Dodge slant 6 over flathead 6 ????

[1953M-37]

The more I look at my M-37 the more it needs help. I'm thinking of putting a Dodge slant 6 in over the flathead . Has anyone made this swap? And I'm thinking of going from 24 volts to 12 volts. All my wiring is bad . The flathead runs good so let me know what you think..... Miles.....

[8543bob]

GOOD AM, If the flathead runs good, why change it?? You wont get any more speed due to the gear ratio in the diffs. I got my flathead, it runs good, I'm very happy. But whatever U dicide have fun and good luck

[1953M-37]

I'm going to run the flathead for now [Low on Cash] and see how the flathead dose. My M-37 needs so much work that I'm thinking of restoring or updating. It is real funnie when you look a car or truck you have your buyers glasses on but when you get it home it need more than you where looking at. I do have pictures up [miles gleason] and would like to see what some of M-37 owners think I should do. My M-37's birthday is 2-2-1953 and is from the Marine Corp.

[cuz]

No matter which engine you choose the performance limiting factors are the transfer case and the gear ratios of the axles. So to call an engine an upgrade will necessitate doing something to get that engine upgrade's new performance to the road. Once you realize the real cost involved to start an upgrade then it becomes obvious that the upgrade should be able to run efficiently on today's fuels and tomorrow's fuels and should have gearing to get this new power to the road surface. The starting point then should be a new power plant that can survive with today's environment which means a modern gas or diesel engine that can function with some degree of electronics/computer technology. So basically choose your fuel then an engine and running gear parts that will get the performance you want. And finally of course compare those wants and needs to your wallet.

[1953M-37]

Thanks Cuz. The last six word you used are wise. I do not plan to do the drive train swap soon so I have time. I'm thinking of finding a Dodge 4x4 3/4 ton truck and swap the complete drive line to my frame & body. What years would be good to do a swap on ? Miles......

[Josh]

While i am a proponent of drivetrain swaps because the original axles and t case are troublesome, saying that an engine swap alone is worthless is not an accurate statement. A slant 6 has one significant advantage over the flat 6, it revs 2500 rpm higher than the flat 6. This would allow you to run at highway speeds. However, the original drivetrain and the slant 6 will not last long at those rpms. An engine swap alone should be a temporary solution until the rest of the drivetrain can be replaced as well.

[Brett]

Miles,

I would run a compression check on your engine before spending any money on it. These motors will start and run with suprisingly low compression.
i thought mine ran pretty good until I ran a compression check. I had several cylinders near 50 psi. If I remember right there should be at least 110 or so on each cylinder. if your engine needs rebuilding it will cost at least a couple grand. Iits better to find out now so that you know what direction you are going to persue.

For me it wasn't worth spending the money on a motor and truck I was never going to be happy with(stock m37 are a 45-50 mph vehicle). Mine was missing some expensive original parts like the correct carb, and wiring harness. I ended up buying a wrecked 2004 chevy van for $900. I'm now running the 4.8 v8 and 4l80e auto with the van computers and harness. I've got almost 300hp, overdrive, and most importantly a running vehicle for less than what a rebuild was gonna cost. I'm not saying its the way for you to go as it has been a challenge, but I feel it was right for me. Its your truck if you're going to spend a lot of time and money on it, it better be something you're going to be happy with.

Brett

[cuz]

Josh said:

saying that an engine swap alone is worthless is not an accurate statement.

I said it wasn't a cost effective answer and was not a good stand alone upgrade. As you yourself said above. The drivetrain will still need an upgrade after you run it into the ground with those 55/60 MPH freeway jaunts on the new engine.

53M said:

What years would be good to do a swap on ?

You'll get some better responses if you tell us what fuel you want to go with first.

[Josh]

Wes,

I didnt mean my response in arguement to yours, I was just stating a generality.

