237 Thermodyne

[Diesel Brad]

How long did Mack build the 237 hp Thermodyne - were they all 672 cid ? Any history would be appreciated. How much hp did they max out at ?

[HeyCharger]

If I may just jump on this thread, where are the engine serial numbers stamped on these engines?

Is this engine also referred to as ENDT-675?

Thanks. Rod.

[HK Trucking]

The 237 was a Maxidyne, not a thermodyne.

Yes it was known as the ENDT 675.

It was 672 Cu.In.

The numbers are stamped in the block, just ahead of the inj. pump, on that curved area right where the timing case cover bolts on, unless it was originally in a cabover truck, then the numbers could be on the rear of the block, just below the head gasket.

[HeyCharger]

The 237 was a Maxidyne, not a thermodyne.

Yes it was known as the ENDT 675.

It was 672 Cu.In.

The numbers are stamped in the block, just ahead of the inj. pump, on that curved area right where the timing case cover bolts on, unless it was originally in a cabover truck, then the numbers could be on the rear of the block, just below the head gasket.

So is the block similar to my 673P?

Are any parts interchangable, ie air starter, injection pump, water pump etc?

Thanks again. Rod.

[HK Trucking]

Sounds like you're considering swapping a 237 into your B model to replace your 673?

It's basically a bolt in swap, everythings pretty much the same, you have to use the water pump & housing from the 673 cause its shorter. Other than that just make new intake & exhaust piping to accomodate the turbo.

If your truck has the lower right side mounted starter, you'll have to swap your original bellhousing onto the 237.

Good luck, you'll enjoy that 237 in your B model.

[HeyCharger]

Hi HK, Yes, last weekend I blew a big end bearing which did considerable damage to the crankshaft and there are metal filings everywhere.

Quite a few people have suggested that I not waste time on the 673, but replace it with a 237 for lots of reasons.

I have been reading with interest Jeffs story on "My B61 Project, finally the engine is in"

My air starter current setup in on the left hand side (your drivers side).

You saw the piccy I posted. Initially I was towed by a Western Star and then this Ford towed me home.

Oh well at least they are all home now.

Regarding engine numbers, can you provide me with a typical 237 engine number, or how do I know the engine is in fact a 237.

Thanks. Rod.

[HK Trucking]

On a 237 it would be Stamped "ENDT675" with some other numbers following that indicating the serial #.

On engines sold in the US there is also a tin ID plate attached to the side of the block, directly above the inj pump, behind where the high pressure lines are. This plate indicates what year the engine was certified to meet US emission standards, and if I remember correctly also has horsepower ratings on it. Not sure if engines on your side of the pond would have that ID plate. Also (assuming no one has substituted different valve covers) there's a nameplte on the top of the valve covers that would say

"Maxidyne Diesel". (On your 673 the valve cover nameplate would indicate "Thermodyne Diesel")

Looking at some old literature here, the Horsepower on your 673 was 180, Vs the 237 you'll have now, but the real difference is the torque which is501 lbs.ft. for the 673 Vs 906 lbs. ft. for the 675.

There has been some discussion here in the past as to whether the single countershaft transmissions TR, TRD, TRT, & TRQ 72 , 720, & 7220 will handle the increased torque of a maxidyne engine.

I have swapped a 237 into a truck with a TRQ7220 quadruplex, and have swapped a ENDT 676 (285) into another truck with a TRQ 7220, and the transmissions handled it just fine. It's just like anything else, if it's driven respectably & sensibly it'll last forever, but if someone abuses it, it'll break.

After giving this some more thought, your B model almost certainly has the push type clutch, whether it be a single disc or double disc type. All of the Endt 675 237 HP motors I've seen have the pull type double disc clutch (with the exception of the few that had that assinine Dynamax wet type clutch), however just use the flywheel & clutch from the 673, it'll bolt right up to the 675.

While it's apart check the clutch disc or discs for any cracking in the center near the hub area, replace if questionable, I've seen quite a few of those tear the center out, that would be a bummer to have that happen right after the transplant.

Also, if using the original bellhousing that comes with the 237, make very certain that the bolts holding the housing to the engine block are tight. These had a way of coming loose at times, and the resulting flex between engine & trans is what causes the clutch discs to crack around the hub.

