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1951 Dodge M37 gets a 351W

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Old 01-30-2014, 09:23 AM
tbone1004 tbone1004 is offline
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1951 Dodge M37 gets a 351W

Hello all
I don't have a Ford truck, I'm a Mopar guy, but one of my Mopars is getting a Ford engine which is why I'm here. I have a 1951 Dodge M37 that is getting a 351W out of a 77 F-250.

Here's the truck-This is sitting in the local VFD Garage where I purchased the vehicle.

Here's the engine-The guys garage that I bought it from

g741.org • View topic - Walter
Here's the build thread

The Truck:
If you read the build thread, I was initially hell bent on making this thing a diesel. I 100% believe that they are the superior engine design to gassers and that in a truck that has a 3 ton curb weight it is the best way to go. Why a gasser? While I can afford to do a proper diesel swap using a 4BD2T, or 4BTA diesel engine, I can't afford to go with a QSB4.5 or the new 5.0 V8 from Cummins. The first two engines are too noisy and borderline scramble your brain when they are idling. The IDI's from Ford are too heavy for a truck that wasn't built to support a 1k+lb engine and are still too rattly at idle. The goal for this truck until I move out of Maine is to have a reliable, fun, cruiser type truck that I can drive to work when it's warm *the top in the pictures is from a '65 chevy and is now no longer part of the truck, so it's topless...* and cruise to the beach and go camping out of it. A gas motor gives me a nice quiet idle, wide RPM band, and respectable power.

The motor: The stock motor is a Mopar Flathead 230 with a whopping 90bhp, and about 190ftlbs of torque with a 3200rpm redline. This engine when it is fully blueprinted, hopped up cam, dual carb intake, headers etc, is capable of an earth shattering 140bhp with 3500rpm redline. This is not enough horsepower to safely drive a 3 ton vehicle on todays roads. It also has a NP420 gearbox where you can't downshift into 3rd until you hit 35mph and the truck slows to between 25-30mph on any normal "hill", of which there are many in Maine...
Mopar 318's are used to be a common swap into the truck, but they don't put out enough power, and the cost/hp of building a 360 as well as finding one in good shape is quite a bit of money. I found the 351W from a guy up north who is moving to Philly and needed to get rid of the motor before the move. It is from a 1977 F250, has 10k on it since it was professionally rebuilt, bored 30 over, has a RV style cam in it and was fully blueprinted. I got the motor for $150 which also helps. Doesn't have a tranny, doesn't have any accessories or a carb, but is otherwise complete.

I'm currently looking for a 2WD ZF to bolt behind this thing. I have to keep the divorced NP200 because the rear axle has an offset diff. I also intend on converting to a serpentine system, ultimately with dual alternators instead of running a battery isolator. Will have one alt running the starter battery with all of the lights, E-fan, gauges, etc and the other will run a deep cycle battery, the hot wire to the trailer plug, electric winch, inverter etc. Seems like a more reliable setup than a single high power alternator and I should have room. This is a long way down the road though. Need a transmission first...

Exhaust is something that I'm not very well versed on and will need some serious advice. The engine has the stock logs on it now which from what I've read should be fine since this won't be rev'd that high, 3100rpm will be the cruising rpm at 55mph with a goal shift point around 3500-4000rpm max. Currently the six has a single exhaust pipe that dumps right where the cab meets the bed. I am thinking that some sort of dual exhaust would make sense and I think to eliminate engine drone I should go with an X-pipe but does anyone have recommendations on pipe diameters and if I should send the exhaust all the way out the back or leave it just ahead of the rear axle on both sides?

EFI is also in the plan for later down the road but want to get it in the truck and running first. Who knows, if I can squeak 15mpg combined out of this setup I might not want to go to diesel until the truck needs a full rebuild again.

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Old 03-11-2014, 08:42 PM
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04KingRanch 04KingRanch is offline
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That is a pretty neat old truck you have there. The only advice I can pass along to you about the whole thing is on the basis of the exhaust, and this is an opinion. I would run the exhaust out the back whenever possible. It always helps to reduce the drone in the cab and under the vehicle. I had a mustang with dumps underneath and I did not care for it, but that is a car that sits a few inches off of the ground and you are doing a truck, so it could be different. It will likely cost a little more to go out the back, but I am a fan of it.

Good luck with your build and keep us up to date with the info and pics!

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Old 03-11-2014, 09:06 PM
tbone1004 tbone1004 is offline
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thanks, I'm still trying to figure out if I'm going to have room to run duals out the back with an X-pipe or if I'll just have room for one to go out the passenger side. I acquired a 4wd ZF5 for it because it was cheap but I'm going to pull a 2wd which is what I really wanted in the first place this weekend so that will help immensely with this project. May be looking at a move in the next few months so won't be doing the swap until the move unfortunately. I need the truck to be driveable to get on and off of the trailer and in/out of the garage etc. Should be a good drivetrain when I'm done.
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Old 06-17-2014, 09:24 PM
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I have the same truck in one of my barns waiting for inspiration and time.

Cool build for you to look through.

M-37 ' Bandit '
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Old 06-18-2014, 08:22 AM
tbone1004 tbone1004 is offline
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I know Paul quite well actually, he's a great guy and great wrencher, makes some pretty tasty syrup too. There is plenty of inspiration out there, just find the time. I actually ended up selling the truck because I had to move to SC for work and don't have storage space for it down here, but the truck ironically ended up about 15 minutes from home, so I'll still get to play with it.
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