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'79 510 Wagon Heart Transplant


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Hello all,

     Over the past 8 months, or so, I've been doing an eng/tranny swap into my '79 510 Wagon. It had a 5 speed/L20 combo, originally. A friend of mine, @dukerollo, took the eng/tranny out to swap into his 210 and put the A15/automatic into the wagon. He already lowered the wagon and did the trans tunnel work. I ended up buying the wagon from him, drove it for about a year or so, then we started toying around the idea of swapping another motor in. The A15 ran pretty strong, but was a little small for the wagon. Anyways, he ended up finding a '81 Wagon out in Oklahoma (we're in Arkansas). It had a "running" Z20 and 5-spd, plus some good body panels that I needed. With some effort, we managed to make the trip up there, bought the car (running and driving) for $400 and trailered it back. I was pleased to find that the motor ran decently, the clutch felt good and that it had a dogleg tranny in it! Now that I have the car running and driving smoothly, I just wanted to post some of the problems/qwerks that I had to figure out with the process of the swap.


- First, to do the swap, we took the motor out of the donor. We took it out from the bottom, taking the subframe and tranny with it. The clutch, as I said, felt fine when driving it onto the trailer, so I elected to leave the eng/tranny bolted together. Next, we took the motor out of the '79 the same way. Leaving it up in the air (and after replacing trans seals/motor mounts with it out of the car) we slid the z20 under the '79 and bolted 'er in, subframe and all. Of course, this involved taking the steering arms/sway bars/drivetrain/exhaust components out (or at least out of the way). I also took the valve cover off and looked at the condition of the head. It was all as it should be, nice and clean. So, I checked torque on the head bolts and put the cover back on.


That was the easy part.


- Once we got the motor in, I had to swap over the clutch components. I got the master, slave and clutch line installed. I filled it up with DOT 3 fluid, tried to bleed the system, only to find out that the master was bad and wouldn't pump at all. If you've never messed with the bottom nut on these things, you won't know the frustration. I got that master replaced, along with the slave.. it was like $15, so why not... and boom, back in business.


- I had a Weber 32/36 from the A15 and wanted to install it on this motor. Once you get the right adapter, installing it was pretty easy. The throttle cable from the '79 was way short, now that the carb is on the other side of the motor. I had to use the donor's cable, zip-tying it along the firewall because it was too long. I also had to swap the cable's end, the stock one wouldn't work with the Weber.


- Next, I wanted to get rid of all the emissions crap (the z20 was a California 8-plug head). I bought some exhaust manifold plugs, to get rid of the EGR piping. Getting the tube's nut to come out was a headache in itself. Removed the EGR, plated it off, then removed/plugged everything but the vacuum line to the valve cover and dizzy advance. The exhaust from the donor is all rotten past the trans mount point, so it wasn't usable.


- After the fuel and air were all hooked up, it was time to take a look at spark. Dear lord... this is where many... many headaches happened. After many trial and error hook ups, many tests with a voltmeter and many views of wiring diagrams, I finally got switched power all the way to the coil. I say switched power (black w/white wire), because that's mainly the wire I was chasing. That, and making sure the engine was grounded properly, was a chore. The starter was bad, so that was the first thing to swap out. Anyways, for all of the events after that, you can read this forum:


To see the struggles I went through getting the thing to spark. I ended up getting the hot-spark dizzy, for an L20, and a 3.0 Ohm coil. The z20 had a hitachi 4-plug dizzy on it, from a 720, and only ran the 8-plug head off of the 4 plugs nearest the exhaust manifold. Anyways, the L20 and Z20 have the same dizzy attachment, so install was easy. I have the motor set to about 12-15 ish degrees, and it's happy. Anyways, it was a chore to figure out which wires went where because of all the extra emissions/A/C wires included. I highly suggest getting a Haynes manual. I did, but after all of this process, and it had diagrams for both years of my cars.


- I got oil in the motor, and put GL-5 in the tranny. Whoops. After reading some other threads, I came to realize these older trannys need GL-4 that is yellow metal safe. I didn't run the car for more than a few days with GL-5, so I don't think it did any damage. GL-4 is surprisingly hard to find around here... so I went with Royal Purple's 75w90, which claims to be used for GL-4 and 5 purposes and claims to be yellow metal safe.


