engine for towing with m37

[bobcat1/178th]

Have a 53 M37....looking to find a larger engine that still is a flathead but has the power to tow a M151 on a small trailer.......heard of the 251 and 265 but how complicated is it to put in and will they have the power needed..? I would prefer to keep the original GI look of the flatheads......

[Jess]

The Canadian M37s have 251s. A bit longer, so front motor mount is a bit further forward. Rad mounting is a bit different as well. You might also need to confirm the clutch and transmission input shaft sizes, as they can differ. There are some members here with more expertise and those that have made the swaps who should chime in. RMS can fill in the details for you when he reads this post.
Edit: There is significant power improvement but depending what you expect, may not be enough. Top speed is pretty much the same on stock, but as noted in the next post RMS has experience with both the 251 and the 265 plus modifications.
Jess

[52 M-42]

The Canadian guys know all about the bigger flat head 6 cyl. engines. Robyn (RMS) has done a lot of work / engineering on improving the engines' performance and would be a great help to you.

Hopefully they will see your thread and be along shortly........

Ah, I see they have started showing up already.

[RMS]

if you want to stay with a flat head/L head the 265 is the way to go. there is a bigger flatty but it has something like a 32" long head. it could work but your rad would need to be mounted on the outside of the grill. 251s/265s can be found in threshers, stationary pumps......best to find a 265 with full flow 1954 and later.
links: http://www.g741.org/PHPBB/viewtopic.php ... &hilit=265
http://www.g741.org/PHPBB/viewtopic.php ... 265#p40362

the only hard part about fitting a 251/265 in an American truck is the lack of captured nuts on the front x member for the front mount. the rad and shroud are easily modified if you can drill and weld. if you move on it I can post detailed pics of the changes. there are also differences in the hood. i believe an American hood will work with a Canadian rad but a Canadian hood will not work with the American forward shroud(?)(the stamped sheet metal between the rad and grill). the 230 trans, bell housing, flywheel, clutch will all bolt to a 251/265 however the clutch on the 251 is bigger @ 11in (I think a chev 350 12in diaphragm clutch cover and spinner(custom depending on trans) will work on a re drilled stock flywheel. the benefits would be easier disengagement, less stress and wear on the fork, bushings, rods, left leg and most important less thrust on the crank ). Your 230 carb will have to be re jetted or pick up an adapter and webber from vpw. a high comp head/milling will add jam for cheep.

will they have the power needed..?

like beauty it's in the eye of the beholder.

im running a 251 with a stock carter, points, a milled down car head around 8to1 and 1100r16s with 4.89s. the only time i find I dont have the power is when Im loaded flying on the hwy and get to a tall bridge or a big hill and the rpms drop off and I fall from the power band and end up @ max torque. its not often I need 3rd but ever once in a while some jerk will hit their brakes at the base and I end up lugging in 3rd

[bobcat1/178th]

Ok,,,,outstanding.....I will keep looking for a larger motor......thanks for the info......ill get back for details if I find one......

[bobcat1/178th]

Anyone know why we (us army) stayed with the 230 instead of going to the 251 that Canadians used...?

[RMS]

canadian cars and trucks came with a "long block". the 230 (short) was well established in the American civilian market since the late 30s and was used heavily in ww2. it would have been very expensive to retool for the long block and chrysler was already working on the hemi...... why didn't we get 271 hemie in the 37? I gess if that was the case many of us could not afford a m37 if there would be any left.

for a easy way to confirm what it is, is to bring a tape and a piece of wire to shove down the pipe plug hole @ no6. a 251 has a 4 1/2 in stroke the 265 a 4 3/4in. your 230 has a 23in long head were as the 218/236/251/265 have a 25in head. manifolds are longer as well so if you can be choosy don't buy the one with the updraft zenith. also pull a valve cover and look at the size of the valve stems on exhaust to confirm if they are sodium filled. standard Plymouth and DeSoto car motors don't have sodium filled valves and are prone to tulip and drag out seats.

[m37jarhead]

Have a 53 M37....looking to find a larger engine that still is a flathead but has the power to tow a M151 on a small trailer.......heard of the 251 and 265 but how complicated is it to put in and will they have the power needed..? I would prefer to keep the original GI look of the flatheads......

Bobcat:
M37's, with their low gearing are known to be able to pull houses off their foundation.
The military pulled M 101 trailers full to capacity and maximum weight with M37's. Probably
as much weight or more than an M151 on trailer. After all, it's not dead weight like pulling stumps.

With this in mind my thoughts are:
1. why do you want more power?
2. Have you tried towing the M151 with your current engine setup?
3. I have an M151A2 that I flat tow. I think I could tow it with a VW Beetle. Stopping might be a problem.

Larger engines might give you quicker 0 to 40 mph times but that may be marginal at best.
As mentioned above in previous posts, a bigger engine will not increase top speed because of the gearing.
You're a flatlander with no appreciable elevation changes like the mountains many of us have
to deal with.

