Topic: TBI to carb?

[pioneer4x4]

First time posting, just found out about you guys. Let me introduce my self, I'm somewhat new to jeeps and am mildly mechanically inclined, try to do all own work. I have an 86 XJ 2.5L TBI ,auto tranny, (I know everyone has told me to sell it for 4.0,but Ive put to much money in it to sell at this point) that has been siting for quite some time and have recently rebuilt it, bored, ported, little bigger cam, header. Anyway Ive been told to swap the TBI for a carb. to get a little better performance, since the computer restricts the fuel and all that. I was just wondering what all i need to consider getting for this project. Ive read elsewhere something about the torque converter may be an issue,not sure. Will this be an easy swap since its pretty much an old carb motor,  I have a hole on side of block that is blocked off for fuel pump i guess thats a plus. but what about linkages and all that, Ive searched local junkyards in the past and have not found one 2.5l Cherokee anywhere to look at for comparison. So far I think my list consists of a carb kit, distributer not sure, fuel pump, intake. Ive looked in other posts and havent seen any one going from TBI to carb. its always carb to TBI or MPI. I think going MPI is too much not sure. figured carb would be easier. also i live in texas and have sniffer tests will the carb be an issue on that, not sure what year cars get grandfathered out of that. Any help would be much appreciated thanks for your time.

[aw12345]

why not simply turn up the fuel pressure on the tbi unit and see how it runs?

[chardrc]

i wouldn't go tbi to carb.. i ounce thought it would be easier... but you wont get as much power... and with all the ethanol and crap they are putting in gas these days its hard to keep a carb working right... if you are looking for more fuel output, you can increase the fuel pressure as stated above. or you can try putting in a bigger injector.. from research the tbi is very similar to the tbi units for Chevy's v'8s (except with only 1 injector instead of 2). but this is still speculation by me after some research and no first hand experimentation.

[pioneer4x4]

the TBI on this is non adjustable it is regulated purely by the computer. do you think i could drill a hole on bottom of regulator and insert some kind of screw to enable it to be adjustable, without leaking?

[chardrc]

here is a article about making the pressure regulator adjustable.. its for chevy but i believe it will be the same

http://www.thirdgen.org/tbi-afpr

i feel kind of bad giving this info without knowing if it will work / apply to the jeep but i think it will... so proceed at your own risk i guess... but unless you break a gasket it is free.

[pioneer4x4]

Thanks man Ill check it out.

[Mr_Random]

I have everything for an MPI conversion... If I make a decision on whether to rebuild or not, then I may be willing to sell all of it...

There are wiring problems you will have to confront, but it's MUCH better than downgrading to carb...

[aw12345]

I know for a fact that the tbi units on gm engines can be adjusted, its what Howell uses fir their Jeep 4.2l engine tbi converions and with a bit of work the regulator can even be adjusted without removing the unit from the engine. We had to do quite a bit of tinkereing with my buddies CJ7 and that conversion before it ran right

[Bounty Hunter]

Tune what you have or swap in a 4.3L, but don't downgrade to a carb.

[pioneer4x4]

does anyone know of a place that bores out these TBI's have only found people that work on 91+ TB's,

[Bounty Hunter]

A machine shop should be able to do the custom work for you.  If you pick up a spare, you could send it to me and I could see what I can do.

[pioneer4x4]

I ordered a TBI from california yesterday it should be in on Fri. thanks for the offer if i cant find some one locally ill hit you up and send some cash. will I have to get an new butterfly plate or is all the bore going to be on bottom half?

[Bounty Hunter]

To do it right, for the most gains, the entire bore needs to be opened up and a new larger throttle plate used.  This is what limits some when they do this themselves, as the plate is not round, it sits at 8º in a round bore.