That was pretty much it, mechanically. Interior wise, I had to swap the speedo cable (the bung is on the driver side of the tranny for the 5 spd, so automatic's was too long). I swapped out the pedal box. I tried to swap gauge clusters too, the donor had a "sport" gauge cluster. The round bundle of wires that go into that ring of pins (that only slides into the cluster one way) did not work right. It connected fine, but the controls all did different things. One day, I'll go through and actually connect it all. So for now, I left the stock cluster. I also put some brass shift bushings in. This made a HUGE difference in shifter feel, the old plastic ones were crap.


Exterior wise, the donor had a good hood, and front pass fender that I needed. Not to mention a good front valance. All of these fit right on the '79, even though the '81 had square headlights. Almost every other panel on the donor has rust.


I will say that Rock Auto, along with Ebay, have claimed a lot of my money. But hey, it's WAY more fun to drive now. Even with all the parts I had to buy, I don't think I've spent much more than $1K for everthing. The hot-spark dizzy has been working as advertised, although I do plan on getting the Hitachi rebuilt. I'm also pretty glad I took that gamble of not replacing the clutch with the motor/tranny out of the car. It feels/works great. I'm glad I took the gamble on the whole swap, really.


Thanks again to all of the replies to help me get it running.

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The dual plug distributor is a better setup and already higher EI output than the 3 ohm coil hot spark, surprised you took this out. You really should re-think this move.


GL-5 is bad over the long haul. Won't hurt it for short time use if ever on the road and needing to be topped up. Royal Purple is synthetic? Keep an eye on the tail shaft seal for 'wetness' as synthetic can 'slip' past seals. I suspect this synthetic is the same base stock as the GM Delco fluid I'm using, just a different color added. Marvelous shifting quality compared to the original 80w90 gear oil it came with.


The later Z20's dogleg has very slightly different internal 1st and 2nd gear ratios than the L series one.

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@datzenmike It came with a 4 plug (single coil) dizzy. I couldn’t find a 8 plug (dual coil) one, or I would’ve run that. But yeah, I have observed a LITTLE wetness on the driveshaft from the output shaft seal. It’s def tranny fluid... because purple... What fluid would you recommend exactly? I just used the royal purple to get the car on the road again. 


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'80 should be single and '81 dual plug heads except California which were all dual plug. The single plug distributor is, or should be, an EI matchbox identical to the L series. Look and see if it has the E-12-80 module on the side. If points try to find one then you can run the lower resistance coil for higher output.  


I think you said you changed the seals but if not try replacing the rear driveshaft seal. The driveshaft must come out and it's tight in there but a new one should fix this. They are only <$5.... just a pain to get at with the transmission in. Be sure to grease the seal or the transmission spline so it doesn't start up dry. If you did change it you could try another and if no luck change to a non synthetic GL-4.  

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It is the Hitachi E12-80. It’s not stock for sure. The PO put it in, running only one side of the plugs. If I find an 8 plug one, I’ll snag it.


I replaced the seal when everything was out, carefully, and oiled everything. When I put the GL-5 in, it leaked the same way, so I thought I over filled it. 


I drained the GL-5 out and added the Royal Purple in a little more carefully, and it still does it, just not as much.


whats a good non-synth GL-4??


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You would need two coils with impedance below 1 ohm for it to be worthwhile.


No more power, a bit more efficient and lower emissions. It would then run with about 30 to 50 timing rather than 12 and be more ping resistant. Dual plugs shorten the burn time so you must light the fire later. The biggest advantage is the high output EI spark.  

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Awesome, thank you! I ended up finding a dual plug dizzy, refurbished already, for $120. But if there’s no power difference, I don’t think it’d be worth the trouble of swapping it. I’d have to buy 2 new coils, and wire it all together.


The car runs fine right now, I don’t wanna take apart something that works unless it’s definitely worth it.

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Agree. Keep eyes open for free stuff. I collect all kinds of stuff and some I use later. Got a set of '84 Maxima struts and brakes years before I had any possible use for them while owning a truck. You never know what you'll find abandoned. Z24 distributors from the 720 trucks should work also, does not have to be from an '81 A10..

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  • 7 months later...

Sorry to bring up an old thread, go to Napa Auto Parts (Cabot carries it) for true GL4 trans fluid made by Sta-lube, or jump on Amazon or Summit racing and order a few bottles of the good stuff, Redline MT90.

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