC put them in just about everything (Hornet, Gremlin, Eagle, Wagoneer, J-trucks, CJ's, etc.), so you are better off finding someone who is parting one out.

You will run into a couple problems with motor mounts. The 2.5 motor mounts are farther back on the frame than the 4.2 ones. Nothing some cutting and welding can't solve. The 2.5 liter is TBI fuel injected, so you will have a problem with fuel pressure going into the 4.2. THe carb in the 4.2 needs like 6 psi fuel pressure and the fuel pump will be putting out around 14. The regulator may handle that, but I'd get a spare fuel pressure regulator and have it handy if you burn yours out.

For a transmission, you will need to swap in a 4.2 transmission such as a Peugot (YUCK!), an AX/15 (better, but will require a matching t-case), a T-176 (medium duty 4 speed transmission), or a T-18 (heavy duty 4 speed). There are a LOT more options with transmissions, but it depends on what you can afford and what you want. Personally, I'd go with an auto transmission.

I'm not sure what you are after going to the 4.2 liter. If it's horsepower you are after, you will not get any more than the 4 banger from a 4.2. THey are rated at the same HP. However, the torque from a 4.2 is phenominal.

THe easiest swap is a 350 Chevy swap into a Wrangler. All the parts you need are commercially avaiable from Advanced Adapters, 4WD Hardware, and others. I have a 305 Tuned Port Injected Firebird motor in my 90 YJ and I love it. It was a lot of work, but I did it the cheap route.

E-mail me if you need any further help. ManglerYJ@aol.com