Early 70's Cadillacs and fuel efficiency.

In reply to alfadriver :

To be frank, you don't really NEED to "tune" anything, but you will have to disable any anti-theft (unless you really want to go down the road of swapping a lot of other things in), and if you want a functional check engine light, you'd want to turn off any codes for things that you didn't bring with you with the swap.  In my opinion, there's no reason to not install converters and rear O2 sensors, and making the evap system functional on a GM is not earth-shatteringly difficult either, but if you don't want those things, and you want a functional check engine light so you know if there's a (well, another) problem, you'll have to disable those things.  You can buy HPT and do it yourself (Challenge budget: free), or you can send your computer to any number of people who will do it for you for a set fee, usually $75-150 or so.

The cheap way to swap would be to adapt the engine to the existing TH400 (which would have been a B-O-P pattern and not Chevy).  Really, Caddys tended to be geared TALL, so a smaller engine would not benefit much from having an overdrive in the first place....  why are we putting an overdrive trans in again?

What I build for the Challenge (and Challenge budget) is no where near what I would build for a street driver. 

I’d don’t think there are very many motor swapped cars that have made it to the Challenge I would drive on the streets as-is.   Most of my cars have been street legal (tagged, etc).  I still wouldn’t drive them on the street. 

The only thing a Challenge car has to do is complete 1 drag run and 1 autocross run. 

He said cruiser for Texas highway miles.  I think $5K for the swap is a very reasonable budget (and still much too low to pay someone else to do the work).

Besides, he said $10K was acceptable. 

Nick Comstock said:

SVreX said:

I am assuming “fuel efficiency” is actually about money. 

Regardless of what engine you use, you will be putting it in a 5000 lb vehicle. You are not gonna get 30 mpg. 

Lets assume 20. That’s only 9 mpg more than the average you are expecting.  If fuel remained at $2 per gallon, you will be saving about $0.08 per mile.

If the swap cost you $5000, you will have to drive 60,000 miles before you break even. 

Is the idea that important?

It's not about money. It's the fact that 9 mpgs is obscene for cruising around Texas. It's just extremely wasteful. And if a modern drivetrain swap could double that then yes it's worth it. Even at 10K. Hell if they was an electric swap that had a range of 300 ish miles or so I would have no problems going that route.

I'd like a Coupe DeVille but they started putting pillars behind the windows in 74 I think so I'd be looking at a 71-73.

Ok. I can respect that. 

A Coupe Deville with a Tesla drivetrain would be badass. 

I've been thinking about a swap on my own old Cadillac. It's a '66 with the 427, so it actually gets slightly better economy than the later big engine. Still in the 12-14 mpg range on the highway, though.

Diesel is wrong for this platform. Sure, it's got torque. But it's noisy, and the wrong sort of noise.

The easy button (and one I'm most likely to do) is an LS swap. Trying to maintain the torque levels is hard to judge as the measurements have changed, but I'll bet a 6.0 out of an Escalade would be both appropriate and well torquey enough to get the job done. I rarely find myself into the secondaries on the carb as it is. The question is whether I keep the TH350 or go with something that has a little more overdrive. For my use, I'd probably keep the TH350 so I didn't have to enlarge the trans tunnel.

The perfect swap is a Tesla drivetrain. Absolutely ideal for what the car is.

Agh, it's hard to stay up with the conversation when I can only join in at breaks and lunch. So many things I want to touch on.

Quickly though a couple things I wouldn't want to lose with the swap. Ride quality, quietness and that effortless steering. Quiteness alone would likely deter me from a diesel swap. 

Quickly on the OD trans issue I wouldn't see it as a necessity but a lockup converter probably would be. However if an od trans would be swapped in switching to a shorter rear gear would have to be swapped in.

In reply to Knurled. :

Definitely full cats and evap operational. 

Dammit, when these threads come up, I always seem to feel the need for research and that leads to Craigs Place...

Probably my favorite of the sixty's Caddy coupes. 2.3 large:

https://sfbay.craigslist.org/sby/cto/d/hollister-1967-cadillac-coupe-deville/6768937583.html

Knurled. said:

In reply to alfadriver :

To be frank, you don't really NEED to "tune" anything, but you will have to disable any anti-theft (unless you really want to go down the road of swapping a lot of other things in), and if you want a functional check engine light, you'd want to turn off any codes for things that you didn't bring with you with the swap.  In my opinion, there's no reason to not install converters and rear O2 sensors, and making the evap system functional on a GM is not earth-shatteringly difficult either, but if you don't want those things, and you want a functional check engine light so you know if there's a (well, another) problem, you'll have to disable those things.  You can buy HPT and do it yourself (Challenge budget: free), or you can send your computer to any number of people who will do it for you for a set fee, usually $75-150 or so.

 

The cheap way to swap would be to adapt the engine to the existing TH400 (which would have been a B-O-P pattern and not Chevy).  Really, Caddys tended to be geared TALL, so a smaller engine would not benefit much from having an overdrive in the first place....  why are we putting an overdrive trans in again?

For the most part, that's just keeping more of the donor powertrain, which I'm ok with. 

I'm not sure why the original 3 speed w/o a lock up converter would be better than the original donor 5 or 6 speed with a lock up converter.  And a calibration that is already set up for that transmission.  Less stuff being taken off the donor engine is a good thing.

