My 4.3L swap plan and some questions

The players:

-86 MJ; 180k+ mile 2.8l, no wiring harness or dash (previous owner removed them after a fire in the harness and then never put them back since it ran good enough for farm work, I've since added wires to the lights and what-not to make the truck street worthy), it is 4wd but that feature has never been used in the 6 years I've owned her and I hardly need it now that I have the 88 around. I originally bought her to haul rocks and dirt around (metric tonne).

-91 S-10; A truck that my uncle owns, mild hit in the front drivers side, ~100k mile 4.3l, 2wd auto, been sitting for the last couple years, I can get it practically free

What I want:
I'd like to make the 86 driveable again. The carbed 2.8 is tempermental at best and not exactly something you'd want to commute with. I'd like to swap the 4.3l/700r4 and the entire wire harness (maybe even the dash too) into the MJ. This won't happen for a couple months at the earliest so I have plenty of time to think about it and take measurements and what-not.

The questions and my thoughts:

Finding an online write-up with pictures would be sweet, but maybe that's shooting a bit too high. The most detailed lists I've found so far are the AdvanceAdapter info and YellaHeep's comments here: http://www.naxja.org/forum/showthread.php?p=206168#post206168


What has everyone done with the exhaust manifolds? I remember hearing somewhere that only the drivers side will need replacement? AA recommends ones from a 78 Malibu classic but I've read that an Astro manifold works too. The AA headers are out of the question for cost reasons.

What about the radiator? I know that a brand new stock-size one is insufficient for offroading, but what about for highway use? Or do I have that backwards and the highway use is worse?

What about connecting the S-10 steering pump to the MJ box?

I refuse to pay anyone $170 for motor mounts so I'll be fabbing those up. The AA motor mounts drop the engine too low anyway. The MJ won't be getting a lift anytime soon and AA requires 3 inches to clear the suspension. I'm much more willing to modify the hood to clear the top of the engine if it is indeed that close. This MJ is far, FAR from being a beauty queen so no worries there. What exactly are the clearance issues with the firewall? Why is it that the AA mounts are so low? Is it simply to allow use of the mechanical fan? Couldn't the engine be pushed forward a bit? If it comes down to it, firewall mods are ok with me if it helps out with the rest of the build.

Do you think I could use the S-10's steering column? Wishful thinking? That would simplify my wiring immensely.

I plan on using an electric fan, so I won't have to mess with the mechanical one at all. I won't have to build a shroud, and don't have to worry about fan clearance with the rad or hood.

I was thinking of just adding an inline fuel pump.

Oh, and the tranny mount/crossmember, rear shaft, and the rest of the exhaust are fairly straight forward. I'd like to just copy what I did to my 88.

This is a budget build for sure. Normally swapping in the 4.3l is reasonably expensive, but since I'm using all the S-10 wiring, keeping it 2wd,, going with the auto and fabbing my own mounts, I hope to keep everything under control. Heck, with a bit of ingenuity, I might even get A/C! It's not required, but both trucks had A/C so it should be possible with some effort.

Please don't bother with recommending other possible engine swaps (like the 3.4, which I know all about), this is the only one being considered because the S-10 is free and complete. If the S-10 doesn't live up to my expectations (I'm going over there tomorrow to try and fire it up), the MJ with remain as-is and I'll just go ahead with commuting in the minivan (gag). Maybe someday I'll continue the swap and make it 4x4 again, but for the time being I'd like to give the ol' girl a new lease on life.
Jeep on!
--Pete

Well, I got the S-10 fired up. Runs good but smokes a bit. I ran out of daylight so I'll be going back in a few days to pop the valve covers and see if the valve seals are good or not. If the oil is seeping by the rings, this plan is being abandoned and filed away under "almost".

I have another question for those of you who used the 700r4, how did you do the shifter? This S-10 has a column shift. Can I put in a floor shifter? The MJ is a stick so I was thinking it'd be easier to install the 700r4 with the floor shifter.
Jeep on!
--Pete

Not sure about the s10 shifter stuff but, an 86 MJ I parted out a few years ago was an auto on the column. You might be able to use the floor shifter stuff from an XJ with a little creativity. As far a the smoking deal prolly just needs valve seals. A visual inspection prolly won't tell you much. Think I would prolly use xj interior stuff like dash and such with a console and shifter for the auto. Just make the wiring for engine work somehow.
You would a wiring diagrams from both vehicles. Little work in tracing various wires and it would work. Just my .02

There are a boatload of aftermarket shifters out there for the THM700R4 - I'd start with Hurst and B&M - and work outwards from there. (Lokar probably does a few as well.)

The THM700R4 isn't a bad box, but if it's been in service for a while, you might want to go ahead and overhaul it - the clutches need a little help. The valve body should be upgradable to manual shift, or change the shift points around if you'd like.

If the engine has been sitting for a while, it's a sure bet that the valve guide seals have shrunk and are leaking. Change them, it will likely go away.

If the 4.3 is injected, you might want to grab a later fuel tank with the in-tank pump, and use that. The inline pumps are usually set for a retrofit to carburetted vehicles. See if the regulator is integral to the fuel rail or the pump, and take necessary measures to get it into the MJ.

The oil rings probably aren't leaking - they tend to hold up as long as there's compression available (even though they aren't compression rings. They're under less tension than the compression rings, and only fail if the oil supply fails.)

That's all I can think of for the moment...

5-90

Pete,

This is the exact same swap I had in my first rig, an '84 XJ with a '91 S-10 engine.

