Cummins or Cadillac?

[Deleted member 9101]

Caddy motor hands down!!!

My grandfather has fun them in air boats for years, they are an amazing motor.

 

[Woofwagon]

I'm thinking of running EFI, there are plenty of good aftermarket systems out there. I may have scored a Holley Pro-jection unit of 800cfm that would be perfect for a large engine such as the Cadillac.

 

[superbuickguy]

I'm thinking of running EFI, there are plenty of good aftermarket systems out there. I may have scored a Holley Pro-jection unit of 800cfm that would be perfect for a large engine such as the Cadillac.

why projection? you can simply put a BBC TBI on the Cadillac motor - the hardest part would be to machine the lower part of the distributor shaft to accept the electronics and cap of the TBI system.... don't work too hard or spend too much money - the GM system is lightyears better than the Holley. It literally would be plug and play. Pick up a BBC computer for your 'burb and you'd be dialed.

oh, and before you say it - the HEI cap for the Cadillac shares the same part number as the HEI cap for small and BB chevy.

I used to build V8 s-10 blazers - I'd buy 4.3 liter blazers for the swap because swapping in a TBI SBC into a 4.3 spot was literally as hard as changing motor mounts. The TBI plugged in, the distributor plugged in, the sensors were the same - just change the computer and bob's your uncle.

 

[MotoDave]

I'd think a 6.0 LS based (LQ9?) would be a match to the caddy engine, but probably quite a bit lighter. I wouldn't be too worried about the EFI setup, they are pretty simple. Personally would rather have a stock ECU system than an aftermarket, for reliability sake.

But just for fun, I want to see you do the Cummins swap

 

[BlueCoyote]

Interesting post. Am also considering between a BBC / Cad and a Cummins for an engineless NPR project. Like my Cummins but they are cubic $ for a 12v right now. Big CID motors can be had for little cash theses days.

 

[Woofwagon]

The Cummins swap has been done before and I've accumulated many an article on how it is done. Yet weighing the cost/weight/benefit ratios, the Caddy is looking better and better from a time and simplicity standpoint. I certainly do appreciate the info on the BBC TBI setup. Those can be had complete for really cheap. I make biodiesel for my F250 and having another vehicle to run my homebrew would definitely be a plus. However the cost involved in the Cummins, transmission, transfer case and then the body/suspension upgrades would be a bit prohibitive. I want to take this 'Burb out on expeditions here soon, not have it languish on my concrete pad for a year while saving up for all the parts.

 

[Jeep]

Having done both conversions the Caddy is dead simple with mostly factory parts, big block TBI will also work, just change the PROM and the TBI unit itself from a truck of the same year with a big block, GM parts guy with a little more than schooled knowledge would be able to help, I made a hybrid distributor from a 454 TBI distributor and the lower half of the 500 Caddy distributor. The Cummins will pound down the front end pretty good, Dana 60 swap will be down the road, the 10 bolt housing will begin to "smile" after a while especially with some rough roads, not an issue with the Caddy but it can still break a 10 bolt axle shaft easily. Both engines done right are better on fuel than stock in most cases. I've also ran the Caddy in a couple of big heavy river jets for a couple of guides, works great.

 

[Woofwagon]

Jeep, thanks for the information. I've never been much of a GM fan, but I will say this; the interchangeability of parts is awesome and the parts are plentiful. If I go with the TBI, will I have to put an O2 sensor in the loop? I"m thinking that I will, however I'm not that familiar with the TBI layout. The 350TBI runs well but it's not the strongest mule and with some of the loads I may be dealing with, torque is king. I have a 1-ton 14 bolt ready to go into the back when the time comes. It has the Eaton locker. I like the Caddy motor for the high nickel content block and the firing order is very smooth. With the right cam, I should be able to knock down 550 ft/lbs at a low RPM say around 2600 which is perfect for off road trails.

 

[superbuickguy]

Jeep, thanks for the information. I've never been much of a GM fan, but I will say this; the interchangeability of parts is awesome and the parts are plentiful. If I go with the TBI, will I have to put an O2 sensor in the loop? I"m thinking that I will, however I'm not that familiar with the TBI layout. The 350TBI runs well but it's not the strongest mule and with some of the loads I may be dealing with, torque is king. I have a 1-ton 14 bolt ready to go into the back when the time comes. It has the Eaton locker. I like the Caddy motor for the high nickel content block and the firing order is very smooth. With the right cam, I should be able to knock down 550 ft/lbs at a low RPM say around 2600 which is perfect for off road trails.

it's literally plug and play, but you do need an o2 sensor on at least one side of the motor as close to the motor as you can get.

Jeep - we've done the same thing - I used to run a 472 in a flat bottom Hallet jet. We've been swapping (my dad and I) HEIs onto all sorts of stuff using the same method you've used - though he machines, I simply cut off and either weld or screw together (depending on the metal and how clean it is). Again, with the 500, you need to swap the heads and drill the steam holes to make the 425 heads live on a 500. The stock 500 has 185 hp and 435 lb torque stock, all because it's got 7.9:1 compression. The 425 heads take the 135 cc chambers and make them 68 cc. If I were really to build an all-out motor, I'd go ahead and upsize the valves back to the 500 size, but on a torque motor, it's hardly necessary (and it would be expensive to open up, and put stellite seats on the exhaust)... then you'd get to port them to make them flow better.... all for not much gain on a torque motor.

