doubleclutchinweasel

You ever get this sorted out???

Puttin' it back the way it came is usually a good plan!

Someone mentioned the Allis-Chalmers "Big Al" engines a few posts back... https://www.donhummertrucking.com/blog/2015/04/17/big-al-is-king

Hope that does it for you. Looks like a lot of bang for the buck, as long as it works. Looks to be fairly simple to install, at least. Let us know!

Sounds like the thermostat is either stuck open or missing. I would almost bet missing. Stick a 180 in it and it will probably be fine for a hobby truck. Actually, I BELIEVE the P1 opened at 155, and the P2 opened at 170. I have all that information somewhere, if I can just find it. http://www.wattstruckcenter.com/store/index.php?route=product/product&path=59_72&product_id=387 Maybe???

Not sure if this helps, but here is the adjustment page from a 2-disc Spicer clutch instruction brochure. It talks about setting the brake, exactly as FJH said, and then adjusting the internal clutch clearance. I had to do this to my old R, after which the clutch and the brake worked perfectly. Whoever put it in had not done this, and I thought I was in need of a new clutch, and I had no brake. But, once properly set up, the thing worked like a charm.

Terry is right on. The coolant t-stat should be a bit below the shutterstat. Mine had a 657GC 225A P1 thermostat. I can't recall if that was a 160 or a 170. But, the shutters controlled the temp from there up to 180-190. I read somewhere that some folks would just run a hotter thermostat if the shutters were stuck open. Some trucks came without shutters, after all. I would think that, with a little work, one should be able to simulate the cooling characteristics of one of the non-shuttered trucks on a truck with stuck shutters. Maybe just put a new 180 thermostat in it??? I'm sure someone here will have some insight into this.

Here is yet another partial list. I pulled these numbers off of some PDFs I have of old Mack brochures. I only listed the ones I can read with some degree of certainty. I have others, but can't read them well enough to trust my eyes. So, this is by no means complete. But, it gives some idea of the variety of engines they used over the years. Incidentally, my 1970 R-611ST had the ENDT-673C, which was rated at 250 HP @ 2,100 and 701 ft-lbs @ 1,600. YEAR MODEL ENGINE C.I.D. FUEL HP @ RPM TORQUE @ RPM ENGINE MAKE 1965 R-401T END-475 475 DIESEL 140 @ 2,400 350 @ 1,300 SCANIA 1965 R-607LT ENDL-673P 672 DIESEL 187 @ 2,100 527 @ 1,400 THERMODYNE 1965 R-607ST END-673P 672 DIESEL 187 @ 2,100 527 @ 1,400 THERMODYNE 1965 R-607T END-673P 672 DIESEL 187 @ 2,100 527 @ 1,400 THERMODYNE 1965 R-609LST ENDL-711 707 DIESEL 211 @ 2,100 602 @ 1,350 THERMODYNE 1965 R-611LST ENDLT-673 672 DIESEL 211 @ 2,100 605 @ 1,500 THERMODYNE 1965 R-609ST END-711 707 DIESEL 211 @ 2,100 602 @ 1,350 THERMODYNE 1965 R-611ST ENDT-673 672 DIESEL 211 @ 2,100 605 @ 1,500 THERMODYNE 1965 R-609T END-707 707 DIESEL 200 @ 2,100 537 @ 1,500 THERMODYNE 1965 R-611T ENDT-673 672 DIESEL 225 @ 2,100 653 @ 1,400-1,600 THERMODYNE 1966 R-401P END-475 475 DIESEL 140 @ 2,400 350 @ 1,300 SCANIA 1966 R-401T END-475 475 DIESEL 140 @ 2,400 350 @ 1,300 SCANIA 1966 R-403S END-465C 464 DIESEL 155 @ 2,600 350 @ 1,600 THERMODYNE 1966 R-403X END-465C 464 DIESEL 155 @ 2,600 350 @ 1,600 THERMODYNE 1966 R-609LT ENDL-711 707 DIESEL 211 @ 2,100 602 @ 1,350 THERMODYNE 1966 R-611LT ENDLT-673 672 DIESEL 211 @ 2,100 605 @ 1,500 THERMODYNE 1966 R-709S ENDL-711 707 DIESEL 211 @ 2,100 602 @ 1,350 THERMODYNE 1966 R-711S ENDLT-673 672 DIESEL 225 @ 2,100 653 @ 1,500 THERMODYNE 1966 R-731ST NH-220 743 DIESEL 220 @ 2,100 606 @ 1,600 CUMMINS 1966 R-737ST NHC-250 855 DIESEL 250 @ 2,100 685 @ 1,500 CUMMINS 1967 R-685LT ENDT-675 672 DIESEL 237 @ ? 906 @ 1,200 MAXIDYNE 1967 R-685ST ENDT-675 672 DIESEL 237 @ ? 906 @ 1,200 MAXIDYNE 1970 R-401T END-475 475 DIESEL 140 @ 2,400 350 @ 1,300 SCANIA 1970 R-487P ENDT-475 475 DIESEL 190 @ 2,400 450 @ 1,600 SCANIA 1970 R-487P-T ENDT-475 475 DIESEL 190 @ 2,400 450 @ 1,600 SCANIA 1970 R-607LT ENDL-673C 672 DIESEL 180 @ 2,100 540 @ 1,400 THERMODYNE 1970 R-607ST END-673E 672 DIESEL 180 @ 2,100 540 @ 1,400 THERMODYNE 1970 R-607T END-673E 672 DIESEL 180 @ 2,100 540 @ 1,400 THERMODYNE 1971 R-491S V8-210 504 DIESEL 210 @ 3,300 387 @ 1,900 CUMMINS 1972 R-487P-T ENDT-475 475 DIESEL 190 @ 2,400 470 @ 1,500 SCANIA 1972 R-611ST ENDT-673 672 DIESEL 225 @ 2,100 653 @ 1,500 THERMODYNE 1974 R-611ST ENDT-673 672 DIESEL 225 @ 2,100 653 @ 1,500 THERMODYNE 1976 R-607T END-673E 672 DIESEL 180 @ 2,100 540 @ 1,400 THERMODYNE

