Author Topic: Tbi to carb, 87 comanche  (Read 722 times)

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Offline SamsonJR

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Tbi to carb, 87 comanche
« on: February 10, 2019, 07:16:45 AM »
Hey guys, its been a while since Ive been on here. Heres the deal, have a 87 tbi Comanche these days, want to swap to a carb setup. The tbi has been nothing but problems and ended up frying the wiring to the injector along with some other stuff last night. Heres the plan- get a 160/180 cfm carb, make a adapter plate and  mount to intake read a artical before, the guy  grabbed a HeI dizzy for a 4.2, a reluctor ring and pickup coil from a v8  HEI dizzy, grind down the teeth on the V8 ring and used a 4 cylinder Chevy HEI cap. This will eliminate all the Renix junk. Anyone here done this, or have any input Im all ears. Im not interested in upgrading or repairing the Renix stuff. Id swap to Chrysler MPI if I had the time, but I have to get the Comanche back to NY in a month, currently in Florida.

Offline Jeffy

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Re: Tbi to carb, 87 comanche
« Reply #1 on: February 11, 2019, 02:31:06 PM »
I know there have been a few people who have reverted back to carb.  Clifford Performance used to make a Holley bolt pattern intake.  I seem to remember there being a carb'ed intake for '83/84 for the AMC 2.5L when it first came out in the CJ.

Haven't heard of anyone cobbling together a HEi though.  Seems like a lot of work for not much advantage over a decent coil or MSD.
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Offline dwtaylorpdx

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Re: Tbi to carb, 87 comanche
« Reply #2 on: February 15, 2019, 02:04:35 AM »
Just on teh carb VS EFI ,,, for long term...

I've had about 4 friends try and run carbs on the later engines.. Nobody was happy ,, like it or not the Renix injection has its warts,, but typically works fine,, but like any injection ya gotta maintain it,, I've had similar issues, eventually I bit the bullet and swapped the engine harness and ecu and the TB injectors and problems solved. .. Tried going carb and the disadvantages far outweigh the advantages.. Which basically there are almost none.

What I've run in to..
1. No carb will atomize Alcohol laced fuel across the power band and with altitude and temperature changes for street driving..
2. They corrode. Clog, foul unless driven daily, I highly recommend a carb drain valve and a drain hose for when its going to be parked for a extended time.
3. Mileage sucks even worse with the E10 fuel.
4. If you use  a carb that matches the power of the injection, your likely gonna see 10 or 12 mpg.
5. Unless that older cam is different that i recall,, The EFI cam doesn't make the vacum a carb profile cam does so the carb wont pull off idle right most likely.  (That's what I ran into.. )
6. When carbs were "it" fuel didn't have VOC limiters in it, the old gas evaporated like crazy. Take a cup of 100LL AVGAS or 104 unleadded race fuel dump it on a stretch of pavement in the sun, its gone in seconds, do the same with pump 92 E10, there will be a wet stripe for hours depending on the blend.. The part that doesn't evaporate is what gels up in a carb.

If you get it tweeked love to hear about it,, Especially if you figure out the mixture, you'll need a increase in jet size.. Timing and possibly degree the cam up a little.

Good luck..

The google HEI module wiring,, its very straight forward, basically all you need is a power wire to the distributor, Check out the distributor from a marine Pontiac 4cyl, as I recall they had a HEI trigger with an external coil.. (Been a while,,, ) you Might also look at the distributor out of the last year Fiero or similar, similar setup cause the 4 cyl distributor cap wasn't big enough for the Coil. A microsquirt will also run the whole thing with Coil near plug and it can run the TBI injector.. You'd be about $450 down on makeing that work, less with some pick and pull time... :)
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