swapping 4.3 to a 5.7 last minute questions

I would use the ECM and wiring from the 5.7 with this swap and the 5.7 motor mounts too.

I measured the motor mounts and you're right. Got to use the ones from the 5.7. I got the computers out and the plugs are completely different. So are the chips. So I got the wiring harness out of the Caprice and it's completely different than the one from the truck.

So what now? How do I use the harness out of the Caprice on the C1500? Are the other things that are hooked up besides the computer at the dash end important to make it run? There are different plugs that go to different things between the two . Should I go through the harness and just change the wires that go to the computer and use the ones from the truck?

Can I buy a different chip for the truck's computer and just use the original harness?

The problem is that you have a different engines and different emissions classes too (car vs truck) so the sensors and ECM is different. What connections are you lacking or are different on the engine harness in your truck currently? You might beable to transpalant some of the sensors but I need to know more here.

I am going to throw another monkey wrench or two into the mix. Truck has clutch, car had automatic. Where did he get the flywheel from? and in this same line up, the prom for a stick is different than for an auto isn't it?

Just guessing here, but it seems the computer from a V-8 truck with manual shift that year along with the distributor might be needed. The rest of the harness should be the same, as this is the throttle body set up.

Oh and the "pads" on the cross member that the motor mounts bolt too are going to have to be moved forward I believe.

Whitelightning

Oh this is a good one. The V6 is balanced differently I believe so it may take a different flyweel (no 100% sure on this but it bears verification.)

Actully the 4.3 and 5.7 is the same engine just missing 2 cylinders is all ,and this is why these conversions are the easiest to do since they basically almost bolt in ,just need a a new set of motor mounts or get the ones out of the caprice which is doable ,but I would suggest just get a new set just to be safer,and you may need a new radiator for the v-8 but you can see if the caprice will work there too . Now for the computer the stock one is set up for a 6 cylinder engine and that is different from the 8 cylinder one so it is pretty much useless for using it on the 8 ,but since you still have the caprices computer yet I suggest you use that one ,it having an auto originally may be a lil bit tough but not impossible ,I do believe that GM at that time used the same computer for the same size engines whether they were in a truck or a car they were just programmed differently and they also actually had a seperate computer body for the tranny and it ran off the engine Rpm's, so all you have to do is get the covers for the plugs to the tranny ,and just hook everything up as they were on the car ,now you may have some trouble with hooking the O2 sensors up depending if they are the same or not if the same hook it up if not and the plugs don't match just get couple nuts that have the correct thread and get them welded on your exhaust in the same location as stock ,and if your going to buy a new exhaust ,pay the money and get a stainless exhaust you wont regret it . now for the caprice when you sell it let them take the 4.3 and make sure the the computer is with it less hassle or you can take the car and donate it to your local vo-tech automotive class and write it off your taxes next year and they will appreciate to get a free car. good luck

And don't forget the front springs. Or maybe you can re-arc the rears to lower them too.

Well the engine is in. I got a chip #16198069 for the computer and used the original wiring harness and all. I have to lengthen the plug for the oil pressure gauge switch (which I broke so I have to buy a new one- $26) and I need to buy a new O2 sensor because someone stepped on it while it was out of the truck and broke it in half. (another $50). And I broke the the fuel return line trying to bend it to fit. So I gotta get a connector to fix that.

The motor mounts didn't line up and I had a hell of a time with those. Ended up mounting them to the engine, dropping the engine in place, then welding the motor mounts in place. I wasn't going to try removing the engine again just to drill new holes for the mounts. That tranny was a royal bitch to line up and get connected to the engine. I ended up getting it real close and just using the bolts to pull it the rest of the way together. Not going to do that again.

The exhaust did not line up. The pipes going to the exhaust manifolds were too short. I tried using the Y pipe from the Caprice, but the clutch slave cylinder is in the way. So I have to weld the two together to make something work.

And the idiot who I paid to put a replacement 4.3 in it (he put a junkyard engine in that was DOA.) didn't put the clutch hose out of the way and it burned a hole in it. So I have to either find a coupler or buy a new hose. Since those things are around $100 I will do my best to find a coupler that works.

And there are plugs that I don't know what they go to now. I can't find anything to plug them into. There is one that went to the EGR valve, but the one in the 5.7 doesn't have anything electrical coming out of it. So I don't know what to do with that. And there are a couple more that have me flummoxed. But I figure if I can get to run, however badly. I can take it a qualified mechanic who can hook everything up the way it needs to be.

So I got everything hooked up as best as I could, poured some gas into the throttle body, put the chip in, plugged it all up, put a battery in, and tried to start it. FIRST CRANK it went VROOOOOMM!!!!! it ran fine until the gas was gone. I have never done a project this major before. I can't believe it actually started.

It's supposed to rain all day tomorrrow so I can't get under there and do anything else for at least a day. When the weather allows I will finish the rest of the stuff. Hopefully I will be able to post that it is on the road in a few days. It's looking good so far.

Anyone got any links to a site that might have a diagram of where all those plugs go to and what I can and cannot leave unhooked?

You are going to be in a bad way if the heat from welding breaks down the rubber and its bond to the mounts.

Yeah, when/if I have to change the mounts it will not be easy at all. I know that. But I am hoping that I can get a new vehicle before they do finally break down and fall apart. My truck has 218,000 miles on it. The engine I put in it has 189,000 miles on it. It's not going to last me forever. It's already pretty much worn out. But I will have around $300 invested in getting it on the road versus not being able to buy a new vehicle right now. It was kinda the worst possible time for me to total my other truck. I have to have a truck to make money to be able to buy another truck. So there's the catch 22.

It's just a temporary thing to get me through until about May when I will have enough cash to just go buy a better one. So it may work that long at least if I take it easy with it. Going to be hard to take it easy with that 5.7 in there. It was pretty quick before, I can't imagine what it will be like with that engine. I had an old 1975 shortbed with a 350 2barrel carb and a 3 speed in the column. If it's anything like that it's going to be something fun to drive.