If changing to your old bellhousing, the bellhousing should be dial indicated to ensure it is concentric with the crankshaft, as misalignment here can also cause the discs to crack.

During your junkyard engine search you may also run across an ENDT 673 which looks externally to be identical to the ENDT 675, except that the ENDT673 was usually bluish green, and the 675 was gold, copper colored or for the later ones, grey.

The ENDT 673 would also be an excellent choice for a re power, these were rated at either 225 or 250 horsepower & 653 or 700 lbs. ft. torque depending on whether it's an ENDT 673 B or C.

I'm digging way back into my memory and my old literature for this, hope it helps & if you have any other questions I'll try to answer them

Herb

[theakerstwo]

On a 237 it would be Stamped "ENDT675" with some other numbers following that indicating the serial #.

On engines sold in the US there is also a tin ID plate attached to the side of the block, directly above the inj pump, behind where the high pressure lines are. This plate indicates what year the engine was certified to meet US emission standards, and if I remember correctly also has horsepower ratings on it. Not sure if engines on your side of the pond would have that ID plate. Also (assuming no one has substituted different valve covers) there's a nameplte on the top of the valve covers that would say

"Maxidyne Diesel". (On your 673 the valve cover nameplate would indicate "Thermodyne Diesel")

Looking at some old literature here, the Horsepower on your 673 was 180, Vs the 237 you'll have now, but the real difference is the torque which is501 lbs.ft. for the 673 Vs 906 lbs. ft. for the 675.

There has been some discussion here in the past as to whether the single countershaft transmissions TR, TRD, TRT, & TRQ 72 , 720, & 7220 will handle the increased torque of a maxidyne engine.

I have swapped a 237 into a truck with a TRQ7220 quadruplex, and have swapped a ENDT 676 (285) into another truck with a TRQ 7220, and the transmissions handled it just fine. It's just like anything else, if it's driven respectably & sensibly it'll last forever, but if someone abuses it, it'll break.

After giving this some more thought, your B model almost certainly has the push type clutch, whether it be a single disc or double disc type. All of the Endt 675 237 HP motors I've seen have the pull type double disc clutch (with the exception of the few that had that assinine Dynamax wet type clutch), however just use the flywheel & clutch from the 673, it'll bolt right up to the 675.

While it's apart check the clutch disc or discs for any cracking in the center near the hub area, replace if questionable, I've seen quite a few of those tear the center out, that would be a bummer to have that happen right after the transplant.

Also, if using the original bellhousing that comes with the 237, make very certain that the bolts holding the housing to the engine block are tight. These had a way of coming loose at times, and the resulting flex between engine & trans is what causes the clutch discs to crack around the hub.

If changing to your old bellhousing, the bellhousing should be dial indicated to ensure it is concentric with the crankshaft, as misalignment here can also cause the discs to crack.

During your junkyard engine search you may also run across an ENDT 673 which looks externally to be identical to the ENDT 675, except that the ENDT673 was usually bluish green, and the 675 was gold, copper colored or for the later ones, grey.

The ENDT 673 would also be an excellent choice for a re power, these were rated at either 225 or 250 horsepower & 653 or 700 lbs. ft. torque depending on whether it's an ENDT 673 B or C.

I'm digging way back into my memory and my old literature for this, hope it helps & if you have any other questions I'll try to answer them

Herb

The 673p was a older block and crank than the maxidyne or the endt673a,b,c engine The end673p was the engine that had two intake manifoilds for better air flow and was rated at 187hp and did not have piston oil cooler nozzles and the end673a,b,c, was same block and crank as the maxadyn but I think the sealing surface on the liners was smooth like the end673.I worked for mack when the b modle was still in production and sure like working on then and still work on macks Glenn Akers

[HK Trucking]

Glenn, now that You mentioned head gaskets, Didn't the ENDT 673 A & B have the old type head gaskets & the C had the fire ring set up, just like the ENDT 675 maxidyne?

It's been over 20 years since I've had an ENDT 673 apart, but I remember working on a B without fire rings, and a C that did have fire rings.

Herb

[scott]

Sounds like you're considering swapping a 237 into your B model to replace your 673?

It's basically a bolt in swap, everythings pretty much the same, you have to use the water pump & housing from the 673 cause its shorter. Other than that just make new intake & exhaust piping to accomodate the turbo.

