I'm not quite sure where to start. There are a lot of things that have to be changed or converted. I guess the first place to start, would be to get your hands on an LT1. If you've already got one, well then you're ahead of most people. If you're wondering about prices, well, I've seen them go for as low as $ 800 with both computer and wiring harness (the set-up that I bought!!), and as high as $ 2000, stock, with computer and wiring harness. So I guess it all depends on the knowledge of the seller. Low price most likely means uneducated seller and a high price is probably going to be asked by a knowledgeable seller. But as time goes on, prices have/will decrease, as age becomes a factor.
First we'll talk clearance. One thing that is for sure is that if you're planning on installing an F-Body LT1 with ALL of its accessories, you're going to have to move and modify your existing passenger side motor mount/frame. If you want to go with the Corvette LT1 and accessories, you won't have to move the passenger mount, but instead will have to change the exhaust slightly. The mount will have to be moved rearward a little, to allow for the A/C compressor and lines to fit without interfering with the frame in any way. Another thing that has to be changed, only if you choose Vette LT1, is the exhaust manifolds. The Vette ones dump in the center and on 3rd Gens. the frame is in the way, so Camaro/Firebird manifolds are required. If you are thinking of installing headers I recommend getting SLPs 1 3/4" ones. They're top notch, quality-wise and they work perfectly, regarding clearance with the LT1's D-port heads, etc.
Speaking of exhaust, the flanges on the LT1 manifolds are a 3-hole configuration, and the ones on any other 3rd Gen. are a 2-hole design. So, that means that the flanges on your y-pipe, which by the way lines up VERY close, have to be changed. The passenger side on your stock y-pipe comes up at a little too much of an angle to use safely. So I got a hold of a 4th Gen. y-pipe and did a little surgery on it. I cut it up and bolted it on to the manifolds. I then brought it to an exhaust shop and had them custom make me a pipe, using my stock one and the flanges off of the 4th Gen. pipe. The stock 3rd Gen. y-pipe is actually larger than the 4th Gen's. are. It is not a possibility to use the 4th Gen. one, because the 4th Gen. dumps out for the cat, right where the frame runs. So it has to be cut and pasted, so to speak. But running a header like SLP's, allows you to ignore using a 4th Gen. y-pipe, as SLP includes a y-pipe with their headers.
To get the engine to fit in the car, when using F-Body accessories and A/C, the frame on the passenger side has to be pounded slightly, not very much, but some. It is just a small corner of it, on the passenger side, right next to the A/C compressor. The engine will not fit if this is not done. The A/C compressor is in the way, it hits the frame, so unless you don't want/need it (in which case, you would need a 1LE A/C Delete Pulley), the frame has to be bent. The first time I did the swap, I thought I wanted A/C. But now that I've done it again and have thought about the weight advantages of not having it, I have chosen to get rid of it and run the 1LE delete pulley. Once the engine is in the car, you'll notice that it sits considerably lower than the stock TPI set up does.
The wiring harness is another topic. If you plan on using any other transmission (electronically controlled), besides the 4L60E (computer controlled), you'll have to get another wiring harness. The harness that I chose is from TPIS. I purchased their "Street Rod Harness". This harness allows you to use your stock 700R4 with the LT1. It also allows you to get rid of the emissions equipment if you choose (Air Pump, etc.). Howell Wiring makes TPIS's harness. They're very well fabricated. Each connector is the same color as stock, and has a little tag on it telling what it is and where it goes. All of the wires are covered in a mesh like covering that is more flexible than the stock plastic tubing, making it very easy to work with. Also, once you get a hold of an engine with computer, you'll have to have the Vehicle Anti-Theft System removed from the computer. The V.A.T.S. prevent the easy install of a possibly stolen computer/engine combo. One thing that you'll need, that I didn't know about when I tried installing the harness, is that you'll need the connector and wire extension for the DTIS (Distributor to just about the passenger side manifold), sorry I forgot what exactly D.T.I.S. stands for. I just ended up taking it off the factory harness, I thought the harness was missing something, but I was wrong. Anyway...
Among the list of things that need to be converted, is the A/C, for one, if you want it. As I said earlier, I chose to keep it the first time, but have since decided that it's not something that I have to have. After you figure out the lines and such, to match up with your existing canister, then you'll have to have the system overhauled to match up with the R134a, since you have the better, in my opinion, R12. Since doing the swap for the first time, I have decided that the A/C is more of a headache than it's worth, to me. Using the 1LE pulley which is an idler that sits in place of the A/C compressor and doesn't require you to move the motor mount or pound the frame.
