Thanks...
You have probably the toughest car to work with. This is the easiest and most correct way to do this;
Buy a somewhat usable and running 1977-1980 cadillac fleetwood. You can defiantly find one of these for a few hundered. My suggestions is to spend about 800-1000 and find the best you can as it sounds like your car is pretty nice and most of the parts from this car will have to go into yours.
Take out your HT4100, your TH200 and your 7.5 differential and sell them for whatever you can get. 1.00 is good enough and whoever is buying is not getting a deal at that. I doubt you are a machine shop, so a turn key motor is the simplest way to go if you want the most power. Have someone build you a 500, like MTS or whoever reputable... Get the eldbrock intake for it and some 70-73 RWD manafolds. If you dont want to spend 4000-6000 bucks to get a true 500HP engine that is balanced, etc, with the best hardware avalible, then just nab a good running 500 from the wrecking yard with nothing attached except the carb. Put a small cam and the edlebrock intake on it..... If you want to, you can put the heads from a 425 on it and give it a bit more power as it will raise the compression, but this is kind of a rig... I would mill the 500 heads as much as you can to raise the compression. By doing this you will have a near 400HP engine for a just several 100 bucks and a bit of work. Put new gaskets, timing chain, oil pump, etc, and you will have a good motor as these suckers last forever, even it the motor has 100K on it when you get it. This is good cheap fun and works darn well.
Take everything from the donar car you bought except the motor and put in on your 500. Sell the 425 or 368 from your donar car if you like. Use the Brackets, AC, Alt, PS, all of it... Use the carb from the 500 and rebuild it right. Put a new fuel pump on the 500. Take the gas tank from your donar car and switch it from your 4100 car. You have an electric pump, and the 500 uses a mechanical or low pressure electric. Gas tank is easy swap since you have it from your donar. Take the TH400 from the donar car, put a front and rear seal in it, change the fluid from the trans and converter, put a shift kit like a B&M trans pack in it and put it behind the 500 with all the 77-80 parts on it and put them both in the car at the same time. Put some 2:73 to 3:08 gears in the 77-80 differential, if it does not have it already, from your donar car and put it in your good car. Use the big driveshaft from the 77-80 car too. Put the front springs from the donar car in your good HT4100 car as your car now has a heavier engine and needs this....
Unfortunatly there are not many direct tranplants for a 4100. This method mentioned, with alot of time and effort will get you a nice powerfull car set up correctly with the entire driveline capable of handeling the power.... Not easy, but this is how its done correctly and as cheap as possible.
Just for an analogy, it would be just as easier to put a CAD 500 in a 79 TA rather than a HT4100 car as the hardware is so bad to begin with in the HT4100, but if the car is as nice as yours sounds, I would not hesitate to do it right should this be something you desire. If its too much for you... It might be easier and cheaper to sell the car, get the nicest 80 or 81 as its pretty much done for you already. You can also get a 90-92 5.7 car and put a chevy 502 in it easier than redoing a 4100 correctly.
Deep Sleep said:
O.K., Just left your 500 cid webpage so now I know what the rims are. Thats one sweet ride. I'll have to get some pics of my caddys up here. Got to have that 500 in the Fleetwood Brougham!!!!