And taking a smaller dimensional engine and putting into a HUGE hole should be pretty easy- the part that needs the most fabrication are the mounts.  After that, plumbing the cooling system- and, again, perhaps some fabrication so that you are using more donor parts.  Including A/C.  

For those skilled in LS swaps, how much does a complete donor powertrain- from the radiator to the trans output shaft- cost?  One from a large van or pick up.

I'm all for improving something, and the swaps mentioned here would all be cool. But am I the only one that thinks it's funny that somebody who would drive a 20ft long car with fins and enormous chrome bumpers would be concerned about wasteful excess?

I'd definitely use the more modern trans with OD and lockup.  If you don't change to shorter diff gears to get better performance off the line (which still probably won't be terrible, as the modern trans likely has a lower 1st gear), you'd just end up with having a trans that can't / won't (might require tuning changes) use its highest gear until a fairly high road speed.  

If we assume a 2.93 rear diff (stock in a 73 coupe Deville), a 6L80E trans, and 29" tall tires (very close to the stock L78-15 size), 70 mph would give you just a hair over 2000 RPM in 5th gear and just a hair under 1600 in 6th.  So assuming the trans doesn't shift into 6th too much before 55 mph even under light throttle (1250 rpm in 6th, just under 1600 in 5th at 55), you'd be fine with the stock rear end gearing.  First in that trans is just over 4:1, so even with the tall gears it wouldn't be sluggish off the line at all (first would be 11.7:1 overall, compared to 10:1 in first in my Jeep with the same height tires and shorter than stock 4.10 diff gears).  

So realistically, with one of the modern 6 speeds, there's no real need to change the diff gearing, and especially if a few subtle aero improvements can be snuck in, the overall gearing should be pretty darn good for highway cruising (comfort, noise and mpg).  

Half the reason for owning a Cadillac of that vintage is being able to tell everyone you have 500 cubic inches under the hood.      Keep it original, and add a modern intake and some sort of fuel injection if you want to chase mileage.

Mileage wise the complete modern engine will make more mpg and I love the ls engines but I also love the big land yacht engines. The Cadillac engines are a big of a sleeper since they are quiet but makes lots of good old low end torque,good horsepower  and are a very smooth running engine.

It’s an old Cadillac, it’s in Texas. I think it’s probably perfect for it’s environment as is.

Plus, the challenge of making it more fuel efficient by tweaking the original equipment should satisfy the car-guy in you. And the sheer act of the attempt should satisfy the “environmentally friendly” guy in you.

Okay let's take SVreXs  question earlier about if it's worth it. I know we're past that but maybe this will lead to a different type of discussion. As it's not really about the cost dollar wise. 

One gallon of gasoline produces 20 pounds of carbon dioxide correct? 

So for easy math say I drive 1000 miles per year.

At 9 mpg I'm releasing 2,222.22 pounds of CO2 per year. Also in a pre cat era car that doesn't burn each gallon as cleanly as a modern drivetrain will. 

At 20 mpg that drops to 1000 pounds. I think that's well worth the cost of doing it. Because I love big old cars and you just can't get that driving experience in anything modern. But I also don't want to burn the world down while enjoying my big old car either. It's a compromise between my conscience and passion.

In reply to Nick Comstock :

Tesla. 

Or Prius. 

In reply to Nick Comstock :

You won’t make an environmental case for a Cadillac that will convince me. 

There’s lots of other reasons to love ‘em. 

SVreX said:

In reply to Nick Comstock :

You won’t make an environmental case for a Cadillac that will convince me. 

There’s lots of other reasons to love ‘em. 

As far as I can tell, the person who needs to be convinced is Nick.  In the very first post, he mentioned not worrying about the cost, as he's just not wanting to be wasteful.  But at the same time, likes old Caddies, so this is a way to enjoy an old caddy and not have as a big of an impact (however NICK wants to measure that).  

How did this thread go from comparing a stock 472 to an LS in an old Caddy to trying to convince him of getting a prius or tesla???  I don't understand.  Especially trying to convince someone to NOT work on a car....  Makes no sense at all.  Everyone has their own value equation- for sure not mine, as I don't like old Caddies.  But at least address the question he's asking.

My mother’s 2005 Mercury Marquis has all the big car ride quality and gets 20 mpg out of the box with its modular 4.6L V8. 

Plus, it’s got all the power you need when you stomp on it, handles reasonably well, and has safety components that the Caddy can’t ever dream of.  

And, you can buy clean examples all day for under $3K. 

How about a body swap, instead of an engine swap?  Would that scratch your itch?

In reply to alfadriver :

Fair enough. 

The Tesla swap suggestion was a response to his saying budget was not important.  

I simply don’t see many ways to make a Caddy environmentally friendly. 

The answer to the original question is an LS. 

In reply to SVreX :

So you don't see any value in halfing the amount of CO2 I would produce in a year? 

Okay, I do. 

In reply to Nick Comstock :

I think that’s terrific!

In reply to SVreX :

Nice ninja edit. Although condescending. 

Everyone has their reasons for whatever they do. It's a valid reason. 

If you want to make it environmentally friendly then I'd say +1 for EV-swapping it (also helps if you can get cleaner power to charge it with). This could allow you to do way better than cutting CO2 in half, and get way more torque, but of course the initial swap price would be even higher.

In reply to GameboyRMH :

That wasn’t the question, GB.  LOL!