The power steering is another piece that'll have to be dealt with. If I remember correctly the Vette LT1 has the power steering on the passenger side, and I know for sure that the Camaro/Firebird power steering is on the passenger side as well. I installed the power steering resevoir on the passenger side inner fenderwell. It was nice and easy, and looks good there. It also allowed for some easy routing of the lines for it, which I made on my own.
The fuel lines will have to be modified as well. The lines come up on the driver's side of both engines, in the rear, by the fuel pressure regulator, which happens to be another piece that I recommend you upgrade. To an adjustable one, that is. Again, I got mine from TPIS. TPIS claims something like a 10hp increase, when adjusted correctly. It's a very easy install, 10 minutes or so. One thing that I did that I'd recommend is to change the fuel line fittings to -6AN, by Aeroquip. It makes it very easy to run your lines. The stock in-car lines follow the frame up on the driver's side, and aren't very flexible, and the LT1 lines are form shaped to aim towards the passenger side fender. So the use of braided or equivalent lines makes it a lot easier to hook them up. All you have to do is attach the fittings on the end of the lines, and one onto the end of the return line on the fuel rail, and then use a small adapter to connect one line to the fuel pressure regulator. The braided lines look cool too!
Along with changing the fuel lines, if you aren't starting with a TPI car you need to upgrade your fuel pump. The TPI cars have a pump that's capable of supplying an LT1, but other engines' pumps are not. Again, TPIS offers a pump that is more than capable for meeting the needs of an LT1, even a heavily moddified LT1. It's an intank Bosch unit.
The radiator is another thing that has to be converted. I got my hands on a '95 LT1 radiator and dual fan set up. The dual fans are a necessity, with the high cooling demands of the LT1. The radiator is needed because of the multitude of coolant lines that are needed to keep the reverse cooled LT1 cool. It happens to be skinner than the stock 3rd Gen. radiator, so I had to cut my stock radiator cover and narrow it and then fit it back together. It looks as if it's supposed to be that way. You can't even see the cut, without staring at it or looking for it.
Another thing that I did was, purchase a Modified/Ported Mass AirFlow Sensor. I bought, again, TPIS's offering. They increase airflow dramatically: 750 CFM, up from 529CFM stock! You can also get them in higher CFM amounts, in 100CFM increments all the way up to 1400CFM. But between the MAF and the throttle body, you'll need something. I purchased the Corvette LT4 bellows w/IAT sensor. These bellows pretty much replace what your stock ones look like (assuming you have/had TPI). You can then connect the bellows with your stock air intake set-up.
Another thing that you can do to increase performance is to install a Throttle Body Airfoil. Not to beat a dead horse, but I purchased TPIS's airfoil as well. They were the first to have it and have spent thousands of hours on the flowbench, perfecting it. They claim an 11.8hp average increase and 9 lb-ft of torque increase. Very easy install, just another 10 minutes
Since first swapping my LT1 back in '99, I have changed a few things, over time. First thing that I changed was the ECU and harness. I have since changed to a '93 ECU and wiring harness, running Speed Density. TPIS was so nice as to exchange my '94 ECU and harness for a '93 ECU and harness. The '93's used a 700R4, so it naturally worked better with the auto that I had initially. With that I needed to get a special speed sensor/speedometer drive unit. The '93's had an electronic speedometer, and the 3rd Gens. have cable driven ones. The unit allows you to use the '93 ECU and a cable to drive the speedometer, very slick. With the '93 set-up, came the demise of my MAF, reason being that the '93's were a Speed Density system. So I also no longer needed my LT4 air bellows, instead I purchased a '91-'92 TPI air bellows. They are longer, and consequently, more flexible. The flexibility allows you to bend it up to either your stock air cleaner set up. I also incorporated a 2.8 liter Camaro air filter housing. Since I changed to a Speed Density system, I had to relocate the IAT (Intake Air Temperature sensor) and the 2.8 has a place for it in the housing. It's very slick, and doesn't cost any performance, and instead "adds" it.
I have done quite a few more things to my car, some that aren't incorporated into this document. I am now running a T56 (6 speed transmission) with a McLeod Street Twin clutch. Fun times, I tell you...A LOT better than running an auto, in my opinion.
Well, that's about all I can think of right now. I hope this has been of help to you...and I also hope that you don't think that in writing this that I'm talking down to you, if you already know some of what I said. The opposite, as well. I hope none of what I said was over your head, if it was either way, let me know and I'll do my best to help 'ya out. If there is something that you'd like me to clarify, or if you have any questions, you can e-mail me at the link below and I'll try and answer it to the best of my ability. Good Luck!
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LT1 Swap Pictures/Explanations