'74 J20 with a GM drivetrain 4.3L/700R4/NP208

[AwesomeJ10]

We purchased this ZZ code J20 back in September 2012 with the intentions of building it to be a tow rig. It had a rebuilt AMC 401, TH400 and QT. The TH400 wasn't working correctly and the QT had a kinds of slack in it, so we ended up swapping the 401 into the waggy and selling off the tranny/case to another board member.

Then it sat in the driveway for a couple of months while we completed the 401 swap into the waggy and did some work on the Honcho. Well I was DD'ing the waggy and was getting 10MPG in the TBI 401. So it occurred to me that a little V6 would probably get better MPG's than a 401, so the search was on.

I found this '93 4.3L V6 complete with 16144288 ECM, harness, all accessories and radiator for $500. I already had a '89 suburban 700R4 with matching NP208 that I had picked up for $200.

Built a little stand in the garage to hold the entire assembly together, then connect the radiator and ran the exhaust out the bottom of the garage door. Got all the wiring connected and actually ran the engine on the stand.




Then we installed the entire engine/tranny/case as an assembly. Had to remove the hood. but the grille remained.






and here is the final product

[AwesomeJ10]

So then we finally got everything going and took it on a little trip. Decided to check out the brewery in Estes Park CO.

Few pics of the drive up. Temps were in the single digits.







Then at the bar


Then a little 'wheeling on the way down.

[AwesomeJ10]

Initial impressions of the 'new' drivetrain;

First of all WOW. That little V6 runs great. Plenty of power to pull the hills from Longmont CO at 5k feet in elevation to Estes Park CO at 8k. I pulled most of the passes in 4th gear with only the occasional downshift to 3rd. Never 2nd. I think the J20 has either 3.73's or 4:10's and small tires. It's setup great.

I've rigged up the Transmissions Control Computer (TCC - basically the torque converter lockup) through a 4 wire brake switch and manual toggle switch like this; http://www.rowand.net/Shop/Tech/images/ ... gram01.bmp It's pretty cool to play with the TCC switch. I wanna get rid of the toggle switch and go with either a vacuum switch (to turn off the TCC when the engine is under load as described here http://www.73-87.com/7387garage/drivetrain/lockup.htm) or configure the ECM to do it based upon the MAP sensor.

As for MPG - I dunno. I drove all the way up to Estes Park and back with a little 'wheeling in there and only burned 1/4 tank. I'm pretty sure the Honcho and Waggy with their V8's would have burned much more.

[AwesomeJ10]

I need to get up some pics of the custom fabbed transmission cross member (made of 1.75" DOM tubing and YJ bushings). Also need to get some pics of the radiator brackets, motor mounts and both shifters. I'm running *mostly* stock tranny shifter and mostly stock chevy NP208 shifter.

The main problem I'm having it heat. I'm running an aluminum radiator (with plastic tanks) out of an '80 camaro with the V6. That radiator fits perfect in the stock FSJ location with some custom bracket and utilizes the stock 4.3 hoses. The camaro radiator is larger than the stock S10 radiator and I'm having a hard time keeping it warm enough. I have some carboard covering nearly 100% of the radiator just to keep it at lukewarm temps.

[Snowstorm]

Pretty slick, Blake! Looks like it's gonna be a fun toy...

Glad to see the other half isn't scared to get her hands a little dirty!

What was your Hwy cruising RPM like with the 4.3? In fourth gear, did it still seem to have some decent oomph? I know that motor has decent torque, but I wondered how it would do in a heavier truck...

[AwesomeJ10]

Pretty slick, Blake! Looks like it's gonna be a fun toy...

Glad to see the other half isn't scared to get her hands a little dirty!

What was your Hwy cruising RPM like with the 4.3? In fourth gear, did it still seem to have some decent oomph? I know that motor has decent torque, but I wondered how it would do in a heavier truck...

I don't have a tach, so I dunno the RPM's. I'm having issues getting the motor up to temp (see previous post) so the ECM never really went into closed loop, meaning it wasn't running 100%. But it did seem to have plenty of oomph. I think once I have the TCC all connected in 'fully automatic' mode it will unlock, allowing more torque convertor slippage, essentially creating another 'gear'.

But the initial impressions are that a 4.3 V6 is PLENTY of power for a FSJ. If I need more power, I'll swap in a newer Vortech V6 and pick up another 30-40HP.

