The Stovebolt Site Forums The Shop Area The HiPo Shop Making a Cadillac 500 fit in a '54 GMC

I've been working toward putting a Cadillac 500 in my '54 GMC 1-ton. Today I did the first trial fit and have a question or two for anyone else who has tried to use a big Cadillac in one of these trucks.

This was a first trial, aside from removing the steering column and gear, I've not changed anything.

It looks like I need to at least modify, if not remove the bellhousing crossmember to fit the transmission. And I need to do something to make the oil filter fit and it looks like either modifying the front crossmember or using a remote filter.

Anyone have experience with any of these approaches? I've love to hear what you did and even study some pictures!

I'm considering using the Caddy 500/TH400 setup in a 59 Burb, but I'm not past the planning stage yet. Do you intend to keep the straight axle/leaf spring front suspension? If so, I'd suggest modifying the bellhousing crossmember rather than removing it, as it also provides frame stiffening near the back of the leaf springs. Removing it altogether might result in some unwanted frame flexing as the springs absorb driving loads. Just a thought, as I haven't worked with this type of swap yet. The remote filter setup will probably be preferrable to chopping on the front crossmember, IMHO.
Jerry

Cant really help you with the install,but the 500 Caddy is a nice running engine.I have a 65 1/2 ton with a 500 Caddy and 400 Turbo,but it was already in the truck when I bought it.

Here's a picture of the cross member I used after I removed the original one at the back of the engine:
http://rides.webshots.com/photo/2236622090080251109tywgjR
The new U shaped cross member is from the 78 GMC 6500 truck I got my engine from. I did narrow it a few inches and make the pieces of channel to bolt in the frame to then bolt the cross member to.

I am also using a remote oil filter, works fine. But not sure what your options are for a remote oil filer are?

Grigg

Jerry this was my first real step transitioning from planning to building. My brother was visiting for the holiday and we just got carried away 'playing' in the shop. I feel pretty committed to going the Cadillac direction, since I now own two 500's, but if the issues are insurmountable I want to know before I make changes that can not be reversed.

I share some resistance to comletely removing the bellhousing crossmember and since I know others have used this motor I'm hoping to learn what they did before making a plan.

Regarding the front crossmember I'm a bit less concerned. The stock crossmember appears to perform three functions (1) tie the front together providing strength and stiffness at the front of the springs, (2) mount the radiator and front sheetmetal and (3) mount the motor.

In my application the motor will be sidemounted somewhat behind the original crossmember location, and I think loosing the back few inches would not be a cause for concern. Of course that presumes my motor mount solution does not cause new problems.

Dale on your truck things are quite a bit different. You have a single big crossember that mounts the suspension and is the stock location for motor mounts. The 500's mounts are probably further forward, but not a lot. If the truck was a manual it had the same type of bellhousing crossmember, that I'd bet its been removed. And I believe the stock type automatic crossmember can be moved to work in your truck. I'm glad you are pleased with the way it operates, that confirms what I expect with mine.

There is at least one Stovebolter running a Cadillac 500 in an Advance Design truck which I believe has an original frame. I'm hoping any guys with that setup will speak up!

Grigg apparently I was already busy writing my previous post when you responded.

I like the crossmember you've shown. I'm not sure I'd go looking for exactly that one, but I can imagine making up something similar using square or perhaps rectangular tube to keep some structure in place, but get it below the new transmission.

Thanks.

Our holiday guests have all left in the past hour, and I've done my part in getting the house back to normal, so I'm going to take some pictures of what we've done to facilitate talking about what's next.

Steve,

I commend you for using something other than an SBC. The caddy 500 is a good torque monster, and there are plenty of low $ performance tips.

The bell housing cross member will need to be removed based on test fitting of my BBO in my '48. I will be making a new rear cross member, and the front engine mounts will be attached to my IFS crossmember for a 3-pt mounting system

That is all I can offer at this point.

Scott

Scott I intend to use the finished truck to pull a trailer. My alternative choice if I were not to go Cadillac would be Big Block Chevy. I too am tired of SBC's, though today three of my drivers are 350's, and I have eight more I could use someday.

BBO is big block Olds I assume. Are you using a BOP TH400? Because of the change in mount design the crossmember you've removed is a little different than the one in my way.

What are you doing for exhaust manifolds? I don't have the motor close enough to its final location yet to be sure, but I suspect that is going to give me fits too.

The 216 was a heavy engine but I wonder how much heaver the cad will be. Will you need to beef up your front suspension?

