The Stovebolt Site Forums The Shop Area The HiPo Shop Cadillac motors into AD trucks

Someone asked me about my Cadillac engine swap and I thought it would be appropriate to post here and find out if anyone else has or is using a Cadillac in their '47 to '54 GM truck.

How about it? Anyone else admit to running a Cadillac? (I could name two or three others, but I'd rather let you self-identify.)

If so, what can you tell us that will help others be successful with this swap?

I'm putting a '76 Cadillac 500 with TH400 into a '54 GMC 1-ton. The frame on a 1-ton is a little different than the smaller trucks, but the sheet metal is the same as any other GMC and very similar to the Chevys.

The motor I plan to run came from a RWD car and I have the exhaust manifolds that were on the car. I also have a 500 from an Eldorado with the rear sump pan so I'm good on those details.

I test fit my motor and then pulled it out, pulled the cab off, and then started my IFS swap. I've not finished the IFS swap so haven't put the motor back in yet.

While I had it in place I determine that I would have to lift the cab, cut the floor in the toe board area, or remove the bell housing crossmember. Since I'm going IFS I decided to remove the crossmember.

I expect to either go with a remote oil filter to notch the front crossmember to clear the oil filter. I've not done this yet, and because I've put a power steering box on the outside of the frame near that crossmember I'm thinking I need to preserve the strength and regidity that crossmember brings.

The other challenge I could see in the mock-up stage is that the exhaust manifold on the passenger side exits far enough out from the motor that frame clearance might be a problem. I might be able to raise the motor some, but that raises the center of gravity and moves the motor back into the floor. I've seen other swaps where the builder trimmed the frame. I'm trying to avoid that approach.

What have you learned or what challenges are you facing on your Cadillac swap?

And a bonus question: Why a Cadillac motor?

Why not use a 4L80E trans, it is a TH400 with overdrive, good on the highway...
It is an electronic trans but you can get what is needed to run it behind a non-computer engine, either some OEM computer or aftermarket.

There is no 4l80e transmission out there with the Buick Olds Pontiac Cadillac bellhousing that I am aware of. The Caddy 500 could easily push out 400 ft/lbs of torque. I am not sure the above transmission could handle that much torque. I believe the TH400 that came with the caddy is up to the job with a 3.08 rear end.

Why not use an oil filter relocation kit, and mount the oil filter somewhere easier to get to and out of the way of that crossmember?

I haven't done the caddy 500 swap, but I wanted to in my first 59 gmc. I still have a poncho alluminum 4 speed bellhousing that I was gonna fit to the rear of that caddy.

I think it would be interesting to note that when the caddy 500 came out in 1970 it was rated for 400 HP. In 1976, the last year of production, the 500 was only rated for 190 HP. 1970 had a compression ratio of about 10.5:1 while 1976 was reduced to 8.5:1. The later 500s had an HEI ignition. I don't remember which heads are suppose to flow the best, but some are better than others. Any 500 caddy can be rebuilt to be a Monster, of corse it usually costs a little bit more than building a chevy.

A couple of reasons.

First the cost of the 4l80e and related stuff new was going to be three or four thousand against using a BOPC TH400 I already had. I don't expect to use the finished truck enough that it would pay back that investment in any reasonable time.

Yeah buying the transmission used could save much of that, but even looking at just the cost of the computer with harness and the Cadillac adapter the conclusion would be the same. And buying a used transmission risks needing to rebuild one, and the 4l80e isn't as easy as something like the TH400.

And second I plan to use this truck to pull my trailer and it will rarely go far without a load behind it. The combination of tires and rear gears put the motor in the ideal RPM range at freeway speeds already.

An OD tranny doesn't gain me anything with the big Cadillac motor in my application. If this truck was to be a daily driver I might make a difference choice, but I don't think it makes sense based on my current plans.

I have one of those Pontiac bell housings too. If the right flywheel were easy and cheap to come by I might put it to use behind a Cadillac but not this project. I actually have two 500s and a 472.

The '70 500 was the highest rated of them all. Two things happened over the next few years. The compression was dropped and the horsepower rating system was changed. More of that drop is the result of the change in rating system than the lowered compression.

There are basically two sets of heads. The earlier ones have smaller chambers and flow better than the later ones. My '76 motor is the last year the 500 was offered, it has the HEI and larger chamber heads. It also has only about 70,000 miles on it.

Based on my research an intake manifold and cam change will bring back more than enough torque to do the job without requiring turning the motor more than 3500 RPM at any time. There is no substitute for cubic inches.

The project isn't finished yet so I have no experience of my own that proves this will be satisfactory but I'm optimistic.

I can't comment about the swap, only about the motor.
IMHO this is an excellent choice for a truck. The torque range is biased to work best at low RPM, the engine is light and narrow for its size. It will pull very tall gears with a lot of weight (my 425" Coupe de Ville had 2.23 gears, weighed easily 4,500).

