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Old 11-27-2013, 05:06 PM   #1
Cali smog Nazi

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Howell TBI conversion question

Im acquiring an 89 4.2L manual transmission YJ, and have questions about the improvements this kit brings.

I have driven them, not often, and I understand how and why they work.
As a Cali emissions tech, and Jeeper I know the whole deal, except:

Has anyone installed one on their Jeep, and can you describe the affects before vs after?
Power and driveability gains?

I dont want to hear from any carburetor lovers, we all know you swear by your carburetors, but thats not me...

I am considering keeping this 89 and selling my '90 2.5L if the gains are worth it, thats alot of parts swapping after installing the kit (i want to keep all my goodies from my '90)....

Jeep TBI Products :: TBI KIT: JP1 Emission Legal Version CARB EO #D452 1972-80 CJ 4.2L Offroad - Emissions Legal - Howell Engine Developments, Inc.

Yes, I know, im speaking in YJ, but this issue covers all the 4.2L Jeeps...
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Old Jeep that was totaled (and SOLD!):
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Old 12-05-2013, 01:32 AM   #2
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My friend put this kit on his 88 about 1 year ago with good results. Starts up any day or temperature without problems, no need for adjustments at altitude change, easier time getting smogged, no stumbling or missing spots when accelerating, much better gas mileage at about 22mpg for his set up, performs great offroad and onroad, but not a noticeable horsepower increase compared to my currently carbed rig. I don't know if going with an HEI distributor is smog legal but that gave the best power increase for both of our rigs. Driving his rig very often has given me a good feel for it so take my experience as you will... I will be going fuel injection myself with this kit before I get my rig smogged again and as soon as I can afford the "smog legal kit"

And you had the link for the cj but you need the yj kit as there are a few very minor differences like wiring harness adapters and the smog same year or newer bullcrap with C.A.R.B. numbers I believe


Build Thread 1989 YJ, (Soon to come: TBI 350, 4l60) np231 sye/wide chain/6 pinion planetary, D30 ARB & Ford 8.8 ARB 4.56, 31" rollers for now, bds 3.5" springs, 1" Boom Shackles.
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Old 12-05-2013, 08:21 AM   #3
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I have just finished putting my second Howell system on. It's on a modified AMC 360 the first was on a '88 YJ. Both systems seem to work well. I didn't notice too much of a power change on the YJ but drivability was definitely improved. A week later we swapped the gears to 4.11 and that is what I attribute the power gain to. The 360 is a different story though. I had a Holley on it before the conversion and it was a tempermental sob on the trail. I changed it to the Howell and got a substantial increase in off road performance as it is seamless throughout the power band of the motor. I don't notice any fuel economy gains with the 360 but it's much more enjoyable to drive but on the 4.2l I gained a couple mpg but that also could be attributed to the gear change putting the engine at a bit higher rpm's as it originally had 2.73's which made it way slow on 33's. I don't have smog issues on either Jeep as Oklahoma does not smog test but the YJ already had a performance catalytic converter and exhaust system. I think that it would pass with no issues as it was tuned on a 4 gas analyzer. Best of luck to you I think for me it was money well spent and the wife is much happier when she drives the YJ as it is much easier to start on cold mornings. It was 20 degrees f this morning and both started like a newer Jeep which is a huge plus!
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