Or this one...

Check this out... https://www.macktrucks.com/-/media/files/museum/model-production-numbers-1905-2000.pdf

Is there any way there could be an air pressure switch shutting off the fuel supply? Not sure if that would be intentional or accidental. But, it sure sounds like the two are connected, doesn't it? Maybe check voltage at a fuel shutoff solenoid (I am assuming there is one). Sounds like a good one for one of the Mack technicians to answer...if any of them are still around! This is a little (lot!) out of my field!

Welcome to the jungle! When you say "won't start", what exactly do you mean? Will it turn over okay but not light? Will it not turn over at all? Does it turn, but turn slowly? The more details, the easier it will be for one of the guys to zero in on it.

I remember that the long ears were a little harder on the palms when opening the hood on an R!

Wow! That's way too early for my limited knowledge! Hopefully, one of the guys who is more into the older stuff can help. Welcome aboard, anyway!

Exactly. Keep the Maxidyne up in the 1800-2100 RPM range, and it is well off its torque peak, which was down around 1200 RPM. It's only when the RPMs start to fall that the increased torque of the Maxi becomes prevalent. And, like Terry said, if it's just a toy, and isn't too heavy, it probably won't be an issue anyway. But, if you're gonna work it, just keep the RPMs up in the normal Thermodyne operating range, and drive is sensibly, and it should be fine. That being said, the 676 still is a monster, torque-wise. Look at the graph below (for a 285 HP version). Even at 1800 RPM, it's still got 825 ft-lbs on tap. That was more than most transmissions of the day were rated for. Hence the triple-countershaft Maxitorques. I wouldn't jerk it too hard! I have heard of several folks running a 237 in front of these boxes, and that works very well if you stay out of the fat part of the torque curve.

Or here...

I think the U and DM were the same exact cab. 'Couse, I never swapped one out, though.

Start here...

18-speed Quadruplex. Double over. Adds the lo-lo range. Still has all the Bulldog Cool of having 2 sticks. Real Macks need 2 sticks. Not necessarily if you're gonna work them, but definitely if you play with them! Loved the RoadRanger that came in mine, although it was direct (no over). But, hated not having both sticks... Okay, so I have a little masochist in me!

Not sure if this helps anything, but the range shift on the 15-speed Fuller I had did not want to shift when I first started the truck. I had to sit there in neutral and flip the hi-lo several times to get it to shift. Once it shifted, it was good for the rest of the day, even if it was cut off and restarted. This was a lot more noticeable when it was cold, and nowhere near as pronounced when it was hot. I believe I had a slave valve gummed up, preventing proper air flow to the shift cylinder. That truck had a little oil in the air system, and I believe that oil was causing the slave valve to be stubborn. These air-shifted puppies can be picky about clean/dry air.

Ah! Got ya.

Maybe 24" circumference (8" diameter)??? Is that a single-chamber or a split tank?

One gorgeous R........