What does a 216 have to do with it? The original motor in a '54 GMC was a Jimmy 248.

The 500 Cad weighs on a little more than a small block Chevy. There will be no need to beef up the front suspension. Brakes yes, suspension no.

- Yes, 455 Cubic Inches of low speed high torque goodness. There are plenty of cam options for what I am looking to do as well.

I have it, vascillating between the TH 400 or a Tremic (either TKO or T56 retro) Will most likely use the TH400 initially as I still have two mortgages and money is a little tight

The stock manifolds flow ok, however are limited in configuration, so most likely I will be using headers, either stock Cutlass units, or building mine from http://www.speedwaymotors.com/1-1and2-OD-ASSORTED-BENDS,1731.html or by taking a set of SBC 2" primary headers and swapping the flanges.

Scott

Scott I talked to a transmission guy at a Good-Guys show last summer who said they could provide a 4L80e to fit my Cadillac. I would imagine that same trans would fit your Olds and cost would be similiar to the Tremac.

I'm bulding a truck to pull a trailer. From the sound of your transmission choices I think you are building a hot rod. We'll deal with similar issues, but likely choose different solutions. Right now I plan to use the TH400 because I have it and don't want to spend the bucks for the OD automatic.

I've considered a Tremac for my old 'vette, but as you say money is tight and I'm just glad I don't feel the need to sell any toys!

Steve,
On the rear crossmember, several fit between the rails from the various sizes of trucks, they just mount different. I found when building Brads 1 ton panel, that someone cut out his crossmember. I found one out of a 2 ton to replace his 1 ton's cut piece. Not sure, but I think it dropped a little lower which helped me out when installing his V-8. The good part, it all looks factory, nothing homemade looking. Regardless, I'm sure a factory one could be modified to work,
Scott

Thanks Scott. I was also thinking that maybe I could just remount the stock crossmember an inch or two lower, leaving a mostly stock appearence.

Another thought I had was to cut the floor of the cab. Then mount the motor high enough that the crossmember is not a problem, and I can use the stock exhast manifolds.

I believe that is a standard latemodel 4L80e with an adapter. Unless a special case was made that I do not know about, the 4l80e never had a BOPC bolt pattern. You may want to ask. the only thing special would be the trans controller which are easy to find.

No, I just dont like automatics, and would like an overdrive trans. My intention is to build a truck to pull my boat, haul parts and generally drive it.

If I dont sell the house in WI within a few months, I may have to - I feel like the guy in the lending tree commercials. "i'm in debt up to my eyeballs, somebody help me..."

Okay I did a little research to verify my statements regarding weight of the 500 with TH400 versus the GMC 248 with SM 420. Here is what I found.

Cadillac as removed from car is about 670 pounds. Numbers I found varied from about 600 to over 700, but the 670 seemed most credible.

TH400 weighs about 150.

I didn't quickly find a published weight for the GMC 248 that came in this truck, but if I use the Chevy 235 value of 640 pounds I should be under the weight of the physically larger 248, but not by much.

The SM420 weighs about 135 pounds and that does not include the bellhousing, clutch and flywheel.

So while my numbers are incomplete, my conclusion is that I am correct, the total weight is not increasing enough to matter, and could even be decreasing, but again, not by enough to matter.

670 plus 150 is 830 for the Cadillac powertrain.

640 plus 135 is only 775, but does not include the bellhousing and clutch nor account for the difference between a 235 and 248. If those add just 55 pounds the two weigh the same. But even if the Cadillac combo proved to be 50 pounds heavier I'm not worried about suspension being able to handle it.

No suspension worries. But then read my next post...

Steve, you are correct on the mass of the Caddy fat-block, however the weight you have for the caddy is fully dressed with cast iron intake. Remove 35# if you go with an aluminum intake. Also, remove the mass of the freon compressor if you go without A/C

I've been looking at the motor as it sets in the frame and considering my options.

The path I'm pursuing is to remove the cab so I can play with motor and trans location with out hitting the floor and firewall, and I can better see the interference with the frame and crossmembers. I already marked firewall and toeboard/floorboard locations on the frame.

I've decided I'd rather modify the floor and firewall to deal with a higher motor than modify crossmembers. So I'll get the motor located where the frame, crossmembers and exhaust manifolds all look workable. Then evaluate what that would do to the cab.

If that approach does not produce a satisfying result I have a fall back approach in mind.