As Wes pointed out, the fuel choice will dictate alot. I have a Cummins 4 BT in mine now, and wouldnt ever go back to gas. Diesels have their own demons, but in a big, heavy truck like the M, a small6 or big 4 cylinder diesel is the way to go if you can afford it.

The issue with diesel power will be making sure the gearing is right. Reasonably close will work with a gas engine, but it has to be bang on with a diesel for best performance. I put a ZF5 5 speed OD transmission behind mine, with Dana 60 axles, and 4.1:1 differential ratio, 38" michelines, and it purs down the highwy doing 1700 RPm at 60 MPH. I have an exhaust temperature issue I am dealing with, but, I think that is more my fault that Cummins. I put a bigger turbo on the the quest for more power, and I think I got a bit greedy with turbo size... Thats a whole 'nother story though.

My cummins get 18 MPG around town. I havent run a tank through at highway speed due to the aformentioned EGT issue, but once I get that sorted I will post results.

The point of all this? If you can afford it, go diesel. Easier to install, easier to wire, more durable if taken care of, and the low end torque is perfect for moving a truck like this.

you have some options. Cummins 4BT, Perk-a-Pillar (Cat) 3104/3126, Detroit 353, Nissan SD33, Isuzu 4DB1T (4BT clone), among others will all fit. Tehy each have their plusses and minuses.

If you want to do gas, the easiest and most documented would be a smallblock dodge, but, others have done smallblock chevy, small/bigblock ford, even saw a 426 Hemi once.

All depends on how much cutting you want to do. With my Cummins/ZF swap, I had to rebuild the doghouse cover, and the little floor lip behind it from scratch, but that was the only major surgery to sheetmetal. It fits in the frame no issue. As I dont have stock axles, I cant comment on stock axle clearance, but they stockers wouldnt work very well with a 4BT anyway, as the gearing is all wrong. The 4BT will live all day at 1700-2000 RPM. Push them above that and long term durability goes down and fuel consumption goes up.

[1953M-37]

Well as I said the flat head dose run . I'm going to run the flat head till it dies. I want to run a gas motor. I'm thinking of finding a 3/4 ton dodge 4x4 truck and rob the drive line. What year would be a good year truck????? Miles.....

[Josh]

A 1960s dodge would be most technically similar. A 70s would work too, but the NP203 transfer case in them is a gigantic beast.

[Tanner]

If you opt to keep the flathead, you might consider looking into a 5-speed overdrive swap for the 230... that, and some taller rubber could buy you a few more MPH, without killing the NP200.
Another option might be to install a 4.3 GM V6 & matching 2wd 5-speed - fairly inexpensive package. You can have the diffs re-geared to 4.89's, and run the 4BT with ZF 5-speed, but it'll cost more than a gas swap.

Again - what is your intended purpose for the truck, your skill-sets for a swap, and your budget?

'Tanner'

[1953M-37]

I want to make my M-37 in to a driver . I want a gas motor and if I need parts that I could get them easy. This is my wish list... or part....Miles...

[Josh]

What is you level of fabrication skill and tool set?

Are you wanting to stick to a straight mechanical setup, or are you willing to deal with electronics?

Auto or stick?

Budget?

Any specific requirements or limitations? I for example wont use a smallblock GM engine because theyre so common. Do you have any restrictions?

Any power goals or fuel economy requirements?

Estimated miles per year?

Any trailer towing/load hauling?

Minimum top speed? (55, 65, 70)?

Any noise or vibration expectations?

In order to trully be able to make an informed suggestion, we need more info.

[1953M-37]

I don't weld or do body work yet. I'm going to take welding classes and work on my body work skills. A veteran friend want me to keep the old M-37 stock so I'm leaning to stock. I'm a good wrench . I see more work in the truck every time I look at it. So I need to do most of the work my self to keep cost down.I know the M-37 need to be saved as not many are out there . My new money pit....... I want to make the truck in to a sold driver then work on the rust holes. My veteran friend drove the M-37 when he was in the Army.. Miles....