Building a bowtie YJ

[BowTie YJ]

Found this site and thought it would be a good place to share my build. i am in the middle of a 4.3tbi/700r4 swap into an '89 YJ and to put it nicely, it's been a learning experience! The engine and tranny have both been rebuilt and I split transfer case and used the input gear and planetaries from a chevy case and used the jeep output shaft. i also intalled a SYE while i was in the case. i made the mistake of starting out with a 2wd tranny. Not the best decision when i look back on it! It has taken twice as long and three times as much money as i first thought but i hope it will pay off in the end. the best part of the build to me is the custom adapter that i designed and had a machinist build. i did it for about half the price of an off the shelf adapter. Everything bolted up but only time will tell if it was the right thing to do. I hope mating the chevy engine harness to the jeep fuse block will teach me wiring skills that will come in handy one day too! Some other mods include SOA lift and Rocky Road OTT steering. Check out my gallery and let me know what you think.

 

[CJ]

Don't let this guy fool ya... I think I know him from work!

Anyway... Welcome and by the looks of the pics in your gallery, the YJ is looking great. That is one hell of a front steering system you have there. Clearance is NOT going to be an issue...

I have to admit, the custom adapter looks like it works perfectly! Nice job!

Gallery pics here --> BowTie YJ - Jeep-CJ Gallery

 

[shamrock]

Looks good so far. I'm several years (more than I'd care to admit) out of the game of sticking Chevy's into Jeeps and such so I look forward to seeing the progress on this. My guess is that the wiring these days tends to be the most time consuming.

 

[CJ]

I know Painless sells allot of Chevy FI engine kits. Most of the time they work well.

SISy, did you buy a kit or swap in the existing Chevy harness?

 

[BowTie YJ]

No aftermarket harness for me. i insist on doing things the hard way! i am painstakingly deciphering both the GM and Jeep wiring diagrams and testing and connecting each wire individually. right now i have power to everything but the fuel pump relay. once i get switch power to the fuel pump relay i should be in business. there are still some obstacles to overcome with the gauges though. i am not sure if the jeep gauges will read correctly when driven by chevy sending units. on startup i will monitor oil pressure and temp with temporary gauges and then decide if i want to keep the original jeep gauges or go aftermarket, probably autometer.

 

[shamrock]

Times may have changed a bit so don't know if this is still relevant....generally I found it fairly easy to adapt a vehicles sending unit to the Chevy motor. Generally it took little more than a properly treaded fitting that fitted both the Chevy block and the new sending unit. At the time I was a 15 minute drive from Earls Supply in Los Angeles and they never failed to have something on their shelves that suited whatever adaption issues I may have had. Check them as a possible source if you decide to stay with the Jeep units and have any fitting issues.

 

[BowTie YJ]

thanks for the suggestion. i may be making this harder than it is but since it is tbi and the computer runs most everything i feel better using all the chevrolet 'stuff' since it probably all ties back to the ECM. i don't know if the jeep sending units would send the correct info to the chevy ECM. but as i was typing this i realize that your suggestion could be used. by reading the wiring diagram i found that the 4.3 chevy that i have has 2 temp sending units. one is for the ECM and the other is for the gauge only. the second could be replaced with the jeep unit and it's possible that my stock temp gauge could be used. all i would have to do is locate the gauge wires in the fuse block. it always helps to say things out loud. thanks for helping solve one of my problems!

 

[shamrock]

There you go...that just gave away my age....we didn't have to battle mating the engine up with the vehicles ECM....I doubt we had more than 10 wires to contend with back then. I keep forgetting how much more difficult these projects must be these days.

 

[CJ]

BowTie, grab the Jeep temp sending unit and the Chevy one. Using a DVM (ohm meter), measure the resistance from the terminal to the sending unit at room temp and record them. Heat up some water to about 100F, place em both in the water and let em come up to temp. Measure again... Then 150 Then 200 and so on. If the scales are relatively the same but the reading are different just place a compenstation resistor into the wire, if they are different scales, you can basicly do the same but only the normal operating temp will be correct.

Let us know,

 

[BowTie YJ]

the good thing is i kept the donar engine, sensors, wiring harness and ECM complete. i even still have the truck so if there is anything that i need i can just walk out and get it. so far it has been relatively easy as far as the chevy part goes. if it was swaping chevy to chevy, no big deal. it was simple just to plug everything back in where it came from. it was even pretty simple to get the computer mounted and the harness through the firewall. the hardest part for me (because of my lack of knowledge) is trying to make it look 'factory' and get everything to run through the jeep fuse block. it just takes a lot of time and thought to test what seems like 1000 wires with the key on, with the key off and at start. it seems the project has hit a wall it's so slow! if it was a carburated, hei small block i could have had it running a long time ago! not many wires to run an old small block and i have done a ton of those! this is my first computer controlled, tbi project. probably not my last though. i am enjoying the process. i think i also decided last night to buy new aftermarket gauges so the gauge testing point becomes moot. thanks guys.