Remove the entire stock front suspension including that troublesome crossmember and use the IFS from a '72 Chevy C20. I'd really prefer to go IFS anyway, and a disk brake conversion is definitely part of the plan anyway. The IFS approach creates width issues, so its not been my first option. But going that route does solve the crossmember issue, while adding power steering and disk brakes.

And the crossmember I have came from a big block truck, so its already sprung for more weight than my Caddy motor.

So that is where my head is. It will be the weekend before I do anything significant on the project, but your comments and thoughts are sure welcome in the meantime.

Scott I'm cheap. I may eventually change intake manifolds, but its not likely until I'm pulling the motor apart to put a better cam in it.

The motor I have setting in the frame does not have the air conditioning parts on it, but the one I actually plan to use is in a car with working air, and most likely I'll try to install that in the truck too...

And when you think of everything I plan to add to this truck it will not be light! But it will be less than 8800 pounds by a long shot.

Steve,
Just a thought on the exhaust and steering... My 59 GMC came from the factory with the poncho based v8. In order to clear the steering gear, the factory installed 2 right side exhaust manifolds. In other words the driver side is now a front dump exhaust manifold. Maybe you could swap the manifolds to get the exhaust around the steering gear... if that was a problem.

Steve, most of us on this site are. Hence the reason we work on these things ourselves vs paying for someone else to do the work.

With lots of weight comes need for lots of brakes.

Scott

SwingDaddy I plan to have power steering regardless of which way I go on the suspension. If I stay with the straight axle I'll use the kit that uses a 70's or 80's box, just like that I'll use if I do the IFS swap. Routing the steering column around the exhaust manifolds will be one of my challenges.

Scott I thought we all work on our own trucks because we love rust and dirt so much! While cash might keep me from paying others to work on my stuff, I get enjoy it enough to do things myself I could pay to have done.

Weight and speed compound the need for brakes. So far my plan is modern brakes from a GMC 1-ton in the rear (now in place) and either a disk conversion or the C20 IFS brakes in the front. Checking part numbers it appears the C20 brake parts are the same as a single-wheel C30. If I do a conversion I'll probably use 8-lug Dodge stuff based on what others have done.

If I intended to run this thing 100 mph I would be worried about my brakes, but loaded it may never exceed 70, which is the highest speed limit within at least 300 miles of home.

Steve,

We start working on our own stuff for a variety of reasons, mainly I believe (my opinion) because some need to for financial reasons, and others like to create with our hands and get away from life's other issues (work, spouse, family, etc.) However given my druthers of rust abatement by weeks of blood, sweet, and frustration or paying someone to do the body work now days, I think I would pay someone. Just like I find myself paying someone to change oil on my vehicles when I used to enjoy that. I do, however like taking the largest engine I can possibly find and cramming it into the smallest engine bay I can find simply because I have a welder and know how to use it. I am just a little sick of dealing with rust, solvents, VOC's etc.

Scott

For me I think its therapy as much as anything. I do stuff myself because I don't understand how I ended up with a white collar desk bound job when I'm much happier outside with dirty hands.

And then there is the ego component. I'd rather say I did it myself than I paid for it myself...

And I am cheap. I paid about $2,500 to have some work done on my Corvette a while back. When the work was done I was sick realizing how much of it was labor and that was money I could have put into tools for my shop. I could have done that work myself.

More recently I paid $4,000 for a transmission replacement in my wife's Subuaru. I could have done that one myself too, and seriously considered it, but not as much of it was labor, and since its the only car my wife will drive I would have needed to rent her a car while it was down. Safe and possibly cheaper answer was paying to have it done. And no one will ever ask who did the work on that stupid car.

But on projects like this truck, it just doesn't matter if it sets in the shop another year or two, and so I do it myself as time and money and ideas allow. Some weekends I spend more time and money on coffee and beer than the project, and that's okay with me.

I put one in a 51 GMC about 35 years ago and it now has about 250 thousand (2nd engine) virtually trouble free miles on it. The torque is fantastic and it handles 2.70 gearing with ease. I used the oil pan and pick up from a 69 Eldorado to get the deep part of the pan to the rear. I don't know how to post a picture but it is on my photobucket site at: http://s32.photobucket.com/albums/d41/coilover/
Scroll to bottom of first page and click on page 3. It is the blue truck labeled 51GMC/500Cad about halfway down page 3. The chain and sprocket steering everyone asks about is doing fine a quarter million miles later.

Evan I was hoping you would reply. I thought about sending you a PM asking you to jump in.

