'83 Monte Carlo V6 to V8 swap

[Monte Cristo]

And if its computer controlled engine you will need some wiring and ecm from donor car if keeping the efi.

Is it just as simple as getting the wiring harness and ECM to match the donor motor? Is the '83 ignition harness plug interchangeable with the '90 ECM, or does it require splicing or other modification to work with the stock ignition? Otherwise, is there a better aftermarket solution to this problem?

 

[malibujustin]

Is it just as simple as getting the wiring harness and ECM to match the donor motor? Is the '83 ignition harness plug interchangeable with the '90 ECM, or does it require splicing or other modification to work with the stock ignition? Otherwise, is there a better aftermarket solution to this problem?

You definitely will want to get the wiring and ecm if you are keeping it computer controlled. May have to do some fuel system changes also...not sure on that one. I also would think the plugs may be different. Look at yours and then compare it to the donor.

 

[Monte Cristo]

OK. I am shopping around for a wiring harness and ECM from a junk yard. Aftermarket solutions are quite pricey for my present needs.

Meanwhile, I have one cylinder head off and soaking to remove the engine crud. I had to take it off for a machinist to drill a broken exhaust manifold bolt out.

 

[Monte Cristo]

OK, so it took a while to do my homework for this transplant.

The fuel delivery system and wiring harness:
Since this system was last stock in '92 or so, I thought that paying for an old wiring harness at a junk yard would be false economy. I was able to find a new wiring harness on Ebay for only $270, but without all of the emissions sensors. The same part was a bit more elsewhere. Speedway's lists at $319.99:
http://www.ebay.com/itm/Speedway-85...Engine-Wiring-Harness-7747-8747-/261842708788
Ron Francis has one with an added controller for much more at $579.95:
http://www.ronfrancis.com/prodinfo.asp?number=TH-60
I went with the cheap one on Ebay. I still need to find an ECM, but I think I can get that at a junk yard OK.

The fuel pump and line:
I still have the old sending unit, but it doesn't allow for adding a fuel pump. Carid.com has a Spectra Premium Fuel Pump and Sender Assembly model SP172A1H as a stock replacement for an '86-88 4.3L Monte (and also an '85 5.0L) at only $82.33: https://www.carid.com/spectra-premium/fuel-tank-sending-unit-mpn-sp172a1h.html
It should fit right in the tank without any modification needed there.

I still need to engineer a new fuel line and return line to the tank and put a filter in it. Steel reinforced nylon hose should work I think, but I have never worked with it before. Do I need to buy the tool to make the connectors, or can I use basic clamps? If I do that, how do I add the fuel filter and where do I put it?

 

[84slow]

I'm in the same boat as you 3.8 to a V8 I'm learning as I go I used transmission out of 86 th350 my drive shaft works perfectly but cross member has to be modified.. going to use f body headers for clearance I think fit better.. and I still used the coloumns shift 3 speed

 

[84slow]

I used Monte 305 frame mounts block mounts from 305tpi fuel just going to run external pump with return wiring I got painless and deleting all emmisions but have to get chip burnt.

 

[Monte Cristo]

I used Monte 305 frame mounts block mounts from 305tpi fuel just going to run external pump with return wiring I got painless and deleting all emissions but have to get chip burnt.

I am trying to keep a stock look to this. These wiring harnesses come with an O2 connection. I am looking at exhaust manifolds. I think I want stock with the O2 sensor port, but don't want the AIR injection. OTOH, the old ram manifolds do look cool. Maybe I can just locate the O2 sensor behind the manifolds?

 

[84slow]

Yea you can drill a o2 bung in there and wire it up.. I want to keep all stock as well biggest thing for me is I didn't want to loose my bench seats and custom a shifter on the floor. And just like the way a tpi looks. I got no performance stuff just headers and a burnt chip I have to do cause I'm not running the smog pump.. no cam or bigger intake runners/throtel body

 

[Monte Cristo]

Yes, the TPI does look mean under the hood. I like it too. I was just looking to get a V8 and took what looked like a good deal. It would have been better in hindsight to get the harness and ECM from one donor, but whatever. I got the V8 now. Now to make it run again for the first time in 21+ years. Then to do some body work. There was just no way I would ever junk this car. I have just too many memories.

Yeah, ditch the smog pump, and customize the exhaust for the most bang for your buck. I am not ready to go with headers just now. I can probably use the truck exhaust manifolds that came with this for now, but they aren't in the best of shape. These look good, cast iron rams horns but they look smooth like a header, so better than stock corvette manifolds:
https://www.auctiva.com/hostedimage...34184421&formats=0,0,0,0,0,0,0,0,0,0&format=0
I could go for those.

You'll have to let me know how burning a chip works for you. I think it creates a phantom input for the vehicle speed sensor (VSS).

 

[Monte Cristo]

So, I just took the cylinder heads to the machine shop for resurfacing. The machinist told me that my casting number 193 is known to crack around the valves. He said when they redesigned this, they took 6 pounds of steel out of the head and it weakened it. So, anyone else considering this swap might want to consider this aspect of the swap if not upgrading the heads right away. For my purposes, I just want this to move the car around the yard for now, so I'm not ready to upgrade.
Edit to note the heads that came with this were not worth resurfacing after inspection. I am looking at heads online.