 

[Jeep]

Absolutely guys, they work great. Drill and tap the exhaust manifold 18 x 1.5mm and screw the O2 sensor right in. It really is pretty easy and you don't even need to do any custom wiring, if you have a good dyno tuner you can get a custom prom burned for it too, probably have to damn near find an old guy as the TBI is definitely dated but dead reliable and simple. Stock prom will work but a good tuner will make a difference in the drivability. You can buy a TBI adapter to a spread bore or square bore intake, the 454 throttle body flows 670 cfm if memory serves me correct. More than enough. Superbuickguy is correct, drop a set of 425 heads on, mild cam, and you will have a tractor. A tip on the camshaft, dig up some old Crane Cams specs for a 454 Compucam and find a cam very close to those specs, preferably from Crane (I tried a ton of cams with TBI set ups) pay close attention to the lobe separation or you will have a pile of idle/low rpm drivability issues. That is if you decide to go that route, it is a cheap easy build.

 

[redthies]

The Caddy mill sounds great. What kind of fuel usage would you see? This being a backcountry travel based forum, you know I had to ask! 500/650 is great, but if you are going to get 5-6 mpg, vs 18-20 with a 12 valve, that really has to be a consideration. Unless of course you don't plan on ever being more than 100 miles from a gas station?

You gotta wonder what "The Humungus" would do...

 

[pappawheely]

I had a friend with a caddy motor in his fullsize Blazer. It was so smooth you could not tell it was running and it would pull a house.

 

[superbuickguy]

The Caddy mill sounds great. What kind of fuel usage would you see? This being a backcountry travel based forum, you know I had to ask! 500/650 is great, but if you are going to get 5-6 mpg, vs 18-20 with a 12 valve, that really has to be a consideration. Unless of course you don't plan on ever being more than 100 miles from a gas station?

You gotta wonder what "The Humungus" would do...

you base this on what? have you owned a 500 Caddy in a fullsized truck? Quadrajet on a 500 caddy, and you'd be surprised at how efficient they are - especially in stop and go traffic because they don't have to work at all to get large, heavy vehicles off the line.

 

[redthies]

you base this on what? have you owned a 500 Caddy in a fullsized truck? Quadrajet on a 500 caddy, and you'd be surprised at how efficient they are - especially in stop and go traffic because they don't have to work at all to get large, heavy vehicles off the line.

Slow down there cowboy! I wasn't saying you WERE going to get 5-6 mpg. I was only saying IF that was the numbers, I'd think on it. I've owned big block gas engines (460 Ford with ZF5, and 454 with auto [700R4?]) and the fuel economy varied wildly. The 460 gave me low teens, and the 454 was in the single digits.

I'm not slandering the 500, as I've never owned one. I know it is a great motor, I just don't know what mileage you'd see in a big 4x4 truck. It seems like you DO know what to expect, so please enlighten me.

 

[Woofwagon]

The Caddy mill sounds great. What kind of fuel usage would you see? This being a backcountry travel based forum, you know I had to ask! 500/650 is great, but if you are going to get 5-6 mpg, vs 18-20 with a 12 valve, that really has to be a consideration. Unless of course you don't plan on ever being more than 100 miles from a gas station?

You gotta wonder what "The Humungus" would do...

You would be surprised at what good mileage the 472/500 mill will get. A long time friend of mine here was a Cadillac/Buick mechanic in the 60s and 70s. He regularly saw Sedan Devilles pull down low 20's in combination city/highway. Engine efficiency comes down to two things, brake mean effective pressure (BMEP) and volumetric efficiency (VE). I'm doing research on the right aftermarket cam that will really help the engine. Stock Cadillac cams are almost round, a little more lift and duration will really wake them up yet not sacrifice that wonderful smooth idle.

When cars went to low compression aka low BMEP, mileage took a dump. The lower compression destroyed torque and torque is what is needed to move a vehicle, heavy or light. Diesels have that BMEP in spades as they're running 16:1 and above. A properly tuned Cadillac will have a good compression ratio and will generate so much low end torque to move and then cruise at a low RPM.

I do have a future plan of installing a 4L80E or a built up 700R4 for the overdrive capability. I've also got some tricks up my sleeve to keep the mileage up, like driving with intelligence and some other upgrades.

Historically, a large slow turning gas engine will bring greater torque and mileage than a smaller, higher revving engine of similar horsepower. Remember you need torque to get going and horsepower to go fast. Horsepower is just a measurement of the rate at which torque is produced. A torque mill for a Suburban that is reasonably lightweight is the way to go. I do love the Cummins though. Fantastic engine.

So in reply to your last question, The Humungus - Ruler of the Wasteland, would run a torque monster engine.