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350 TPI v. Tricked out 258?

753 Views 8 Replies 2 Participants Last post by  **DONOTDELETE**
I have had this idea going through my head about swapping in a new tpi 350 from general motors into my 88 yj. The reasons being that I simply need more power in the higher gears (yes I have already reduced my axle gearing to 4.10), and want to stay smog legal. Will this approach work?

The other option I am considering is just building up my 258 (4.0 head swap), which already has a high flow exhaust and Mopar MPI kit. The engine has almost 140K miles on it but smoggs fine. Would a rebuild with the above upgrade give me the extra power I'm looking for, or would I have to do something radical. My only concern with this is that something that different would no longer smog, and more importantly, would loose much of the reliability in a basically good motor.

I have already replaced my suspension with the Warn Coil over, the axles with ARB Dana 44s, and tranny with the NV4500, so I think the rest of the system could handle the power generated by either option.

Any opinions or guidance would be greatly appreciated.


p.s. I live in a state that the smog issue is not that significant (Nevada), but could end up in CA where it is quite a bit worse).

1 - 9 of 9 Posts
How about a Magnum? Easier to wire, and direct bolt to the tranny.

I'm pretty sure that if your engine has the MPI fuel injection, you should be smog exempt in Cali already and it shouldn't be a problem. Joel

Your vehicle reads like a wish list for every Jeep owner except one thing is missing and that is a 350 TPI!

That engine is as refined as it gets. Dont mess with trying to piece together items that may or may not work well together...go for the complete package from the start.

I couldnt have been happier than the day I yanked the fuel injected 258 from my jeep and now in its place sits a fresh 350 TBI.

I emailed you a writeup from someone who has a 350 TPI in his jeep. He is a well respected, hardcore jeeper. He had a 'Cliffordized' 258 and now with the TPI in the engine compartment it feels like 2 of the 258's.


Larry 85CJ7, 350TBI ,T19 4spd
To LarryM. Re: 350 TPI v. Tricked out 258?

Hi Larry,

The Chevy 350 TPI is good engine, but what about other accessories (like alternator, power steering pump, AC compressor and air pump). But, you can't reuse all of Jeep's accessories or can you?

Also you mention in the past, if use 258 crank in a 4.0L engine and you get much more low end torque. Which spec should the engine rebuilder follow (258 crank and bearing or 4.0L crank and bearing specs)? Can you send me more info on this topic.


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To LarryM. Re: 350 TPI v. Tricked out 258?

Ideally you purchase a COMPLETE engine with all wiring, accessories, brakets, etc. An engine swap isnt for everyone and it is costly. The older jeep components like you mentioned are more than likely not usable with a newer Chevy engine. Have a look at the following link..

That is my 350 as I bought it a number of months ago. The picture shows it without the wiring but there was the complete harness with it.

Im not sure about the 258 crank in the 4.0 and I doubt I ever mentioned it to anyone here. Sorry.

Larry 85CJ7, 350TBI ,T19 4spd
In the same situation, I would opt for a magnum v-8, mopar, or stay with the 6.
But then I don't care for Chevys. I have the mopar swap in mine, simple and NO adapters. Steve

To LarryM. Re: 350 TPI v. Tricked out 258?

You could problbly reuse the alternator (Deco) and the (GM) PS pump.
I' not sure about the AC

To LarryM. Re: 350 TPI v. Tricked out 258?

Personally, I'd stick with the 258. Build it right and it will give you all you need, and then some, and still outlast most other motors. If you want even more power, there are several smog legal superchargers on the market that would give you a huge boost. If you're set on getting a V8 though, check out Z and M and their info on a Ford 5.0 swap. Its a much better motor for the Jeep than a chevy, and there are tons of smog legal parts available if you want to build it up even more. Plus, complete motors can be had for cheap from a wrecked 'stang! Again, I'd stick with the 258, but if you power hungry and want a 300 horse monster jeep, go with the Ford 5.0. Thats my opinion. Hope it helps. Happy Jeepin'!

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