91 Caprice Engine Swap to LT1

I've got a 91 Caprice with the civilian police package (bigger tires, oil cooler, beefed up suspension, 3.08 gears, etc) and I want to replace the tired L03 with an LT1. I've seen a couple of cars around that have done it, one was a 91 and the other a 92. My questions are as follows:

1. Will the stock engine mounts on the frame work for the LT1? One of the 91 Caprice owners that swapped the L03 for the LT1 had a series of pictures showing how he had to move the engine mounts. I'm not sure if that's because of something else he did, or because the LT1 bolts in differently than the L03.

2. I know a guy with a 94 Roadmaster who only wants $500 for it. Is it true that all 94-96 Roadmasters came with the LT1? Or was it just the wagons? (This is the sedan).

3. What kind of exhaust should I use? I've already decided on single-pipe, just because of the difficulties involved with modifying the 91's frame to take duals. But should it be 2.5" or 3"? Will the 3" be too big? (i.e. not enough back-pressure for proper operation?)

4. The transmission I have currently is the 4L60, whereas the LT1 (as far as I know) always used the 4L60E. Is this a problem? Will it work with the regular 4L60? Is there any advantage to the 4L60E?

5. My transmission has 250,000 km on it, and the Roadmaster's has 300,000 on it. Would it be better to get a 4L80 transmission and put it in instead? I'm assuming that the transmission won't last long, both due to the high-mileage and my lead-foot. I've read in places that the 4L60 is sufficient for the LT1 with stock power-output, but when you start modifying it the power can be too much for it.

6. What modifications need to be done to the stock fuel system (besides replacing the standard fuel pump with one that can meet the LT1's pressure requirements)?

7. My budget is approximately $2000 for parts for the rebuild, and about $1000 for everything else (machining, unforseen costs, etc.). Is there a rebuild kit I can buy that will fit the budget, or should I just get individual parts?

8. Anything else you think I should know?

Thanks a lot.

I've got a 91 Caprice with the civilian police package (bigger tires, oil cooler, beefed up suspension, 3.08 gears, etc) and I want to replace the tired L03 with an LT1. I've seen a couple of cars around that have done it, one was a 91 and the other a 92. My questions are as follows:

1. Will the stock engine mounts on the frame work for the LT1? One of the 91 Caprice owners that swapped the L03 for the LT1 had a series of pictures showing how he had to move the engine mounts. I'm not sure if that's because of something else he did, or because the LT1 bolts in differently than the L03. if you delete the AC I believe your mounts will work, the LT1 uses a little different bolt hole in the block to make room for the AC
2. I know a guy with a 94 Roadmaster who only wants $500 for it. Is it true that all 94-96 Roadmasters came with the LT1? Or was it just the wagons? (This is the sedan). all 94-6 roadies sedan or wagon

3. What kind of exhaust should I use? I've already decided on single-pipe, just because of the difficulties involved with modifying the 91's frame to take duals. But should it be 2.5" or 3"? Will the 3" be too big? (i.e. not enough back-pressure for proper operation?) 2.5" is plenty for all but truely wild motors
4. The transmission I have currently is the 4L60, whereas the LT1 (as far as I know) always used the 4L60E. Is this a problem? Will it work with the regular 4L60? Is there any advantage to the 4L60E? can work with either, personally I like the "E" tranny due to ease of tuning
5. My transmission has 250,000 km on it, and the Roadmaster's has 300,000 on it. Would it be better to get a 4L80 transmission and put it in instead? I'm assuming that the transmission won't last long, both due to the high-mileage and my lead-foot. I've read in places that the 4L60 is sufficient for the LT1 with stock power-output, but when you start modifying it the power can be too much for it. forget the 4L80, the 4L60E gets a bad rap because of bad builders, my car makes conservatively over 200hp more than a stock LT1, tranny is 4 years old all of that with a modified engine year and a half with current power
6. What modifications need to be done to the stock fuel system (besides replacing the standard fuel pump with one that can meet the LT1's pressure requirements)? fittings to hook to the fuel rail

7. My budget is approximately $2000 for parts for the rebuild, and about $1000 for everything else (machining, unforseen costs, etc.). Is there a rebuild kit I can buy that will fit the budget, or should I just get individual parts? what are you looking to rebuild? GM did a better job with the motor than any budget machine shop can do, consider bearings, valvesprings but don't bore it unless it needs it which is unlikely
8. Anything else you think I should know?
you would be better off just getting an LT1 car, lot of wiring involved. Unless there is some specific reason you want to use the 91
Thanks a lot.


When I swapped out my original L99 for an LT1 a lot of guys told me to just buy an LT1 car, BUT for me it was a drop in swap because the L99 is exactly the same far as bolts and sensors and all. For you though this is a big project, nowhere near dropin. The skirts are probably a problem too if you want to run performance rubber under the car.
you are talking $500 for motor, $2000 for "rebuild, and $1000 for other stuff, you can find a LT1 car complete and daily drivable for that amount of money.

Thanks for the detailed reply, lots of helpful info in there. First of all, check this out: http://www.capriceshop.com/

17x8 wheels are no problem with skirts, and I love the way the skirts look. The other thing is, the body on my car is near-perfect. Theres a rust spot on the trunk lid and a few small ones here and there, but I'm fixing them all myself. To find an LT1 car up here in Canada is not easy, and finding one thats in good shape like my 91 is is near impossible. I'm prepared to do the work cause I love my car, and for me it makes sense.

Now when you say "Don't get it bored unless it needs it," you're talking about the cylinders right? I work on cars, but this would be my first rebuild, so lots of new stuff for me. I'm familiar with all the external components, but I've never actually taken an engine apart. But don't you think that with 300,000 km on the engine, it would be a good idea to get the cylinders bored on put in oversize pistons? Or is that unnecessary?

Also, I figured I could transplant the entire wiring setup from the roadmaster to my Caprice, which would simplify things a lot.

Thanks again for the reply.

On the engine even at that milage you are unlikely to find signifigant cylinder bore wear, the injection keeps even cold start air fuel ratios good, on older stuff carbs often dumped too much fuel which washes oil off the cylinders and that is what caused a lot of wear.
If you rebuild it and have it bored make sure you use a good shop, probably pay a little more but a cheap shop will likely bore the cylinders and have them endup less round than original and rings don't seal well like that.

I would look at using as much of the Roady wiring as possible.

I run Impala wheels which are 8.5" wide and have considered going wider, my drag tires are 27x11.50 on 15x10 rims and still need to work on the suspension to make traction better. Mine is far far from stock though and sometimes I forget that with a stock engine you don't need so much rubber.

I know what you are saying about finding a good body, my caprice is not too bad definetely rust but no holes, my wagon is bad, the wind noise of it is louder than the engine/exhaust of my Caprice while driving.