Detroit Diesel 6v53t engine

[Matthewd1960]

Does anyone have any experience with the Detroit Diesel 6v53t engine? Is it reliable, does it have a history of issues? This is powering a 1970 Blue Bird school bus that was converted to an RV that I am thinking of acquiring. It is a 30' bus with a raised ceiling. It has an Allison automatic and was regeared for the 6v53t. Owner claims it gets 12-14 MPG. He has all the paperwork for the conversion done by the previous owner and has about 9k in reciepts from the conversion from gas to diesel. Also, he boxed out the rear frame members with 3/8's inch rectangular box welded to the C frame and extending from just behind the rear wheels to the back end of the bus to support the heavier weight of the diesel engine and cradle. Will this create an issue at inspection time as the bus has been altered from it's original design? Are there any other issues I need to be concerned with. Frame appears to be solid, but has some scale. All cross members are intact. I'm thinking of having it surveyed or at least inspected before I commit to it.

 

[ol trunt]

While I am a great fan of all the 2 stroke Detroit Diesels I'd have to offer some cautions:

DON'T ever over heat a DD--not even once!

Don't lug the motor.

Don't over rev the motor.

Do have a professional oil analysis of the oil done before you buy.

Do be ready to be disappointed in the advertised fuel economy--most get about 1/2 that.

Do have a qualified DD mechanic evaluate the engine and installation including a nice long test drive including city, hwy and hills before purchase.

Do look forward to falling in love with the sound of a DD 2 stroke!
Jack

 

[Iceni John]

The 6V53 is a little screamer - it revs higher than the later 71 and 92 series engines, and because it's a two-stroke it sounds like it's turning twice as fast as a four-stroke. Torque isn't high, so you'll need to keep its speed up, but like any Detroit they can be run on the governor all day, provided their cooling system can keep up with it. The US military is still using them more than half a century after they were introduced, and Crown used them in some of their rear-engine Embree buses. For a 30-foot bus you should be seeing 10 MPG or better: folk with 35-foot Crowns with 71-series Detroits, even converted ones, are seeing 10 MPG or slightly more, and when I helped bring a friend's 40-foot 10-speed 6-71T Crown tandem back from Northern California it also was getting 10 MPG over the 500 miles, including going over Tehachapi.

Is the engine a turbo? You called it a 6V53T. If so, they're better than the gutless non-turbo 6V53. What transmission does the bus have? In those days there was a six-speed Allison HT70, but they're getting very rare now. Was the cooling system replaced when the 6V53 was installed? All two-stroke Detroits need an effective cooling system in top condition, or they WILL overheat: you need to carefully check the bus's radiator etc., otherwise you'll be having constant overheating problems.

Good luck, John

 

[Matthewd1960]

John, it is a turbo. Is this a V6 engine? It certainly looks like it, but I don't know big diesel engines that well. Not sure what transmission it is other than that it is an Allison. I can get the details from the receipts next time I view it. It does have air brakes. Is the 1970 blue bird hard to get parts for, or are they still available? Thanks for all the great background info on this engine! I'm still negotiating a deal, no cash straight trade. So not in the bag yet, but I'll use this time to research this beast so as to make an informed decision.

 

[EastCoastCB]

John, it is a turbo. Is this a V6 engine? It certainly looks like it, but I don't know big diesel engines that well. Not sure what transmission it is other than that it is an Allison. I can get the details from the receipts next time I view it. It does have air brakes. Is the 1970 blue bird hard to get parts for, or are they still available? Thanks for all the great background info on this engine! I'm still negotiating a deal, no cash straight trade. So not in the bag yet, but I'll use this time to research this beast so as to make an informed decision.

The v in 6c53 means its a V.
I highly doubt anything is stock about that. You'll be fabbing a lot of stuff for a rig that old. You better be handy.
IMO this isn't a good first rig for a noob unless they're real good at working on old stuff..

 

[Johnny Mullet]

This old bus will needs lots of love, but will last a lifetime.

 

[EastCoastCB]

This old bus will needs lots of love, but will last a lifetime.

depending on the condition of everything and the quality of the swap that was done.

Or did Bluebird put those DD's in buses?

 

[mmoore6856]

you can smell them a mile in front of you on the highway

 

[Matthewd1960]

I have been restoring VW campers for 25 years and have a full shop. This doesn't look like brain surgery to me. The bus runs and drives with the drivetrain only having 15k on it since rebuild.

 

[Matthewd1960]

This was originally a gas powered bus. It has been converted to Diesel.

 

[EastCoastCB]

I have been restoring VW campers for 25 years and have a full shop. This doesn't look like brain surgery to me. The bus runs and drives with the drivetrain only having 15k on it since rebuild.

