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My TBI Pathfinder to Z31 MPFI Swap


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#1 Kingman

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Posted 11 September 2010 - 04:06 PM

Well, some background info first. I'm a new member here, my name is James and I'm 18 years young. I've always loved working on anything related to cars, and have a love for Pathfinders. I bought my '88 last August after being rear-ended at 50 from a dead stop in my old '87. I've really enjoyed this truck, but as soon as I changed the oil I knew there was going to be problems soon. It came out as black sludge, I was pretty pissed. The motor lasted me from 177K to 194K, which is a pretty good amount of mileage in less than a year. I spun a rod bearing on the stock motor, and swapped in a motor from an '84 Z31 (300ZX) with only 102K. The bare minimum to get the truck back on the road was to keep the factory TBI set up, which is being a little problematic. I've always wanted to swap in a Z31 intake set up even before I blew the motor, so this worked out perfectly. I found the 300ZX on Craigslist for parts, and the guy said he'd take $100 for the motor. However, since his job schedule kept changing he wasn't able to work on the car to pull the motor out for me, so he said that if I came and yanked it I could have the motor for free.

I've got a TON of wiring to sort through yet, but it'll be easier once the manifold and stuff is on so the placement will all be correct, to help figure out what goes where. At the moment I'm having an issue with the rear hard line coolant hoses hitting the firewall. I can use the other factory lines if I bypass the coolant lines going through the throttle body. I've heard of a lot of people doing this without any problems.... There's also an issue of fuel pump wiring and some wiring for the gauge cluster that I'll need to sort through and remove from the TBI harness as I slowly work it out of the equation. I've done a lot of research on Z31performance.com, mostly for wiring harness diagrams, pin outs, and what other people have removed/changed to make these intakes work with other vehicles. There's going to be an issue with the air intake tubing as well, I noticed the factory Z31 uses some extreme angles that just will not work on a Pathfinder. I'll figure something out, but likely my truck won't be back on the road for a while now.

So far:
Original TBI set up.
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Entire intake removed.
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The Z31 intake prepped to go on.
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I'll keep posting pictures and updates as the project goes on. Any tips and advice from some hybrid project guys would be great!

#2 speeder

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Posted 15 December 2011 - 05:55 AM

I have just finished this swap on my '89. The Z31 intake manifold will not fit the Pathy (firewall interference - I used an upper manifold from a '93 pathfinder with a 1/2" phenolic spacer to get everything to clear the AC compressor), and heater tubes/hoses from the TBI engine have to be used. This was NOT a simple swap with lots of fit issues to deal with.

I'm using a Megasquirt for fuel management, mounted it under the passenger seat in place of the stock ECU, and connected into the stock ECU's connector to pick up the needed signals like fuel pump, TPS, etc.

My engine is a Z31/VG30 ET, and is NA for now (the Z31 turbo interferes with a frame rail) but I will be doing a rear-mount turbo in the near future. I decided to do rear mount with the truck exhaust manifolds because my truck is 4WD and getting manifolds and downpipes to fit a front mount configuration just looks too hard.

I love the old truck but God is it slow. The new engine has a lower compression ratio than the truck motor but bigger cams, so it's about the same as before with my tired 300K engine, which also spun a rod bearing. I'm looking forward to the turbo power.
Rick Bowers
'77 280ZT (Not as fat as I thought) - Awaiting 260ci Twin Turbo Buick Stage II - Finally out of machine shop jail after 2+ years!
'78 280Z (Soon to be for sale)
2002 Lexus IS300 - Turbo 2JZ, 6-speed - daily driven monster.

"Speed costs - How fast do you want to spend?"

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My build thread: http://forums.hybrid...ad.php?t=136300
Old body shown in obsolete website:
Rick's 280ZT AKA: "Porkchop"




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