I think a bigger concern is how to make your towing package STOP. M37's are notorius for having poor
braking ability. This would be a major concern if your trailer does not have electric or hydralic brakes.

All of the above comments and more need to be considered before you invest copius amounts of $$$
and time/labor before an engine swap. The bottom line here is what do you want, what do you need,
what can you afford, and what kind of results are you expecting?

Let us all know what you decide.
Jerry Bubolz
Gilbert, AZ.

[JimC]

I agree about the crappy braking, but a big, high revving engine with stock gearing will get you from 0 to 100 mph a whole lot quicker than the flatty will, and with a lot less gear shifting. Mine tops out at a little over 111 mph. I put a big V8 in mine almost 50 years ago and have never regretted it. My average fuel mileage did decrease by 2 mpg, but it was worth it.

[RMS]

a few guys around me complained about the brakes on their m37s. I said "a major adjustment would help" and I told them "if I spike my brakes I can lock my tires at any speed". they said "your running 900r16 ndts try stopping my 1100r16 xls or 41in tall goat tires.... you could never lock them up." they were wrong. a four hour full major/minor with the shoes set to lead and trail had the 41in goats @ 22psi locking up when spiked. yes they are harder to operate than any toyota or honda with vacuum boost but with proper adjustment the m37 should pull up quicker and easier than a stalled out chev with hydro boost.
my m37 pulling a <3500lb trailer with 2200lbs of Datsun without electric brakes hooked up stopped better than the other guys m37s with poor adjustment.
if the arrows on your cams are pointing directly at each other you need a major adjustment.

[8543bob]

GOOD MORNING,
Its been awhile since I have been on this site, but anyhow; I rebuilt my M 37's engine about 6 months after
sandy hit my community. The M had water in all the wrong places. She laid for awhile till I got my house liveable, then I did an engine rebuild; I found the top ring on all the pistons were broken, and if you laid a straight edge over the head, you could slide a piece of paper under it. After the rebuild I can tow my full (400 gals) water buffalo without a problem, over bridges and up grades. I don't know what more power you might need. I would look to a properly running engine.
BOB

[justindearb]

I have some good 251 performance info for you! I just finished building up a IND 251 last spring and I put it I my truck and the results were astounding compared to the 230!! I also needed more power but I wanted to stay with a flathead so what I ended up doing was getting a ind 251 (with a 8lug flywheel with 10 and 11' pp bolt patterns) and full flow oil filtration, I first balanced the rotating assembly and a full rebuild then I sent to camshaft out to delta camshaft in Tacoma Washington to have the cam reground to a 400m grind which is what they recommended for my application good tq and HP gain at a lower rpm max 4500, then I shaved the head .060 to bump compression, then I got civilian manifolds (higher rise intake and four bolt exhaust flange) then gasket match ported the maniflolds and block for good flow, it has hardened valve seats, sodium filled exhaust valves, I have the stock M37 carb on it with the governor removed and a good flowing exhaust

THE RESULTS
the truck is amazing now, sooooo much more power easily will tow your trailer, there is a hill in my town about 1.5 miles long and 8-10% grade with the old 230 engine I would hit the hill screaming at 45 at the bottom and by the top I would be still in 4th gear but only lugging at 20 mph now with the 251 I hit the hill at 45 and at the top Iam doing 43 that is a huge improvement my truck now even with the 5.83 gears will comfortably do 50-53 without the engine sounding like it is going to come unglued the tires are only 34" iam going to get some 38-39" tires then I figure I can cruze nice at 55-58, I would highly recommend the 251 or 265 swap the 265 is the same except it has a 1/4" more stroke which is great for tq but if not balanced you may have some revving issues over 2500, I figure that my engine is about 135 HP and 245TQ is my guess and I don't even have a header or 2 carbs so there is still a lot of room for improvement in the future I hope this helps! let me know I would be glad to help if you have any questions!

[justindearb]

251

[justindearb]

had to make this air filter setup because with the new higher rise intake the carb elbow hit the hood, plus this is way better filtration than the old oil bath

[Kaegi]

had to make this air filter setup because with the new higher rise intake the carb elbow hit the hood, plus this is way better filtration than the old oil bath

must be sweet to drive with that 251! nothing like new and improved. the stock cams are made for 70 octane to now its set up for todays 89. the only disadvantage on the paper filter is now you don't have the elbow which is a protection against filling engine with water in fording situation. I read an SAE comparison study about oil bath v. paper and they both scored about the same. the oil bath will remove the finer particles than the paper but the paper can flow slightly more. so each has trade offs. same with the oil filter testing they did the full flow removes larger particles and the bypass will remove finer particle and will take the acidity out of the oil. on mopar truck 361 and 413-4 engines they had both bypass and full flow oil filtration. that would be ideal.