I used to restore vw 25 years ago lol.
Just throwing a warning out that a 2 stroke detroit swap on a 50 year old bus isn't for the timid.
Can't wait to see some pics!

 

[Ronnie-SKO]

I used to restore vw 25 years ago lol.
Just throwing a warning out that a 2 stroke detroit swap on a 50 year old bus isn't for the timid.
Can't wait to see some pics!

Oh come on just a weekend engine swap....everyone does this just for giggles....

If I remember right it should be governed around 2800rpms for a 53 series. I had a 3-53 with 4 valve heads in an old pickup and it was governed at 2800. I had straight stacks on it, and yes we wore ear plugs.

 

[cowlitzcoach]

A 6V-53T is not going to be a powerhouse. Figure about 210 HP as the non-turbo was about 180-190 HP. With bigger injectors you might squeeze out 250 HP but the cooling system would have to be massive if you pumped it up that much.



The -72 and -92 series engines redline at 2,150 RPM's. The -53 series redline at 2,750 RPM. With the different cut on the gears of the blower on the -53 series and the higher revs it is going to really scream when you hit a hill. When you are pulling a hill with a -53 the closer to 2,750 you can get it to scream the better the engine will like it. Pulling below 2,100 RPM's and it will start to smoke and not like going that slow at all. Which is why so many of the DD equipped buses left the factory with Fuller Road Ranger multi-range transmissions that gave you 10+ gears, some of them OD. With 300-500 RPM gear splits you could always keep the RPM's between 2,200 and 2,700. With only four or five gears it is really hard to keep the RPM's high enough without dropping a gear and a lot of speed.


If you get the bus, do NOT EVER put in multi-weight oil. It will tend to not lubricate the top ring and break it. The ONLY oil that should be used is DELO 100 40 wt in temperatures greater than 40* F or 30 wt below 40* F. Shell Delvac, Mobil Rotella, and Texaco Ursa make a compatible oil but those brands are harder to get. Texas Refinery Corporation Pro-Spec DD is sold with free oil analysis. https://www.texasrefinery.com/product-specs/pro-spec-dd-motor-oil.pdf

 

[MacC-SKO]

Back in the day when our delivery trucks had 8v-7s we had a saying shut the door on your hand and drive it like your pissed. But in all seriousness the main webs and crank will not stand up to the torsional vibrations low rpms will produce.

 

[Booyah45828]

I looked for one of these for awhile. I know they were made but I don't believe they were too common.

A lot of people hit the nail on the head. Don't overheat it, Don't lug it, Service it regularly, and then sit back and enjoy the noise.

Oh, and I'll buy you a beer if that bus gets 14 mpg. Figure it to be about 6. 2 cycle detroits were better at producing noise then fuel economy.

Oh, and pictures and videos are a must.

 

[BigPaul367]

The 6V53 is small, sounds like this bus was built for level ground only. 53s over heat and die, don't let it over heat, keep the oil full and the coolant full because they both govern the operating temperature. 53s are SCREAMERS, they are loud and you better keep what ever sound insulation the bus has and you'll probably double it to reduce the noise. Stay out of California, the CARB and the EPA love to force people to replace their 2strokes, right now, reregistering the vehicle as a RV staves off the eventual, but eventually they will not let you register a 2stroke! 2strokes are easy to work on but the parts are getting herder to acquire and the market is getting flooded with cheap import pieces that can be very problematic. I am old enough to have worked on all of them, my favorite is the 471TT with Jake Brakes. Had an old IH one ton into which I transplanted exactly that motor, loved that truck. A cross country trucker fell asleep at the wheel and T-Boned it. That heavy old beast saved my life. The Motor was toast after that, I felt it was jinxed after all that, so I kissed it goodbye! Now I am looking for something into which stick my rebuilt 8.3 Cummins. Thinking about building/fabricating/welding my own 90 degree adapter for the oil pan and looking for a Crown of Gilling mid engine.

 

[Kubla]

CARB rules for diesel's only apply to commercial vehicles

 

[Sehnsucht-SKO]

CARB rules for diesel's only apply to commercial vehicles

For now...

 

[1970BlueBird]

I bought the bus.

Hey I found this thread while digging around. I bought the bus, drove it back to NH and she ran great. Didn’t even change a fuel filter. Now I am tearing it apart and getting a little too OCD. I paid 5k and was planning to outfit and run it. Now I’m getting carried away which I didn’t want to do. Anyone around for moral support lol. Northern NH here.

 

[BigPaul367]

The red color is a tip-off that this engine was rebuilt at one point. ALL original engines where original Detroit Green. Normally when a dealer rebuilds these motors they are sticklers about painting them the correct color. I hope the motor has a Magnetic Drain Plug. They are very helpful when tracking the health of ANY motor! Oil Analysis helps a great deal when servicing Detroit Motors.