First, do what you can to keep the fuel injection - you'll be much happier with it's performance than if you try to swap to a carb. Also, the oil smoke you see at start up is most likely cracked oil seals on the valves. I had a '91 S-10 (not the donor vehicle) bought it new and at 19K miles, had the seals replaced under warranty - dealer said it's a common problem and the replacements are of a different rubber compound.

You're right about the AA engine mounts being kinda low, but that's for hood and trans tunnel clearances. I imagine the 700R4 will be VERY tight to the firewall with the AA mounts, so if you make your own, keep that in mind. My swap used the S-10 5speed and that bell housing was awfully close as well.

I hadn't heard about the Malibu manifolds, but the Astro ones are best. I used the S-10 ones and just hammered a large dimple in the pass. side frame rail for clearance. Worked out just fine.

Radiator: The S-10 uses a funky 5/8ths heater hose bypass from the water neck to the radiator in addition to the usual radiator hoses. I used a 3 core XJ radiator and had a radiator shop add a connection to the upper tank for the add'l hose. Worked out fine and didn't have to make any funky radiator mounts for a custom radiator. A standard radiator probably won't be adequate for the 4.3 - especially if using it to haul loads.

Fuel: You'll be best to source an MJ fuel tank from a later model for the electric fuel pump (if you keep the injection system). I got a tank from a '94 XJ when I did mine and that worked great. You may be able to use an aftermarket elect. pump, but you'll need to figure out the pressure and volume needs of the injection system to make that work.

Shifter: I'd be curious to see if the S-10 column might swap into the MJ since both are GM columns. You might be able to fab up the linkage to work, but if not, then a floor shifter with a cable will work fine.

Another thought...... and don't hate me for it: If the S-10 is a light hit in the front, and you want a truck for commuting and hauling, why not just sell the MJ and put that money into repairing the S-10? Seems like a lot less headache with fabbing parts and wiring. I understand the desire to get a rare MJ back onto the road, but again, if it's just for hauling and commuting, I'd stick with the S-10.

I sent ya my write-up as well.

HTH.
Troy

Thanks for the pointers guys!

I called it a "light hit" because the engine is unscathed. The frame and cab are tweaked beyond repair (at least beyond my abilities or funds). Otherwise the truck would be repaired for my cousin to drive so he isn't stuck with the Escort when he get's his license next year.

I'm hoping that after I remove the mechanical fan I'll have room to scoot the assembly forward to help alleviate the tunnel issues. It's hard to say for sure though, and I'm still hoping to find someone that has done the swap with the 700r4.

If you got the S-10 manifolds to work, then I'll definitely try those first.

My biggest concern at this point is the radiator mess. Did you use the stock 84-86 mounts?

What did you do to adapt the power steering?

And I'll definitely be using the TBI. There's so little to it, why would anyone not?

Jeep on!
--Pete

Pete M said:

Thanks for the pointers guys!

I'm hoping that after I remove the mechanical fan I'll have room to scoot the assembly forward to help alleviate the tunnel issues. It's hard to say for sure though, and I'm still hoping to find someone that has done the swap with the 700r4.

If you got the S-10 manifolds to work, then I'll definitely try those first.

My biggest concern at this point is the radiator mess. Did you use the stock 84-86 mounts?

What did you do to adapt the power steering?

And I'll definitely be using the TBI. There's so little to it, why would anyone not?

Jeep on!
--Pete

Click to expand...

I did this swap on my '87. It's not bad. Originally my truck had been a 4-banger so the radiator set-up was probably very similar to yours. I used the AA mounts and clearance was a little tight with the rad. I was running a puller fan on the back of the radiator. I eventually swapped in a 3-core 4.0 radiator that left plenty of room. You could look into the universal aluminum radiators from Howe and Griffin in SUmmit or Jeg's. You should be able to find one that's close in size to the mounts in your MJ plus you can get them with the inlet/outlet on the correct side for a GM application.

I don't think you'll have a lot of clearance issues with the trans tunnel. I had plenty of room using the AA mounts and I was using a 2WD 700-R4. The main issue with clearance was that the motor mounts hit the UCA mounts on the axle. With fabbing your own, you could keep the engine placement low but still build in the clearance for the UCA mounts. Plus you might be able to build in enough clearance for the S-10 manifolds.

I just used the GM pump and hooked it the Jeep power steering box. Everything bolted up and I had no problems with pressure. Also, I used a carb on mine but I really wish I had gone with EFI. While you have the 4.3 out, pull the heads and port the chambers a little to give you some extra juice. If you look to build it down the road, Crane & Comp Cams make EFI-friendly roller cam grinds for the 4.3. Just a couple of ideas.

Good luck and let me know if you need any more info. I'll give you as much as I can.

Brent

Pictures! Lots and lots of pictures!
Jeep on!
--Pete

I'll have to check in my scrapbooks. Most of the pics I have were taken with a regular camera because I did the swap during winter 1995. Unfortunately, I don't have that MJ anymore so I can't get any current pics. I can try to help with as much as I remember, though.

D'oh! Well, keep me in the loop if you come across them. :laugh3:
Jeep on!
--Pete

Any updates, Pete?

Only that the compression test results were good and now the project hinges solely on convincing my father that he needs to fund it and turn over his garage for ANOTHER one of my projects. The S-10 isn't going anywhere fast so my attention has been focused on getting my Dakota R/T prepped for sale and the 88 ready for wheeling in 2 weeks. It's a local gig, just some easy wheelin' and I'm towing the truck there, but I still need to flush out the remnents of the old water pump from the system and figure out what the heck that thunk is when I turn a corner hard. Last time it was the trackbar moving but this time there's no evidence of that.
Jeep on!
--Pete

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