engine swap

Bulldog · Post by **Bulldog** » Sun Feb 01, 2009 6:40 am

Hey guys,
My 14yr old son and I are working on his M37 and he has decided to sell his 4bt and buy a 6bt to put in his truck instead. So I was wondering if anyone here has swapped in a 6bt. I know just by looking at her it's going to be a tight squeeze... I was also looking at the frame and it's alot lighter then the frame in my 3500.I plan on boxing the frame but was wondering if I need to lengthening it as well. Will the rest of frame handle the torque of the 6bt?
Thanks,
Bulldog

Tom P · Post by **Tom P** » Sun Feb 01, 2009 10:18 am

It's your truck so do with it whatever you want.
But personally I can't imagine why you would want a 6 BT over a 4 BT?
The 4 BT is a much better choice with plenty of power. The 6 BT would be a waste of engine for what you will gain unless your trying to build a track only "Sled puller". It will also be extremely nose heavy.
Besides the 4 BT fits like a glove compared to the extensive modifications the 6 BT will require.
Just my Opinion.
TGP

Bulldog · Post by **Bulldog** » Sun Feb 01, 2009 11:33 am

Thanks Tom,
I know that the 4BT is a nice little engine and it makes pretty good power. But my son wants to use a 6BT so were going with a 6er. This is not going to be restore more like a resto mod/hot rod. The truck probably will have a sled hooked to it a time or two but it will for sure have a heavy trailer that we use in our business hooked to it. i have to agree with my son on this one the 4BT would be a bit over it's head in this application. So how about it anybody else. Anybody put a 6bt in the m37?
Thanks,
Bulldog

k8icu · Post by **k8icu** » Sun Feb 01, 2009 8:34 pm

I'm planning on putting a 4BT or mayber the Isuzu 4BD1T in my truck. When I started planning out this project I looked at using a 6BT since you can find wrecked dodge trucks with that motor, but decided that the length would be very difficult to squeeze into the truck. Unless you plan on lengthening the nose which would mean adding length to the hood, sides and fenders your going to have to rearrange the fire wall to push that motor back into the cab. You might gain some space with an aluminum radiator, but that's only an inch or two. But with enough time and money you can make just about anything fit.

refit1701 · Post by **refit1701** » Mon Feb 02, 2009 3:05 am

I don't have any advise except to enjoy what you do, it's your son's truck. I've seen some odd mods on M37's but if that's what folks like, more power to them.

Brett · Post by **Brett** » Mon Feb 02, 2009 8:59 am

Just my two cents worth, but maybe you should look at swapping your M37 body onto a cummins powered truck frame. I think you would be miles ahead going this route since with a 6bt and an occasional pulling sled you would obviously want stronger axles frame and trans. I'd start looking for 94-98 Regular cab dodge dually 5spd cummins 4x4. You'd get the 6bt, NV4500(which by now probably has 5th gear fixed), Dana60 up front, Dana70 out back, And a frame that can take the weight and torque. Pop the M's bed and cab on behind the motor, and make up the difference in length with the front sheetmetal, since the six wont fit in there as is anyhow. I like your kid's taste, this should be a fun truck.

Brett

Bulldog · Post by **Bulldog** » Tue Feb 03, 2009 4:52 pm

Thanks guys,
Brett that's some good advice right there! That's exactly what we've been thinking about. I have been looking for a 1st gen for a while now. Comparing the frame of the "37" and any of other trucks it's easy to see that the frame is much weaker in the "37". My son wanted to use as much of his truck as possible but it looks like we'll only be using the body.
Thanks guys,
Bulldog

k8icu · Post by **k8icu** » Wed Feb 04, 2009 6:25 am

Wouldn't a frame swap also be difficult due to the shape of the frames? The newer dodge truck has basically an H frame while the M37s is more A framish. Either way you look at it it's is going to take some frabricating. I agree that for your application putting the M37 body on the newer frame would make more sense. Keep us posted with lots of pictures as you progress.

Post by **Cal_Gary** » Wed Feb 04, 2009 6:54 am

I can't recall ever seeing a single M37 that looked "right" with a different frame under it. The bed and cab appear to sit awkwardly high, with spacer blocks here and there that can be seen from each side. Not my preference, but that's just my 2 cents..
Gary

KenInGA · Post by **KenInGA** » Wed Feb 04, 2009 9:31 am

If you want a truck that can do the heavy pulling your business requires, maybe an M35A2 or M818 will do what you need? I have seen an M37 with a 6TA ( think thats what it was) Cummins in it (out of a UPS-style box truck), but it had Dana 60s under it.

I just don't believe an M37 would quite "fit the bill" for a designated trailer-hauler.

But then again, it is your truck. It'd be pretty neat to see an M37 with a 6bt stuffed in there, and it'd sound purdy, for sure!

Bulldog · Post by **Bulldog** » Sun Feb 08, 2009 12:16 pm

Hey guys,
Well, after alot of measuring and bouncing ideas off each other we have decided to use the m37 frame. I feel that we should be able to reinforce the frame to handle the torque that the 6er will make. I agree that the body of the 37 just wont look right on a later model frame. I'll keep ya posted on out progress. I have some pics to put up and I'll post more as we move along with our project.
See ya
Bulldog

k8icu · Post by **k8icu** » Sun Feb 08, 2009 12:54 pm

Swap the axles too. The original ones just wont be strong enough.

Bulldog · Post by **Bulldog** » Sun Feb 08, 2009 2:22 pm

K8icu
The axles will be going along with the springs,steering and most everything else. We will be building 1 truck out of several. I plan on using late model axles with disc brakes on all 4 corners. This truck is being built for my son so safety is a huge concern.
Bulldog

oldstuff · Post by **oldstuff** » Thu Feb 12, 2009 5:33 pm

I'm really interested in this thread since I'm in the middle of mounting a M37 body onto a 90 Dodge 3/4 ton 4x4 with Cummins 5.9.
The reason That I'm going this way is to have all late model drivetrain with the Cummins. Plus I wanted to avoid cutting into the firewall to make room for the Cummins.
The M37 that I got was a real basket case. Rust holes in the Tailgate, floor and front of box, Floor of cab,and outer sheetmetal of cowling.
Both axels, gastank, carb, aircleaner and other small parts has been scavenged already. The engine is shot
I disagree with the comment that the M37 frame is weaker than a late 3/4 ton. My M37 is a 1963 and it's frame is the same gage ( approx .220") and aproximately the same height and width rails. In fact I'm using the rear crosmember from the M37 in the 90 Dodge frame so that I have all the holes for the bumpers and a hitch. (Exact Same width). The M37 frame tapers steadily from rear to front, while the 90 has a quick neck down at the cowling area.
To start with, I determined where the radiator yoke had to be for the front fenders to be over the wheels. Next I positioned the cab to clear the engine. Since the outer cowl had rust holes I made new cowl pieces 6 inches longer to make room for the longer engine. the firewall was perfect, so now the outer skin will overhag the engine like late 90s Dodges and the hood will still be stock size.
Then figured out how much to cut out of the frame to put the rear fenders over the rear wheels. I took 12 inches out of the frame. The 90 was a standard cab, 8 foot box.
Time to go for now . I'll fill in more details later.
Ray

k8icu · Post by **k8icu** » Thu Feb 12, 2009 6:40 pm

Post Pictures Ray....some of us are visual learners....