Astro swap


It ain't easy livin free
Apr 19, 2004
All right, as many of you know I've been working at swapping an LC2 power plant into an Astro van. Progress is slow, partly because I'm a poor college kid and partly because I'm a college kid without much time. I'll post into this thread updates as it happens, so people can see what I'm doing and maybe get some insight into what goes into a swap. I guess if you wanted to call it such this is my swap "blog" if you must.

Here we go, warm up the ol' record machine and put on "Welcome to the Jungle" First off I got the Chilton manuals of both the GN and the Astro van for the harnesses, as well as going to the schematic of the LC2 engine. Some things I would like to point out are these; The harness diagrams weren't always accurate when I went to the pinout, for instance my 88 Astro harness had NO IAT like is indicated in the schematic.
Not all the fuses are the same rating, and some things go through fusible links on the GN ECM that go through the fuse panel on the Astro. Everything has some form of safety device though, and I'll sort through ratings when I get things running.
The connectors for the Astro and the LC2 power plant are the same, so there's not a big issue there and is one of the reasons I'm using the Astro harness. The other is that the engine harness and the body harness are interconnected by a big connector on the passenger side I'd have to pick through otherwise. Here's the pinout:

ECM Pin#-Buick/Astro
A1-Fuel pump relay (coil)/fuel pump relay (coil)
A2-A/C Cutout relay/ A/C cutout
A3-Canister Purge soleonid/Canister purge solenoid
A4-Vac Regulator Valve,ALDL/EGR solenoid
A5-SES light,ALDL/To VP
A6-ECM fuse (key HOT, 10A)/ECM fuse (key HOT, 10A)
A7-TCC clutch,ALDL/ALDL (TCC clutch)
A10-Gauge cluster/Digital ratio adapter
A11-Ignition control module/
B1-/Always hot (15A)
B2-/fuel pump
B3-coil module/DIST
B4-coil module/
B5-coil module/DIST
B8-A/C cutout relay/AC system
B10-neutral/park switch/lift-gate release switch
B12-INJ #5/
C7-Automatic Transmission/Automatic Transmission
C8-Automatic Transmission/
C10-Coolant temp sensor/Coolant temp sensor
C11-MAT sensor/MAP sensor
C12-INJ #6/MAT sensor (NOT IN HARNESS)
C15-INJ #2/
C16-Fusibile Link (A. HOT)/A. HOT (ECM fuse)
D3-WasteGate solenoid/
D5-Coil module/DIST
D7-O2 sensor/O2 sensor
D9-Vacuum regulator valve (EGR diag)/pin D10-D9 jumper (not on my harness)
D10-GND/pin D9-D10 jumper (not on my harness)
D12-X/MAF/TPS/CTS common
D14-INJ #1 (BLK)/fuel Injector (Dk. BLU.)
D15-INJ #3
D16-INJ #4 (BLK/RED)/fuel injector (Dk GRN.)

All right, what this means. If you notice the Astro's TBI system is speed density versus the mass air equipped LC2 power plant. If you notice a good third of the pinout should match up to one degree or another.
What the GN harness doesn't have is a MAP or a dist, so those wires are freed up. Some things like the EGR, air conditioning, WG solenoid (going to use a home built controller) and a few other minor things aren't gonna be used, which will free up one or two additional wires. This will vary a lot depending on what you want to keep in your swap.
With exception to an extra wire going to the ECM, the EDIS wires will even match up in color to the old harness!
The pin D4 in the Astro harness to B4, this will give all but one of the wires going to the EDIS system from the ECM. The last wire will have to be run seperately, as will four injectors and the IAT sensor. There is also the trans sensors as mentioned below
On the engine side there are very few lines that need to have new connectors put on them, just lengthened and shortened as necessary. On this topic I'm soldering my connections, using liquid electrical tape then waiting for it to dry and heat shrink tubing the results.
One issue that I still havn't quite gotten %100 figured out yet is that the GN ECM has a spot for a third gear sensor, and the Astro ECM doesn't. It shouldn't be hard to run a wire for it, depending on if I can put a pressure switch in the tranny or not. It appears the valve body has a spot for the switch, and the 4L60 DOES in fact use one. All I'll have to do is add the wire to the harness in the tranny and add the engine harness.

The top end/valvetrain hasn't been coming along near as much. I've got the intake off a FWD I plan to use for now (hey, I had it it was cheap bitch at me if you like but only if you're willing donate a free GN intake to the cause :D) I'm still short of a cam shaft, but am planning the 204/214 Edelbrock cam (under $140 w/lifters from summit) I also need to port my remaining 8445 head and get another one, then do some work on the valves and get a 3 angle valve job done.

