M37 Horse Power Increase

[LeoUSA]

Since the M37 engine (78 HP Dodge T245) has a low compression of 7:1, an easy way to increase Horse Power is to increase the compression ratio to 9:1 which should result in adding 15 Horse Power. Removing and milling the head to 9:1 compression ratio is somewhat simple. However, you need to measure the valve lift, allow for clearance, and measure the head combustion camber and simple math tells you how much to mill the head. If anyone is in the Las Vegas NV area I will gladly assist in determining the amount of milling required. The machine shop that I suggest, in the Las Vegas area, to do the milling is Fultz Machine Shop, 2100 W. Bonanza Rd, Las Vegas. Other ways of increasing the M37 Dodge T245 Engine Horse Power aren't worth the effort or $$$. The next step would be to install a Small Block V8; see NOVAK Adapters on the internet.

 

[teletech]

Don't forget that a good multi angle valve job with some light port work will add that much or more power. While boosting compression is a good way to increase efficiency and thus power. I machined mine and wasn't brave enough to go all the way to 9:1. I stopped at about 8.2:1, I got a lot more power from the motor but it's hard to say how much was found where.
You lose so much flow around the valves in the head after going past about 8:1 I wonder if it's really worth pushing to 9:1 and having to fuss over valve clearance.
It used to be fairly easy to get a reground cam to make more power as well, I wonder if anybody still has the profiles to do the work without it costing a fortune?

 

[Roller]

Vintage Power Wagons has a high performance cam listed in their catalog.

Frank

 

[LeoUSA]

Hello "teletech",
Thanks for your input. However, a 3 angle or multi-angle valve and light porting improves horse power just a little bit as compared to increasing the compression ratio. I (M.E. Degree) can supply engineering thermodynamic formulas (Otto Cycle) to prove my point. You can mill the head quite easily as compared to multi-angle valve and porting work. But if you have the engine in a tear down mode, of course by all means, do a multi angle and porting job. A better cam is always OK, but why waste the big $$$. Ancient "L Head" configurations (flat head) are just plain horrible & inefficient combustion process. Raising the compression really works for not much $$$. By the way, increasing from 8:1 to 9:1 is much better.

 

[Bill W]

Just a FYI
Everyone seems to be quoting HP from the civilian 230 manuals.
As per TM 9-1840A the rated Brake horsepower for the 230ci in the M-37/T-245 is 94hp @ 3200rpm, compression ratio is 6.7 to 1.
Also T-245 is the factory sales symbol for the whole truck not just the engine.

 

[T. Highway]

A word of caution on just milling the head for higher compression.

If this is done on an older rebuild of unknown origin and you are not sure if the engine has been Gram Balanced, you run a much higher risk of ventilating the block.

Bert

 

[nattieleather]

Isn't doing all this work on a flat head kind of like putting lipstick on a pig? Even with the added HP in the motor you still have the 5.83 gear ratio at the axles. Short of changing axles and a V8 or diesel motor I believe that trying to make a race horse out of a plow mule is throwing good money after bad.

 

[LeoUSA]

Hello "nattieleather",
I agree, "doing a lot of work" on the M37 flat head engine is putting "lipstick on a pig". Milling the head for higher compression is about the easiest work to do and for not much $$$. As soon as my other 3 projects are completed, I am taking a M37 and removing the complete drive train and replacing the drive train (gas V8 eng, NO diesel eng, trans, trans case, axles - 14 bolt various gear ratios) from a GM/Chevy 2500/3500 Suburban (plenty of donors available - cheap. ) Therefore, the M37 looks classic but a modern drive train with high reliability and being able to drive coast to coast and cruise at 75 mph will be just fine and personally for me, will be worth the effort.

 

[LeoUSA]

Hello Bert (T. Highway),
I would like to clarify "Rotating Balancing and Compression Ratio". Compression Ratio and Balancing the rotating assembly are absolutely NOT related what so ever. By the way, if our bureaucratic government would have upgraded the complete drive train (around early 1960) on the M37 maybe the M37 would have been in use until the late '90s.

 

[Juskatla]

An option for those who want to stay with the a flat head would be to source a CDN 251 and do a swap. This would let you keep the reliability and original design off road ability and a bit more power on the long uphill grades. The 230 has its limitations no matter what you do with it, same as any engine of this vintage. 4BTA or QSB is the holy grail for some who can afford to do it properly but the 318 does the job with less investment.

 

[LeoUSA]

Hello "Juskatla",
The M37 engine of 230 or CDN 250 are almost identical for performance. Here in the USA the absolute so call Holy Grail for engine replacement for the M37 is the Chevy Small Block since 1955. There are and have been hundreds, if not a few thousand, Chevy Small Bolcks (others Chrys/dodge, 318,340,360 and Ford 302, 351) swapped into the M37. Just check with the various manufacturers of adapters. Why would anyone but a Cummins 4BTA into a M37 at 300 - 400 lbs heavier that a Small Block V8 and the performance sucks with stock M37 gears. The top end of the M37 would be reduced from a all day long 55 MPH to about 35 MPH snail pace Top End. The 1100 pound 6 cyl. Cummins QSB (Very Expensive !) would collapse the front end and twist axles and explode transmissions. With the all aluminum Chevy LS V8s in the junkyard at a cheap price that seems to be the best answer above any thing else. By the way, I had a great time cruising (30 ft. twin 250 HP IOs) around the San Juan Islands near your Vancouver BC and Washington USA.

