Four stroke engine to replace 6-71?

[colecruzer]

Hi Everyone,
I have a 79 MC-5C which has a 6v-71 engine connected to a HT740 transmission.  Is there a four stroke engine suitable to replace the equipment I have?
Thanks - Rich

[RJ]

Rich -

Series 50, the four-cylinder little brother to the S-60, has been used in repowers of the MC-12s by Greyhound, so it should fit your 5C.  Need to get out the tape measure, for both length and height.  Width should be OK, as it's an inline.

Best would be to buy a complete transit bus with the S-50 and B500 transmission combination at an auction, then swap the entire powertrain.  That way you'd get all the necessary wiring for the computer controls (DDEC & ATEC).  Bonus would be the bigger transit brakes, Sheppard steering and sharper front axle cut for better maneouvering.

Another possibility might be the Cummins M-11 or ISL, but again, you'd need the tape measure, as these inline sixes may be too long  (that's why you couldn't get an 8V71 / HT-740 combo in the 5s, btw.)

For hot-rodding, a mechanical 6V92TA pumped up to 350 hp will be the easiest fit (block's the same length as the 6V71), as long as you provide adequate cooling for this set-up.  Then you could blow the doors off the 500 HP Prevosts climbing Rocky Top!   

Whatever you do, be sure to include an extra drop box for the rear axle.  They're becoming harder to find, so a spare is a worthwhile investment.

FWIW & HTH. . .

[TomC]

As nice as it sounds to switch out a 4 stroke in your 5, length is a big problem.  The choices are-as mentioned the Series 50.  Length and width would be fine, but it is a very tall engine.  You'd have to cut into your floor to make it fit.  Other 4 stroke 6 cylinders are just too long unless you create a hump on your back door (that would look real attractive) to make it fit.  Power wise, any of the pickup truck Diesels would work, but would still be in the 6-700lb/ft torque, so your performance wouldn't really go up.

The easiest is to switch your 6V-71 for a 6V-92TA (or even a non turbo-but are rare).  Both are exactly the same on the outside with the exception of having to add the turbo.  Then you'd have a real runner.

Please consider this- I turboed and aftercooled my 8V-71 increasing it from 300hp and 800lb/ft torque to 375hp and 1125lb/ft torque.  I had to replace just about every thing in the engine compartment or upgrade it.  Here's what was done.  The engine was fresh, so we used the basic engine adding a by-pass blower, turbo, and fuel modulator (to keep from smoking on initial acceleration before the turbo can kick in).  Had an air to air intercooler custom made.  Had the radiator increased from a 5 row straight fin to modern 6 row serpentine fin core.  New enlarged air cleaner and muffler.  Added an aux trans cooler. And had the transmission overhauled (needed it-was just slipping into 3rd).  Then added additional vents to the rear engine compartment door, side door by the aux trans cooler and to the intake stack to accommodate the larger air flow.  And I added a misting system to the radiator.  All in all about $17,000 worth, but it does drive nice now.  Good Luck, TomC

[RJ]

You'd have to cut into your floor to make it fit. 

Actually, Tom, he wouldn't have to cut into the floor on an MCI when installing an S-50.  What does have to be modified is the compartment above the engine where the radiator blowers are located.

If he could find a wrecked MC-12 that's been repowered, he'd be able to get the 330-350hp version of the S-50.  Maybe Sam Caylor at Caylor Supply has one in his boneyard?

FWIW & HTH. . .

[tekebird]

I would not want to Shoehorn a 4 stoke into a 5...there is hardly any room with the 8v71 in there

[akmc5]

Ha!!! If god didn't want us doin' engine swaps, he wouldn't have invented welders and sawzalls.   I'm lookin' at doing the same thing in the same bus.  Go for it, man.

[RJ]

I would not want to Shoehorn a 4 stoke into a 5...there is hardly any room with the 8v71 in there.

Doug -

That's why I suggested a Series 50 - they're about the same length as an 8V71, just a little taller.

[Brian Diehl]

Depending upon the size of your pocket book another excellent option is the Cummins ISL.  The ISL is very close to the same length as the S50, not nearly as tall and IIRC about 800lbs lighter.  It is available in configurations up to 400 hp.  A very dependable and versatile motor that would be perfect for the back of the MC5.

[James77MCI8]

Will a series 50 or M-11 slip into an MCI-8 easily?

[luvrbus]

Rich,the problem you will have is the dropbox on your bus it limits the type of transmission, if the S50 and the Cummins ISL are the same length as the 8v71 I don,t know what kind of transmission you could use

[Tom Y]

Rich, I do not think the S50 will fit.  It is longer than most think, unless you go to a shorter trans. That may not help because of the dropbox, The trans gets close on the drivers side in the bulkhead. Most to not know how short a 5 is in the rear. I added 15 inches to the rear of mine, I think you would need 7-8 inches for a 50 with a 740.  Tom Y

[Stan]

quote "Most to not know how short a 5 is in the rear. " unquote

You are right, but there are lots of suggestions from people who don't know.

[TomC]

Since I work with Freightliner, here are a few of the engines that are short enough to fit in our medium sized truck, along with some from other manufacturers.  Detroit Diesel Series 50-up to 350hp and 1100lb/ft torque (we put the Series 50 in the FL106 for awhile, but was an expensive option that didn't sell well-not to many people wanted a million mile engine in a medium sized truck-although expeditors loved them); Cummins ISL-up to 400hp and 1200lb/ft torque (this would be my choice); Caterpillar C9- up to 435hp and 1350lb/ft torque (very expensive engine); International DTA530-up to 350hp and 1150lb/ft torque.  These engines will be the same or a bit shorter than the 6V-71, and about 3-500lb lighter.  The only engine shorter than the 6V-71 is the 6V-53, which even in turbo form put out 300hp and 650lb/ft torque, but is a very noisy engine. 

Engines that would be to long- Detroit Diesel Series 60; Cummins M11/ISM; Cummins NTC/N14, Cummins ISX; Caterpillar C10/11/12/13; Caterpillar 3406/C15; any Mack or Volvo engine (Volvo is now making the engines for Mack-Mack engines no longer exist).  Good Luck, TomC

[Stan]

Tom: Would any of these engines go into a MC-5 without changing the cooling system to a side radiator because of height? That would introduce another set of problems with the engine sitting at an angle to the chassis.

[TomC]

Engines that are low enough would be the Cummins 8.3/ISL (my choice), Caterpillar C7, C9; International DT466/530 (another good choice); Mercedes-Benz 900 up to 330hp and 1000lb/ft torque (another good choice if you could find a recent junk yard Freightliner or Sterling).  You'd probably have to take out one of the radiators and install an air to air intercooler in its' place, since all modern 4 stroke engines use the air to air intercooler now (including pickups).  Good Luck, TomC