LT1 conversion

[Dr.Feelgood]

So due to the outrageous prices on 365 motors for my 58 caddy, Ive decided to drop an LT1 in it instead. I was wondering if anybody else here has done this, and if so would you recommend it. Cupcake said I would need motor and trans mounts for sure, and a shortened drive shaft. Does anyone know what else this would entail?

Also, thanks to Spastic Chicken for the Scarebird link, I'll be doing the disc conversion as well!

[Dickey]

Any particular reason for wanting an LT1 motor? I only ask as they are generally harder/more expensive to find go fast parts for than a first or third gen SBC and do not make nearly as much power as the later LS motors. That said, you'll need to appreciate that your coolant will flow backwards compared to what is expected for your radiator. The water pump puts water through the heads first and then it exits through the block. GM put this back to the way God intended with the LS series engines. What transmission are you running with your LT1? If you're going to be fabbing frame mounts to attach sbc style block mounts to, why not just set it where you won't need to do anything with the driveshaft other than change out the yoke? A 700r4, which is commonly found bolted to the LT1 engines, is just under 31" long. The hydramatic is in the neighborhood of 32 if I recall correctly. I'll make a point to measure it next time I'm under there but I'd be surprised to find such a difference that you couldn't address the driveshaft length with a minor adjustment to the engine placement. Shifting will be awkward. Do you plan on using a modern cable style shifter to manage the newer transmission? You may be able to fab up some manner of specially shaped rod to make use of the column shifter though. On tri-five Chevy's this piece is readily available so that later model transmissions can be shifted with a stock powerglide column shifter; I would not bet that you can find such an animal for purchase on a 58 Cadillac. The rear transmission mount is a minor affair. Even if you had to make a new one it is only a few bolt holes and a slot to allow the parking brake cable through.

[Dr.Feelgood]

I hadnt thought about the LS. I figured I would use the motor out of a 95 limo parts car my friend has.

[60Crown]

'95 limo parts car??? Tell me the windshield is good. And available.

[Dickey]

Ah, then I understand. The transmission in that car is a 4L60e which is the successor to the 700r4, or a 4L80e which followed the th400. Basically the transmission is shifted by a computer and the older style Throttle Valve (tv) cable for indicating throttle position to determine shift details is no longer used nor does it have a vacuum canister for determining shift points. You will need to pull everything electronic over from that 95 to make it work. Given that it is pre-ODBii, I don't think you will have a problem with excessive chatter to and from the body computer or anything like that. The ignition key chip thing is likely the largest hassle you'll come across and there are numerous articles on how to bypass it if you do not want to transfer the functionality over to your 58.

Were I in your position, I'd still try and find a 472/500 with a th400. Obviously I have no idea what kind of a deal you are getting on the LT1 but unless you're saving more than 1000 dollars, I don't think you'll come out ahead with regards to your time expense vs a simpler engine/transmission purchase. Furthering that thought, you'd likely be happier with the Cadillac motor as it generates a considerable amount of torque under 1800rpm and no small block will be able to touch that. In a 6000lb car with 3.08 gears, a lack of low end grunt will be noticeable.

edit - neuro flatulence; did not mean to use the word predecessor

[Abnorml]

'95 limo parts car??? Tell me the windshield is good. And available.

Yes, VERY hard to find. I have a friend that got her 94 hearse's windshield broke during a hail storm. Can't find a replacement.

[Dr.Feelgood]

The engine, trans and computer components together are $900. It was too cheap to pass up! but now Im wondering why its so cheap... And I had that same thought about the power of the cad block vs the small block. I guess the Idea of fuel injection caught my attention. the 472 was on my list of possible candidates at first, but then I decided to go either original or efficient. Now Im torn again...

I'll ask about the windshield.

[kshearsedriver]

Better MPGs to be had from the LT1 and 4l60 for sure though opposed to a big Cad engine and still more power than the 58 had stock. Not sure how much difference there is between the chassis of the 58 and a 62, but I installed a TBI 350/700r4 a few years ago in a S&S combo. Wasn't too hard overall.

[Dickey]

A 365 in 1958 boasted 335hp, and over 400ft/lbs of torque. An LT1 out of a 1995 professional car would be in the neighborhood of 280hp and 300ft/lbs of torque.

[60Crown]

And those figures are for the detuned LT1 found in '94-'96 procars, correct?

[Dickey]

So far as I know, the corvette was the only mobile with the hot motor from 94 to 96. I took the liberty of assuming his drivetrain came out of a stock 1995 limo.


edit - found some information on the matter:
http://consumerguideauto.howstuffwor...leetwood-6.htm

Initial Fleetwoods were powered by a version of GM's venerable 5.7-liter V8, developing 185 horsepower. A 4-speed automatic with hydraulic controls was the only transmission. A massive power boost (to 260 horsepower) came for '94, courtesy of a Corvette-based V8 engine. Also 5.7 liters in displacement, the LT1 engine used sequential fuel injection and drove a new 4-speed automatic transmission that featured electronic controls.

Engines	Size liters / cu. in	Horsepower / Torque	Transmission: EPA city/hgwy	Consumer Guide Observed
ohv V8	5.7 / 350	185 / 300	4-speed automatic: 16/25	4-speed automatic: --
ohv V8	5.7 / 350	260 / 330-335	4-speed automatic: 17/26	4-speed automatic: 14.8

Also, 'detuned' is a bit of a misnomer. It isn't like there is some manner of adjustment you could make on the limo engine to suddenly gain an additional 40hp and 10 ft/lbs of torque to what the y body had. We're talking wholly different cam shaft, cylinder heads, intake, exhaust and engine controls. Even with that though, the 365 outguns the LT1's power output.

[60Crown]

Hmm. From Wikipedia:

The 1992 LT1 in the Y-body was factory rated at 300 hp (220 kW) and 330 lb·ft (447 N·m). 96 LT1 Y-bodies were rated at 300 hp (220 kW) and 340 lb·ft (461 N·m). The 93–95 F-bodies were rated at 275 horsepower (205 kW) and 325 lb·ft (441 N·m), while the 96–97 cars were rated at 285 horsepower (213 kW) and 335 lb·ft (454 N·m). The 96–97 WS6 and SS F-bodies were rated at 305 hp (227 kW). The 94–96 B and D-body version was rated at 260 horsepower (190 kW) and 330 lb·ft (447 N·m).

I'm curious now if D-body (Cadillac Fleetwood) commercial chassis received this lesser version, or perhaps one from a B or F-body to offset additional weight. Would checking motor number provide insight?

[Dickey]

I suspect you'd get more information from the data plate in the glove box. For GM cars, there is a grid of codes on a sticker that defines what options were with the car when it came out of the factory. In all honesty, I can't imagine GM offering anything other than what would be found in a typical Fleetwood of that year. There were a lot of marketing shenanigans with regards to power output figures back then.

[pyro]

As long as you have the block you need, you can put any part that you want into it. Different heads and pistons are going to change everything.

[Dickey]

That's true of any engine, including a 365.

I was only pointing out that the original motor from the 58 would make considerably more power than the LT1 Dr. Feelgood has because someone stated otherwise. For that matter it makes a bit more than any of the LT1 offerings GM had in 1995. I'm not sure why this thread took the direction it did, I just intended to correct a bit of misinformation is all.