Topic: anyone done a 150 ci carb to TBI swap?? Help

[bobzoppa]

I just bought an '85 cj7 with a 150 ci 4cyl that uses the YFA electronic feedback carb. It's had 24 yrs of changes /modifications. Passed emissions but performance is bad, low power, doesn’t like to rev up –bad timing advance? Backfires, poor mileage, top speed of 50-55. and some parts missing.
Before I try to fix it all, I understand that in the '87 Wrangler the same 150 ci came with a TBI fuel system. Does anyone know if its a direct swap over??? Any write-ups on doing it??
Thanks Bob

[chardrc]

If you are going to upgrade to EFI you should probably go straight to mpfi off of a 91 or newer 2.5l. mpfi gives significantly more hp that tbi... i don't know much about the specifics about going from carb to efi but someone else should be able to fill in at least some of the info...good luck

[wilco40]

  Hey- Go to NAXJA forums or CherokeeForum, look for " XJ 2.5 YFA Nutter Bypass Plus" I'd have posted it here, but just found out about this site. Will cut & paste it here as soon as I can. Use the lower SMALL vac nipple on R side of carb for ported vac advance for distributor. Let me know how it goes. MERRY CHRISTMAS! wilco40

[dwtaylorpdx]

I'd go with either a Howell computer with a  with a Later TBI manifold and injector, or a standalone like a SDS but that would require a custom manifold activity.

Or see if you can find a Holley-Webber in decent shape. A 34/38 would do nicely... and avoid most of the issues with a full conversion.

Also I'd troll the Pontiac Fiero sites as their 4 cyl is the same lineage...

Dave

[chardrc]

I'd go with either a Howell computer with a  with a Later TBI manifold and injector, or a standalone like a SDS but that would require a custom manifold activity.

Or see if you can find a Holley-Webber in decent shape. A 34/38 would do nicely... and avoid most of the issues with a full conversion.

Also I'd troll the Pontiac Fiero sites as their 4 cyl is the same lineage...

Dave

in 84 jeep switched to the then new amc 2.5l 4banger from the "iron duke" that is found in the fieros so unless amc copied the iron duke rather than the more popular notion that they modified and shronk the 4.2l amc 6 cyl there isn't much linage... but you may know something about that that i don't (as you now what your talking about 99% of the time) 

[dwtaylorpdx]

I just meant the TBI technology, It will take some clever parts matching to get a manifold.
I believe CLifford used to sell a carb conversion for the old 4 cyl. But if an 84 has the std 2.5 then a
later model MPFI manifold or a 2.5 Carb Manifold will do it. I would NOT use one of the adapter plates to match
the Webber to teh Stock carb manifold, most of them the fit sucks...

Dave

[sharpxmen]

not sure if a TBI is direct swap (if you can use parts of your harness and just plug in the TBI portion), but i know that the MPFI would require both inside and engine bay harness or some serious electrical hacking - it is doable and probably in the end a better solution than TBI but it would require extensive mods. If you get the whole harness  from a YJ would still require some hacking inside the cab (i can think of dash lights, signals, warning lights or gauges, ignition contact harness, heater motor, dome/courtesy lights, speakers) and also for the engine bay you would need the distributor, alternator, flywheels and crank sensor + tranny bellhousing so you can mount the crank sensor and you will also need an extra hole for the PCM engine temp sensor (i think, unless the CJ has it and it's plugged) and the O2 sensor as well (bung welded in the downpipe would do).

[dwtaylorpdx]

Yea, I'd do the SDS or AEM standalone if I was after MPI, just less stuff to chase.

If you could find a 2 barrel TBI and manifold combo it might make a really hot setup...

Dave

[Jeffy]

necrothread