Not an AD,but my 1965 has a 500 cu.in. Caddy,and a 400 Turbo Hydramatic.It was already in the truck when I bought it. It is a pleasure to drive,and not too much performance but she gets right along down the road.And Oh yeah,with a dual exhaust with turbo mufflers it sounds really mean.

How much does the caddy weigh? I have heard cad motors (some of them) are or were built with a higher concentration of nickel that would mean less ring wear.

The Caddy weighs less than the Stovebolt, or GMC six in my case, that it replaces. Its about 650 pounds depending on exactly how its set up.

They are a high nickel content block and reports are that they go a long way before showing any real wear. Your question implies a timing question and I don't really know much about any Caddy motors except the 472/500 so I won't try to respond outside that context.

Don't forget to post some pics of your progress.

What progress? I haven't been able to do much on it for months.

This last couple of weeks have been better, but I've been working on the IFS swap and in order to finalize suspension mount locations decided to replace the bushings and pins in the rear suspension first.

That has turned into a three week project that isn't done yet and today I had to order more parts because the box of stuff I thought would do the trick proved not to have everything I needed.

I need to get the rear suspension back together, finish locating and mounting the IFS and steering, and then I'll be back to mounting the motor and transmission. I plan to drop the cab back on the frame to be sure I don't create more problems with my motor location....

I guess I'm moving ahead, but today when I discovered I didn't have all the bushings I thought I did was a discouraging day. Oh well.

I am in the process of putting together a 54 3100 using a caddy motor and a th400.

It's still in the early stages but I hope to have it driveable by the summer.

Brian tell us more about your plans. How are you approaching the steering clearance issue? What are you using for exhaust? Cooling system?

If yours is drivable by summer you'll will finish yours long before mine is done. Mine might be finished by summer 2011 but don't hold your breath!

plan on doing the same swap on the 53. will keep 1 eye on this and your progress. mine will be down the line still have the 50 to get done this year. then onto the 52 will work on the 53 in spare time (if there is any) good luck with the project and keep us all posted

Have done a 53 Chevy 1/2T (no pics) and a 51 GMC which you have seen photos of. Have an early 50's GMC coming in that has been converted into a 4dr PU to use as a car toter. Fellow is very unhappy with a Ramjet 350 crate engine for use in a tow vehicle and wants a 500 Cad after using the 53 with the 500 for one trip. I told him a 502 would go in much easier since it's in the same family but he likes the Cad. The gearing is way too deep for a Caddy, 4.88 under/3.42 over, but that's not a problem. I am going to use the new electric power steering since it's all inside the cab in the column and no pump, hoses, belts, or brackets plus with a short 16" column the 3/4 steering shaft can be angled way over to the left kick panel and through a pillow bearing. This definitely helps with steering box and exhaust. I have a 37 Chev 2T sheet metal on a UD chassis (Nissan heavy truck division) with this set up and pics if anyone is interested. For radiators I use 46/47 Ford flathead six truck units and they cool in Texas with the a/c on. A radiator of the same dimensions with the same fin and tube count would work I'm sure.

Coilover what transmission do you plan to use behind the 500?

I'm using a TH400 (no overdrive) and 3.42 gears in my 1-ton trailer puller. With 31 inch tall tires I expect it to work out about right, but would be curious what you think.

Since mine will rarely be on the highway unless towing I don't feel the cost of an overdrive is justified in my case.

It had a TH400 which was my choice which I was going to mate with a 2 speed rear end. The owner was convinced by the guys at Phoenix that they can build a 700R4 that with the recommended cooler will hold up. It is going to have an aluminum roll back bed and will haul either his 37 business coupe or one of his 62 409 cars. The 62's are big cars, probably in the 3800 to 4000 pound range and the truck itself is probably going to weigh 12-15k with all the chains, boomers, straps, etc. This is still under 20k so the truck is going to have an easy life compared to one hauling commercial loads.

Phoenix is supposed to be good smart transmission people, but I'm not sure I would trust them on this one.

If GM were building this truck it would have either a 4L80e or an Allison, definitely not the 4L60 or 700r4.

I have a 350 powered 4200 pound truck with a 700r4 that is failing I'm sure at least in part because of the load its been asked to move.

Phoenix is where I got my 700R4. As said out here in the country, "Never heard a discouraging word" about them. Their strongest 700R4 is rated at 575 horses and 600 lbs. of torque.
I wouldn't think a stock 700R4 would hold up to pulling a lot of weight over long periods..

I hear you. While I'm not a big fan of add-on overdrives, I think I'd add a Gear Vendors to my TH400 before going with a 700r4 in my tow rig. I'm hesitant to run a 4L80e mostly because of that little 'e' and the expense and complication associated with that.

If Phoenix says it will work and warranties their work I'm not going to argue. But I'm also not likely to buy.

Steve,
Why not a 5 speed w/OD?

In someone else's truck that would be fine. In mine, no.

The big Cadillac was never offered with a manual transmission, so the crank has to be drilled for the bushing and there is no factory flywheel that fits.

There is an aftermarket flywheel available but it is spendy. A BOPC bellhousing will work, though I understand not all of them support the Cadillac starter.

