M37 engine swap

[M37outlaw]

I am new to this website and have found little informative on this but not enough. I would like to do an engine swap in a dodge m37 with something that i can use the original parts and as little modification as i can but be able to get a little better fuel millage and a more reliable engine for every day driving.

 

[cucvmule]

Welcome, what year is your favorite Ride?

Do you have a running engine now and would want to work on it. Driving or using more will get rid of most problems after things like fuel system is addressed.

Or powerplant swap? 230 cubic inch, how about a 250 Canadian engine? You say fuel mileage, different size tires, axle swap? A little more on the parameters of your expectations. Again Welcome from Missouri.

 

[OutpostM37]

M37outlaw:
There are lots of routes to go in your quest for more mileage and reliability, mostly depending on your wallet and how deep you want to get into it.
Baseline your engine to see where it is at. Compression test, cylinder leak back, oil pressure when hot, lots of things to consider.
You can perform a rebuild of your engine with an over bore of the cylinders.
There are several engines that will bolt up with some radiator location mods. The Canadian 251, or 265 come to mind.
These engines are considered 25" long, as apposed to the 23" 230 US engine.
Some on this site have changed out the Carburetor with good results for drivability and gas mileage.
Remember these vehicles came with 5.83 gearing, and do not like going much over 45mph, 3000 rpm.
Let us know what you find on your engine.

 

[Karl kostman]

M37 as far as reliability goes you do realize that engine was used for almost 35 years in everything from 1 ton Dodge Power Wagons to automobiles and about everything in between with great success! Like was mentioned you need to do some testing to see what condition the engine you have right now is in, outpostM37 had some very good advice there. Then I would look first at the fuel delivery system its old technology and when this truck was built they just gave gas away for free, it just didnt matter but that would be the first place I would look. You can look at the 250 Canadian engine and that will work just fine and JUST A LITTLE TINY BIT better than you 230 currently in the truck, BUT the engine is NOT your biggest problem with what your looking for its the 5.83 gears in the diffs! You could put a blown SBC on laughing gas in the engine bay now you have a 55 mph M37 that will burn the tires to its top speed of 55 mph, waste of time. You can do some things to the 230 to make it very reliable, and how do you know its NOT reliable right now? Then you need to look at the gears, that should be the place you start this project!
Karl

 

[M37outlaw]

I realize they may be reliable engines but mine has no engine and i dont want to put a 230 in it. I know i need to change the gearing. I know how to make it faster and i plan on doing it. The top speed is lower than main street in my town, i just need a different engine that can bolt up to the original transmission and that i can find parts for a litrle easier. I agree outpostM37 has good advice every one who has helped me so far has good advice i just dont have an engine. But thanks to every one that has suggested an engine ive looked into those engines and i think thay will work for what i want but i would like to have a few ideas for engines.

 

[nattieleather]

Why not go for a Chrysler 318 v8? Reliable motor, easy to find parts, will give you road speed.

 

[Sgt Jiggins]

Why not go for a Chrysler 318 v8? Reliable motor, easy to find parts, will give you road speed.

That's exactly what I did and never regretted it. Granted, I'm not a purist/collector that might otherwise turn up their nose at taking this route. But, wow, it really makes for a nice ride. And please, if you go that way, upgrade the brakes first/in parallel. Stopping those things with stock brakes is bad enough, let alone with another 300+/- HP behind 'em.

SJ

 

[Roller]

I used a Dodge 360 with a NV4500 transmission, 5 speed with overdrive. I kept the original brakes and added a booster. Brakes properly adjusted and with the booster will put you through the windshield if stomped on!

Frank

 

[Scott Murphy]

So will a small block Dodge bolt up to the M37 Bell housing or will a V8 manual transmission bell housing bolt up to the transmission?

 

[GT4U]

Ugly truckling had a kit (no longer sold) to do a small block swap along with a guide (with gcode and dimensions to make your own adapter plate). It should have everything for a 318 swap if that is what you are after.

Wayback machine archive:

M37 V8 conversion

 

[Sgt Jiggins]

I have this kit and can't recommend it enough. The problem ugly truckling likely ran into was sitting on inventory while demand waned. If someone is feeling adventurous you might reach out to them to see if they'd make you a one-off (Expensive!) or sell the designs... also Expensive. But they'd probably entertain a reasonable approach rather than just letting it die would be my guess.

 

[Sgt Jiggins]

While I'm thinking about it, I also know a guy...

They may have an M37 that is tricked out with a bunch of uglytruckling mods they'd like to sell. If you're serious about it and not looking to just kick tires I can try to get you in touch with them.

 

[GT4U]

If someone is feeling adventurous you might reach out to them to see if they'd make you a one-off (Expensive!) or sell the designs... also Expensive.

They put up the designs for free, but have since taken them down (they were up for a few years) after redoing the website. If you need the measurements you can use an archived copy of the site.

Here is the transmission adapter plate for reference:

 

[G744]

Over the years since '72, when I started driving my repowered M37 with a 318 V8, I put a lot of miles on it. I came to the realization, high engine/road speed eventually ate up the ring & pinion. It didn't break, it wore out the teeth. I found the same thing a few months later, with a Diesel repower I did. Over the many years and miles (250K) it consumed some 13 sets of R&P gears, some with teeth worn so thin they looked like knives. Yes, they were preloaded right. Some were complete NOS drop-ins when such were available. Yes, I always kept oil in it.

With torque & HP over the stock 80 some-odd they just won't last in the long run. Yes, I drove the piss out of it, pulling trailers and running on the highway at 65+. Indeed, that was my goal; to be able to do just that.

The pix speak for themselves.

 

[Mullaney]

Over the years since '72, when I started driving my repowered M37 with a 318 V8, I put a lot of miles on it. I came to the realization, high engine/road speed eventually ate up the ring & pinion. It didn't break, it wore out the teeth. I found the same thing a few months later, with a Diesel repower I did. Over the many years and miles (250K) it consumed some 13 sets of R&P gears, some with teeth worn so thin they looked like knives. Yes, they were preloaded right. Some were complete NOS drop-ins when such were available. Yes, I always kept oil in it.

With torque & HP over the stock 80 some-odd they just won't last in the long run. Yes, I drove the piss out of it, pulling trailers and running on the highway at 65+. Indeed, that was my goal; to be able to do just that.

The pix speak for themselves.

View attachment 930439View attachment 930440View attachment 930441

.
You know, I can't help but wonder if the metal used for the R&P parts in that truck wasn't a little "suspect". Maybe even they didn't need to last that long because the vehicle wouldn't last that long... Attrition had to be part of the plan back in the day.

Maybe?

 

[John Mc]

That’s roughly a set of gears every 20,000 miles.

I’m curious if others who have done such repowers have had similar results.

I put about 1500 miles on my truck with a 230 engine before replacing it with a rebuilt 251 which I’ve now got about 8000 miles on. The transmission and transfer case were rebuilt during the engine swap, but the differentials are what was in it when I bought it.

Obviously, with those engines I’m not doing high speed driving, but I do spend a fair amount of time between 40 & 50 MPH. I also regularly tow trailers weighing in the 3500 - 6000# range and work in the woods hauling out loads of firewood and sawlogs. I’m very curious to see what things look like when we put the locker in the rear differential in the near future.