Cummins 275 HP ISB

Bob Gil · July 26, 2008, 06:32:05 PM

Just wondering would a 275 Hp ISB be a reasonable replacement for the 6V53 in this bus I have?

I am not sure if I have a left hand rotation engine or how it works. I was just visiting my dad and I have a NEW ISB that has never been installed in any thing that i need to do some ting with. I was going to put it in a 1964 B model Mack but I have not gotten around to that project yet.

Am I crazy for thinking about it?

Bob

TomC · July 26, 2008, 06:46:17 PM

The only real problem will be the length difference between the Detroit 6V and the inline Cummins 6. Are you sure it is a ISB? 275hp sounds a bit high for it-might it be a ISC instead? I know they do make up to a 325hp ISB, but that's a very recent horsepower rating. The ISB at 275hp will produce 660lb/ft torque, if it is an ISC it will produce 800lb/ft torque. Your 6V-53 if it has 55 injectors will produce 210hp @2800rpm with 440lb/ft torque at 1800rpm. Either way, alot more power. I would do it. Good Luck, TomC

Bob Gil · July 26, 2008, 06:56:42 PM

I am sure it was a 275 it was set up for a piece of emergency equipment but never got installed back in 2002.

I will have to get the ruler out and see how much diference there is in the lenght. I don't think there is as much as there would be with a bigger (say 350 or bigger engine).

Would the ratoation be the same? I don't think the 300 rpms would be a big problem if I were to go to an over drive transmission.

NJT5047 · July 26, 2008, 09:16:32 PM

If your engine is a "T" drive...it's a right-handed engine and the ISB would work. Bell housing may need to be changed in order to match your transmission. If the ISB has a bell housing. You'll need the correct category bell housing to match your trans.
As I recall, you coach is a "T" drive. Any truck engine you can shoehorn in will work. Go for it!
If your engine sits facing fore and aft, you have a RH truck styled engine.
If it's transverse (as in GM) it's a LH rotation. LH engines sit crossways in the coach.
Your transmission will work. You may not squeeze the last MPG out of the engine, but if you amortize the cost of an OD trans, you'll be years to benefit from your trans investment.
Another thing to consider is that with 275 HP you don't really need an OD transmission.
It would be nice, but?
When measuring, consider the length of your driveshaft as you may be able to move the transmission foward if necessary. This is an issue on MCIs with overhead squirrel cage blowers, but maybe not so much if your radiator is side mounted.
Do you have access to the intercooler and and electrical components? You may need a donor?
If you could find a wreck or out of service truck with an ISB, that would be invaluable for all the bits you'll need to complete the conversion.

HTH, JR

TomC · July 26, 2008, 09:34:10 PM

What transmission do you have-make, model and speeds? Good Luck,TomC

TomC · July 27, 2008, 09:57:09 AM

Bob if you have the MT643, you could rebuild your 6V-53 into a turbo motor (18:1 compression compared to the 21:1 compression on a natural) with a custom air to air intercooler. 350-400hp is not unheard of from these engines. The US military has some vehicles specifically designed for these engines, so they are secretly still being made. Personally a 300-325hp would be a good fit. Exchanging to a Cummins 275hp will be ALOT of work. Good Luck, TomC

Bob Gil · July 27, 2008, 06:08:49 PM

Not sure about rebuilding the 6-53 cheaper to install the cummins I would think.

I am not sure of the trany but it is a 6 speed alaison.

Since the dash is all digital and I have the computer and all the sencors already munted on the engine it might not be too hard to do.

It's set up for electronic gas peddle too. I could do away with the sorry linkage that is there now.

The radaitor is mounted to the side too.

I will have to see how the 6-53 runs when I get it going.

I might be dreaming too soon.

TomC · July 28, 2008, 09:14:18 AM

While the 6spd Allison on your bus sound great, they do not make that transmission anymore (it is actually a 4spd with 2 lows available) and parts are very hard to get. Maybe switching to the Cummins ISB with a good Allison 2000 series 6 spd would be the way to go. Your old 6spd has 6th as direct, while the new Allison 2000 series has 5th (.75) and 6th (.65) as overdrives. So probably you would not have to change out your rear end ratio. Good Luck, TomC

Bob Gil · July 28, 2008, 04:41:34 PM

Quote from: TomC on July 28, 2008, 09:14:18 AM
While the 6spd Allison on your bus sound great, they do not make that transmission anymore (it is actually a 4spd with 2 lows available) and parts are very hard to get. Maybe switching to the Cummins ISB with a good Allison 2000 series 6 spd would be the way to go. Your old 6spd has 6th as direct, while the new Allison 2000 series has 5th (.75) and 6th (.65) as overdrives. So probably you would not have to change out your rear end ratio. Good Luck, TomC

Thanks Tom that was about what I was thinking. Since I already have the ISB I thinkit would be cheaper than rebuilding the 6-53 even.

I better wait and see how the 6-53 is going to run.

I went by the DD shop today to check on a alternator bracket and they wanted a serael number that i did not have so I ask where to look for it. The parts man went and got one of the mechanics and we talked for a little I ask more questions and he took me to the dumpster where they had some old engines for scrap and i found some of the brackest I needed to mount the kill slynoid and i was able to get them at a good deal. I guess with a shop like that one I might play with the 6-53 a little more than I would have other wise.

I was surprised to see how many parts the 8-71 had that I had on the 6-53.

TomC · July 28, 2008, 08:04:16 PM

You're discovering why the old 2 stroker Detroits were so well liked-is that they designed them extremely well. From the 53 to the 71 to the 92 series, there were many things in common. Like the rear gear train-many of the same alternators, power steering pumps, pulley drives, fuel pumps were interchangeable. Even on the 149 series were many items interchangeable. I don't think there has ever been a series of engines made that were more interchangeable than the 2 stroker Detroits. And to think that the 6-71 that was introduced in 1938 at 165hp @ 1800rpm, you could have bought in 1998 also when they ceased operation. Never has there been a single engine in production for 60 years in the same configuration, if you wanted. Course, Detroit also offered a marine version of the 6-71 at 485hp @ 2500rpm-just to give you an idea of the variation of horsepower offerings. Good Luck, TomC

Bob Gil · July 28, 2008, 11:57:39 PM

The 8-71 that I got the parts off of was one of the gov program replsce ment engines that was on a piece of equipment.

Has any body looked into seeing if they would do any thing for us in trying to update an engine in one of our buses?

I have a freind with a 1988 they gave him $110,000 to go towards purchasing a new truck. He will have to distroy the engine in the old one and show proff that is was done to the point is will not be reguildable.

Heck if they would give us $25,000 (or the cost of replacing the engine and upgrading it right) it might be worth it in the long run.