If your truck has the lower right side mounted starter, you'll have to swap your original bellhousing onto the 237.

Good luck, you'll enjoy that 237 in your B model.

save the damper hub from the original 673. it is also shorter and needed to clear the radiator. scott

[theakerstwo]

Glenn, now that You mentioned head gaskets, Didn't the ENDT 673 A & B have the old type head gaskets & the C had the fire ring set up, just like the ENDT 675 maxidyne?

It's been over 20 years since I've had an ENDT 673 apart, but I remember working on a B without fire rings, and a C that did have fire rings.

Herb

I think the endt 237hp maxidyn was the first that had the new sealing bead on the liner but same block.It has been 25years since I have been into a c but may be wrong. Then in the old block before the maxidyn there was two blcks and one had a full flow/ bypass oil filter and the older one before the which was a 170hp used a by/pass luber finner oil filter only It was the engine that did not have a coolant regulator or thermostat.

[Joe Cummings]

All the C engines I have worked on had fire ring liners in them. That's not to say they were all built that way originaly. The fire ring liners and gaskets could be used with any 672 inch block with 20 stud heads, as long as you cut the heads for them. In fact I was told that you could use the fire rings in an 18 stud engine if you cut the gasket, but I have never confirmed this.

As far as the clutch being a pull type in all Maxidynes. I had both a 68 R600 and a 69 DM600 both original Maxidyne trucks that had push type clutches in them. I think they were called CL-50. they had a 2" spline and the trans was somewhat different. The clutch brake wasn't on the spline, it was on the bottom countershaft as I remember.

[jackson.hancock.@gmail.com]

So can you fit a maxidyne into a b model that has a quad tri or duplex transmission

 

[davehummell]

I am in the middle of doing that right now. mack is like the old chevy motors. I just swapped bellhousing and flywheel clutch right over. You have to use the old style front hub I am using the fan and pulleys and front motor mount off the old engine it goes right on my newer engine. do your self a favor and remove the crossmember the front motor mount sets on and the radiator lower crossmember I was able to just run the engine right out straight with my forklift very nice. For now I am going to run my duplex and see how it works out my eng is 260 hp. so I think I wave enough gears. I was working by myself so I removed the fenders off first if I knew how easy they came off I would of pulled the right one off when I changed the injection pump and air compressor. Good luck

[Freightrain]

Put a 237 in front of my triplex.  Drives real nice.  Don't lug it down below about 1400 rpm, or the transmission will remind you NOT to.  It will start to thump and it won't put up with that for very long.

Use the 673 water pump and balancer.  the rest is a simple bolt in.  I used my single disc clutch.

[Frankinstien tractor]

I know this is a long shot but would anybody know the water part part number off a 237 , build date March 74 , or where to possibly get one .

Thanks for your time 

[Freightrain]

I can't help, but someone will be along and tell you.  Welcome to the forums.

[j hancock]

2 hours ago, Frankinstien tractor said:

I know this is a long shot but would anybody know the water part part number off a 237  

Mack 316GC1184.  Haldex had a listing for them RW2001 and RW2001X for a reman.  Listing also included RW2006X if a fan clutch is being used.

[Frankinstien tractor]

I know this is a long shot but would anybody know the water part part number off a 237 , build date March 74 , or where to possibly get one .

Thanks for your time

On 7/31/2020 at 5:26 PM, j hancock said:

Mack 316GC1184.  Haldex had a listing for them RW2001 and RW2001X for a reman.  Listing also included RW2006X if a fan clutch is being 

I cant possibly thankyou enough for your time and effort , I'll have to try and post some pictures of the old girl for you guys to laugh at .

[alex g]

7 hours ago, Frankinstien tractor said:

I know this is a long shot but would anybody know the water part part number off a 237 , build date March 74 , or where to possibly get one .

Thanks for your time

I cant possibly thankyou enough for your time and effort , I'll have to try and post some pictures of the old girl for you guys to laugh at .

I'll take a look I might have a nos water pump here

[Frankinstien tractor]

On 8/2/2020 at 6:31 AM, alex g said:

I'll take a look I might have a nos water pump here

If you do let me know , I am in edmonton .

 

[alex g]

Pm sent

[KKERGALL]

Did you find a water pump? Have some if needed. Rich

[Frankinstien tractor]

Just calling around today