I think that if my wife and I were to line up the 401 TBI waggy versus the 4.3 TBI J20, the J20 would win by a nose...

[jaber]

Cool build, thanks for the details...

[Stuka]

I need to get up some pics of the custom fabbed transmission cross member (made of 1.75" DOM tubing and YJ bushings). Also need to get some pics of the radiator brackets, motor mounts and both shifters. I'm running *mostly* stock tranny shifter and mostly stock chevy NP208 shifter.

The main problem I'm having it heat. I'm running an aluminum radiator (with plastic tanks) out of an '80 camaro with the V6. That radiator fits perfect in the stock FSJ location with some custom bracket and utilizes the stock 4.3 hoses. The camaro radiator is larger than the stock S10 radiator and I'm having a hard time keeping it warm enough. I have some carboard covering nearly 100% of the radiator just to keep it at lukewarm temps.

Are you sure the engine has a thermostat in it? If there is one, when its closed it should have no issues getting warm. But if its not there, it will never get warm most likely unless you are really driving it hard.

[AwesomeJ10]

Yep - it has a thermostat. I've even changed it out with another one - same thing.

[nc wagoneer]

Blake, I am really intrigued by this build and am wondering if you have calculated mpgs yet??? My grandfather had this engine in his s10 and it was reliable with plenty of power and would be a good alternate route to a diesel if it got 18 mpg+ thanks, nc wag

[AwesomeJ10]

I've only driven it ~250 miles and that was over the course of the engine swap. So I don't really know the MPG. Only that it 'seems' to be pretty good.

Still having issues with the heater blowing cold air...

[Stuka]

I've only driven it ~250 miles and that was over the course of the engine swap. So I don't really know the MPG. Only that it 'seems' to be pretty good.

Still having issues with the heater blowing cold air...

Is this the one that you replaced the heater core in? Do the hoses going to and from it both get hot? If only one does, it may be plugged. If neither do, then I take it you are still having the strange issue where its over cooling.

[AwesomeJ10]

All the hoses get 'warm' but not 'hot'. I think it has some air in the system...

[sgtpoliteness]

Blake, do you have access to one of the Air Lift cooling system tools? It pulls 20" of vacuum on the system and then allows you to fill it too. I find vehicles with the heater core so high up (FSJs!) can be more of a bugger to bleed.

[AwesomeJ10]

Blake, do you have access to one of the Air Lift cooling system tools? It pulls 20" of vacuum on the system and then allows you to fill it too. I find vehicles with the heater core so high up (FSJs!) can be more of a bugger to bleed.

No, I don't.

I'm thinking about taking it up on a trail this weekend and parking it on a hill, nose pointed up in an effort to bleed it out...

[fulsizjeep]

I like where this is going. Do you have any idea what the running temp is Blake?

[AwesomeJ10]

If I use cardboard to completely cover the front of the radiator, it runs at 195 degrees and the heater works fine. If I leave any of the radiator exposed, it runs around ~140 degrees. So for now I'm using cardboard.

I got a chance to take it out on the interstate and open it up last night. I can DEFINITELY tell it's a V6, not a V8 while going 75 MPH. The tranny shifts down to 3rd, then down to 2nd way to easy. It was hard to hold it at 75 in 4th. I think I need to get a JTR VSS and hook that up so the ECM will run a little better.

My fuel filler hose is leaking badly, so I can't run very much gas and I can't check MPG until I get that hose replaced....

It's a fun little truck though. My buddy came over today for lunch and he was driving his Lexus SC400 (it's sort of a luxury sports car). It was fun trying to keep up with him in the J20 on the way back from the bar

[sgtpoliteness]

It almost sounds like a stuck open thermostat, Blake. Or maybe one that opens at way too low a temp/early.

[Billyj7175]

Nice build. I've always wondered how the 4.3 would do in an FSJ. My ex had one in her Astro and it pulled it loaded with kids and a 6X12 enclosed trailer full of quads with no problem...no tire scorcher by no means, but not a dog either.

I'm interested in what your final mpg numbers are as well...

[mrtazwrench]

All the hoses get 'warm' but not 'hot'. I think it has some air in the system...

I have 2 thoughts on this...

Is it plumbed to the heater as some older GM trucks were with one of the heater hoses to the radiator, those always had heating problems.

Also I had a 360 that would not warm up I found a bad impeller on the water pump.