So once you're that far you need a manual transmission that can deal with 500 foot pounds plus of torque. The New Venture and ZF transmissions don't seem to be real good choices and suddenly you have very few good options.

Aside from the fact I'm not a fan of manual transmissions getting one behind a Cadillac doesn't strike me as a project I want to take on.

Yeah but you'd be one big "odd ball".

If you put it to a vote I might already be considered such. I certainly don't need to go out of my way to create that impression.

Steve,

There are ways to put manual transmissions behind a Caddy. http://www.cad500parts.com/catalog/page27.htm. This is the same approach that I am using to put a manual trans behind a Northstar. The flywheels carry the pilot bushing. This approach is also done by most of the VAG cars.

I myself am running a Big Block Olds. It started life in an olds 98 that got totaled. Then spend a while in an 81 half ton Chev pulling a stock car trailer. Now its sitting on a skid awaiting to go into my '48

As for exhaust. You own a welder, make your own headers. That is what I am doing. The good news is that you dont have siamesed exhaust ports, so you can start with a set of BBC headers and change the flanges.

The trans I have is a TH400, however seriously looking at a TKO-500 or even a 4L80e with a trans adapter and stand-alone. Most likely, to get the truck rolling, I will stick with the TH400 for now.

I don't want a manual trans in my truck. This morning I was forced to drive for maybe the third time in five months and since my 4-speed Corvette was the only car home I used it. After only five miles my left knee was in pain. My health would have to improve a lot before I would choose a manual.

Corvette you say? Heck, if I lived in Seattle I'd be you chauffeur.

Unsure, I have to get the motor located and go from there. The previous owner had a different front clip from a mid 90's pickup welded on. The steering box is not there. Also, there are small block mounts mouned direcly on the cradle. I get the heads back next week and will be putting the motor together.

Manual transmissions- - - - -hand cranks- - - - -kerosene or acetyline headlights, clincher-rim wheels, and the "one-man top" that took three men and a small boy to put it up or down- - - - -they're all the same degree of obsolete! If people were intended to drive stick shifts, they would have been born with three legs!
Jerry

This forum is such a grin!
To fan the flames, all I can say is: hot rods have sticks...automatics are for girls.

cm

and for old cripple guys who's left knee won't let them drive sticks anymore...joe

Yeah Joe, unfortunately I increasingly resemble that remark.

Starfire4 tell us about your Cadillac powered project with a manual. I want to know where you got your flywheel and what you did about the pilot shaft bushing problem.

Heh, heh. No Caddy for me, yet. But I do have access to a couple mid-sixties Lincolns...hmmm. Maybe when gas gets cheap and I run out of Chevys.
I suppose we work with what we got, and with what we like.

cm

Some of us are ahem.....Gifted...

Well, made some progress this week. First of all, got the truck titled and licensed. Turned out not to be too big of a deal, went to the Sec of State office here in Chicago with my various pieces of documentation, they scratched their heads a few times, pulled out the big rubber stamp and gave me a title and plates.
Second, got the Caddy 500 engine back from the shop. I had the heads done, and the clearences checked on the pistons and the rod and main bearings. They found one bad piston, a cracked ring land, and sugessted a new cam because of lobe wear. Otherwise, looks good. Now I have to assemble and order a hot cam.
Finally, I picked up a steering box from a Bravada, bolted that in place, and today I was at a local U Pull It boneyard, and picked up a sliding shaft that fit like a glove between the box and the end of the column. I have steering.
Now I can start fitting the motor and trans.

Sounds like you have the Midas touch.

Brian sounds like you're making great progress!

Cam gears and chain? Oil pump? Those are items my research says should also be replaced before putting one of these old motors back into service.

The first block I picked up came out of a 76 Eldo. When I pulled it apart the bearings were spun. I put that one on the shelf. I then found another block on ebay. I bought it from a guy who bought if from a guy that supposedly rebuilt it with new bearings, rings, timing chain and water pump, and a MTS #5 cam. That's the block I'm using and it was pretty well as represented. The timing chain and water pump were new, the bearings and rings looked new. I took it to Engine Rebuilders out in Stone Park to have them check the clearences and they found the couple of issues. Overall not too bad. I also talked to Marty at MTS about the oil pump, he said if the case does not look grooved it should be OK to use. I'll fire it up and keep an eye on the oil pressure.
I put the rotating assembly together today and will fit the trans tomorrow.

I've got three motors. A 472 that is completely disasembled and which I assume needs complete rebuild, a 500 represented as a solid motor but who knows, and a low mileage 500 I drove home and know sounded and ran nice.

I'll be putting a new cam (MTS 3 or 5), cam chain and gears, probably an oil pump and the Edelbrock manifold on it.

Hopefully I've correctly analyzed what I have!

The nice thing about these Caddy motors is the ability to make alot of torque without getting exotic and spending alot of money. Torque is what makes a vehicle fun to drive, at least in my humble opinion. As a plus they are not to oversized or heavy.
Make sure you check out the forums at http://forums.500cid.com/ for information on these motors.