 

[FrankUSMC]

I have been a military vehicle collector since 1976. I have seen, in person, two M37s with V8s, and two M37s with Cummins in them. All the others, have had the good ole flat head 6.
One of the few, Frank USMC RET

 

[LeoUSA]

Hello "FrankUSMC"
I was Shanhai'd into the Army in 1964 where I then became aware of the M37s and drove and rode in them. Most of the remaining M37s do have the ancient archaic or good old flat heads. I have only seen Cummins in the M37 by viewing on the internet. I have helped install 2 small block chevys in M37s. and over the past many years (50), I have seen some (3) Dodge 318 V8 and at least a dozen or more small block chevys. The vendors (NOVAK and others) who sell adapters can tell you the total number of V8 adapters sold for m37s. By the way, I even saw a small block chevy installed in a M37 in Saudi Arabia, 1992. In Saudi Arabia (1992) I saw some wild custom cars but the suburbans (dual AC) and Crown Vics were plentiful.

 

[Juskatla]

I have to disagree that the 230 and 251 are almost the same in performance. I own both in an ex USAF M37 and several CDN M37s. The 230 is gutless for all but flatland driving, while no power house the 251 does make a difference, if there is one at 45MPH. The hills is where you notice much of the difference. As a purist, I like the original look under the hood and have kept all mine in original fit and form. As for the choice of swaps, for a lot of guys, its been the cost and availability that has driven many choices. I have seen many Chevy swaps, Chrysler 318 and 360 swaps and a few Chrysler Nissan diesel implants, some very well done and many 'Bubba" type jobs. Most of us can't or won't ever do a 4BTA or QSB swap, mostly because of cost involved to do it properly. To each his own...

 

[T. Highway]

Hello Bert (T. Highway),
I would like to clarify "Rotating Balancing and Compression Ratio". Compression Ratio and Balancing the rotating assembly are absolutely NOT related what so ever.

Raising the compression ratio will have a direct effect on the engine dynamics. First by increasing the stress applied to all of the reciprocating weight parts (pistons, rods, wrist pins).
Since you already know about rotational balance I'll skip the crankshaft details.

I have to ask you if you ever weighed any NOS rods or pistons for a T-245? Factory parts that were mass produced back then had a target AVERAGE weight that they produced the parts to. Many of the parts suppliers later on didn't stick with this guideline. Different lot numbers will get you vastly different weight components.

My previous post was just a word of caution to my fellow M37 owners, with the hope of preventing a ventilated engine from misinformation / partial explanation.

I know many of our fellow M37 owners out there have seen rebuild tags fastened on their engines when they bought them, and you can't be sure that you don't have a mixed bag of parts installed by someone else. The initial imbalance already in the engine at this point will be magnified by the higher compression, thus causing more vibration which will lead to premature failure.

One saving grace of the T-245 engine is its longer 4.625" stroke length which is very forgiving to engine component imbalance at reduced RPMs.

I will bow out of this thread now because I can read between the lines and know were it will head next.

Bert

 

[Juskatla]

For the benefit of those who don't frequent the G741 site, here is a link to some interesting flathead mod stuff. There are still some 'speed' parts out there but I suspect this is going by the wayside as the experts age out of this hobby. Finding a decent machine shop that still has some old guys in the back who know what these are all about is also becoming a problem in some areas. I am fortunate to have access to a couple but in a few years those guys will also retire and probably close shop.

http://www.g741.org/PHPBB/viewtopic.php?f=3&t=5180

 

[Juskatla]

[ By the way, I had a great time cruising (30 ft. twin 250 HP IOs) around the San Juan Islands near your Vancouver BC and Washington USA.[/QUOTE]

The San Juans are a great place to cruise. I personally like Friday Harbour, Rosario and Roche Harbour, but all the spots are nice to visit. My family had boats since I was very young and living in Victoria, BC we were only a short jump south across the border in those simpler times. These days, my other vehicle is a boat as we have a residence on an island near Nanaimo BC without ferry service. A couple of my M37s are on duty out there. Everyone should boat the Inside Passage at least once in their lives....

 

[Tracer]

Jack Clifford's Performance Products 6=8. Specializes in 4 & 6 cylinder performance parts.

 

[Tuko]

Man my 4BT M37 is a blast to drive, torque is unbelieveable up hills and can do 60 if I wanted to. 5 speed trans helps that along as I still have the stock transfer case and axle gearing. I never drove a M37 with a V8 but I have to believe it's similar minus the torque. And the 4BT isn't much heavier then the stock 230, they weigh in around 725-750 lbs. did I mention it gets 22 mpg?opcorn:

 

[joseph m37]

Just a FYI
Everyone seems to be quoting HP from the civilian 230 manuals.
As per TM 9-1840A the rated Brake horsepower for the 230ci in the M-37/T-245 is 94hp @ 3200rpm, compression ratio is 6.7 to 1.
Also T-245 is the factory sales symbol for the whole truck not just the engine.

wrong, the T designates it was for military use,horsepower was 78hp. G741WAS THE DESIGNATION FOR PARTs assembly