I see how you handled the steering, but what about the crossmembers and exhaust. Can you explain how you handled those?

I have an Eldo pan but I'm more concerned about that bellhousing crossmember at this point.

The gear head in me likes the ingenuity of the chain drive, the engineer in me is cringing.

I so well remember the constant adjustment of motorcycle chains when I was a kid, and worry about the slop in the steering from a loose chain. But a steering chain would really hardly move compared to a drive chain.

An exposed chain could be fouled by something thrown up from the road or who knows what. It does worry me but a quarter million miles is more than than anything I've built has stayed on the road, so I have to respect that. If it were me I'd probably enclose the chain.

Coilover I'm hoping you'll jump back in here with some description of your engine mounts, crossmember modifications and exhaust system.

The last time I was in Texas more than to change planes I stayed only a few miles from Plano in Richardson. If it happens again I'll want to see this truck with my own eyes!

I did this truck for a man in Plano that had a plumbing business and is now retired. He still comes by the shop about once a month so the next time I'll ask him to bring it by and we will raise it up on the rack and I'll try to get some pics. He had many crews at one time and he used the truck to go from job site to job site all over the DFW metroplex; hence the many miles. All that was ever carried in it was blue prints and paper work. I do remember the entire crossmember the bellhousing mounted on was removed. A trans mount that incorporated a couple diagonals to form a "K" member was used to regain some center of the frame rigidity. The engine mounts had to be custom made. I can't recall these but on many I use a straight length of 3/16 solid wire solder to get my profile of the bottom of the engine cushion and the upper and lower lip on the C channel frame. I can then copy this with the strap steel that is appropriate for the weight and stress. I (think) I also cut the exhaust outlets and re-aimed them. I have had very good luck welding exhaust manifolds with a mig and plain old wire, as long as the manifold shows good gray iron when tapered.

That would be great! I'll look forward to seeing those photos. Please post here when they are available.


That is an interesting idea. This afternoon I plan to remove the cab and look more carefully at the frame and crossmember.

Thanks for your ideas. I appreciate the voice of experience!

The cab is now off and I can see everything much better.

I don't think there is any way I can get the motor positioned low enough for a reasonable driveline angle without putting it at an extreme angle or removing the crossmember. Clearing the crossmember has to go.

So the question now is do I work up some kind of replacement like what Coilover did or swap the entire suspension to a '72 Chevy 3/4-ton IFS.

It appears that pushing the motor back into the firewall a couple of inches allows the oil filter to clear the front crossmember, and with the motor in that neighborhood the driver's side exhaust looks like it clears everything. The passenger side might still be a problem.

To move the oil filter does anyone make an adapter to just move it over a few inches? I can picture one, but can't remember if it's a real one, or only an imaginary one in my head? Would be pretty easy to make with a chunk of aluminum and a milling machine.

What's the concern with the driveline angle? With 137" wheel base you should have room to get that sorted out with most any reasonable engine placement?

Grigg

MTS offers a filter relocation kit which I imagine will solve that problem. (MTS Catalog)

The lowest I can get the motor while clearing that crossmember has the centerline of the output shaft about six inches about the vertical center of the of the driveline bearing location.

The Cadillac transmission is real long; the driveshaft will end up being barely more than five feet long. I'm thinking I'll run a four or five inch diameter rather than a split shaft, so I just won't have the room without cutting the k-member.

I suppose that could make as much sense as some of the other possible approaches, but unless I cut that bellhousing crossmember I'll be making major changes to the floor and firewall. I'm thinking lowering the motor is going to be more satisfying.

If I accept mounting the motor that high I fear it will adversely affect handling, and while this is a straight axle truck, I would prefer it give a feeling of confidence and predictability as it gones down the road.

But I'm eager to hear other people's ideas and suggestions!

If I remember right, these frames are just about straight. Rather than re-engineer a stock frame, why not build your own? There was a guy around a couple of years ago who did his own to mount an IFS and it turned out well if I recall. Start from scratch and put the crossmembers where needed, as dictated by engine/trans and diff.

Devin

Hello gentlemen, This is my first post on this great site. Looks like about the best truck site on the internet. Check out 500cid.com. Maximum torque specialties. These guys are the shiz when it comes to anything regarding big block Cadillacs (425,472,500). They have a great line of parts at reasonable prices, Marty and his brother are about the nicest folks you will ever meet. They are very helpful.

Welcome to the Stovebolt Ed. I'm familiar with your friends at 500cid.com and have them saved in my favorites.