I'm not doing well in the engine department as of now, but I'll be slowly but surely making progress. I've got a set of rods I beam polished, probably will use a FWD crank (for some reason the 86 FWD 3.8 crank I've got has rolled fillets, and they fit the RWD block) a timing cover and that's about it. I've got a block that's .030 and needs to go .040, a set of heads that I accidentally trashed one of by cutting too deep into a valve guide, and a bunch of misc. parts so that doesn't leave me a #*@! of a lot. It'll come together eventually, I'm sure but is fine for mocking things up on. If anyone has an 86-87 3.8 NA long block in the Carbondale Illinois area you'd sell for cheap I'd like to hear from you.
Other engine things of note are the dimensions across the engine's widest point (the head corners) are near identical, even though the 3.8's a "Y" shape while the 4.3L's more a "V" shaped or "U" shaped engine. The main caps are built into the block on the Buick, while they poke out of the Astro's block like an SBC.
Another thing to note is the 3.8L's bellhousing is BOP, the 4.3 is a Chevy bellhousing so a $50 adapter plate is necessary.
As far as mounts go, i'm going to bulid something to where it wil mount into the stock 4.3L motor mounts on the van, and make new engine side mounts for the 3.8L. My current plan for this involves fitting a piece of pipe in the main journals of both, then measuring the up and down difference. The reason this should work is the crank height is the same regardless of what the other block dimensions will be. The distance of the motor mounts front to back is merely determined by how far they are from the bellhousing. I'll probably use 5/16ths steel plate for these, and cut/weld em up myself.

Induction's also coming along slowly, but what I want isn't exactly coming to me easily right now and will probably be finalized later. Right now the plan is to use a Syclone intercooler, and probably sequential turbochargers (a stock GN and a diesel HY-35W) with a radical form propane injection and my own home built controller for both the LPG and the boost it's self.

--GET THE MANUALS FOR THE VEHICLES YOU ARE SWAPPING. If you don't you're going blind
--both the vehicle you're swapping to and the one you're swapping from are handy to have and a spare engine from both. I havn't even bought the astro I'm gonna use, but I can mock up most anything I need in the swap, as i can look at my van and the engines from both the Buick and the Astro.
--Take your time. Don't go at it break neck speed, my goal right now is one small thing a day. If I only make a few cuts on a bracket to make it fit today, that's fine. No use making mistakes that will cost more time and money.
--Just because your "target" and "donor" are X make/model/engine/whatever don't be afraid to use other parts from unrelated vehicles. Whenever I get this engine in an Astro, guess what. It's no longer an Astro van. Lasst I checked they don't make a 3.8L SFI turbo Astro van. Use whatever parts fit.
--Log whatever parts you use in the project (see above) If you use the radiator fan off of a 1995 Honda CRX that you got at the JY, make note of it. You'll have a lot easier time getting parts.

I'll try to keep this updated, may do some pics this weekend.

More to come

Find one with the awd setup they used in sy/ty. It was available in the safari. Hello 15psi street tire launches!
Just an update, havn't gotten about jack or squat done on this lately, but have a thought. I need to make a set of engine mount brackets, I intend on using the configuration as on the 4.3L, and am wondering if this is sound theory. my current plan is to take the stocker 4.3L engine and flip it upside down. The BOP and chevy bellhousings use the same bottom bolts and the pins. I'm gonna use these for the common point, then weld up pieces of steel that will hold the bolt holes for the mounts. When this is on, it should establish where my holes will need to be for the Buick mounts when I construct them, as well as provide some welding support for them. Any thoughts, I wish I had some autocad diagrams or something to show what I'm talking about. Since they make dual patterned transmissions with the aformentioned pins the same, I'm assuming that it'll all line up properly. Am I wrong in making this assumption?
nothing much new to report, just a coupla pics

Intercooler, hooked up to intake

intake it's self, it's a FWD intake but hey the price was right (AKA I had it on the shelf) I'll tell you hot air guys how it performs if I ever get to using it.

This is just a close up of the crank I'm thinking about using. Would you believe this is out of an 86 FWD Park Ave? It looks like a rolled fillet crank to me, how wierd. motor mk-I will just be one I can shrapnel out real quick, to get it fit and running. Then again, we may see what this bad boy can take.

That's all for now, more to come.
Yet more pics, these are the ones of my motor mount jig. Just some junk steel,
but it's only a jig that'll be sent to the scrapyard again.

The big holes are for the transmission pins, the small holes match up with the bolt holes of the transmission. This will be bolted up to the block, and from that the position of my brackets will be gotten.

up close of holes, the pins and the bottom 2 holes on the block are common to both Chevy RWD and BOP bellhousings. Yes, I know there's a third hole there. That's my mulligan in drilling the holes. :)

Big pic of the jig, the tabs off the side are where the mounts will bolt up, I have holes marked but not drilled. The cross is to stiffen it up so that it won't move my holes.
Just wanted to say good luck with the swap. There was a guy around me that had a GN motor swapped in an Astro that used to show up at the local street races around 1996-1998, lined up with him once with my GTA when it was a slow L98 car and boy was I glad I had the spray hooked up that night cause I just barely got him :)

Anyway I always thought it was a cool swap and it looks like your putting alot of work into making it happen on a budget (y)