Brian's engine swap thread

[edroelle]

When cleaning up surfaces, do NOT use Scotch Brite disks or pads.   They have carbide in them and if they are not cleaned up completely, you may have a bad day.   Some car engines failed shortly have rebuilds because of this problem.

BTW, I exchanged an 8V71 with a truck 8V71T with similar hurdles as you.   You are on the right track though.

Ed Roelle
Flint, MI

[TomC]

To me, that low profile rear mounting of the turbo looks to be just the setup for the 5.  But-you're already talking of a side mounted turbo-too bad you couldn't keep the turbo where it is-even if you had to extend a bit to clear the accessaries.  Good Luck, TomC

[christopher]

Brian, You can raise the blower deck as there is plenty of room to go up. My 5C had a 671 changed to a 692t. The deck was raised to accomodate the engine. Let me know if you want a pic
Thanks
Chris
mci5c

[bevans6]

I'm trying to be as non-invasive as possible with the swap.  A local friend Carl has installed an 8V71T in his 5C with a front/top mounted turbo, and he did that by doing away with the fan gearbox and using a hydraulic fan motor.  I could probably do that.  The problem with the rear mounted turbo is that it is low enough but it completely obscures all of the accessory mounting locations, so I would have to find other ways to drive the power steering pump, the air compressor and the alternator.  Of the options, I really think that putting the turbo on the side is going to be about the easiest.  There is lots of room, I get a straight shot down to the stock muffler location for the exhaust, the air intake will be easy - I may in fact retain the existing blower cover and do a little S-bend for the air intake hose.

I build custom racing headers so I don't see a problem with the manifold fabrication.  I'll just buy in some bends and use the existing flanges to the cast iron manifolds.  I will probably make the air plumbing out of aluminium bends and join with hose sections.  I think the main disadvantage of the side mounting is that the turbo lag will be greater so the engine will be less responsive than a mid-mount with shorter  and more equal exhaust plumbing, and it will be hard to get into the valve cover to check that without taking the turbo plumbing and maybe even the turbo off.   So - I'm still thinking about it.  Today I've been thinking about a low front mounted turbo and modify the doors on the bus for clearance.

Chris, I really would appreciate seeing pictures of your installation, you could post them here or email them to me.

Thanks for all the input, I really appreciate it.

Brian

[Prevost45]

Brian
Put the turbo where it fits best, Use good mandrel bent heavy gauge bends, No leaks !
Good oil return to the pan/block . That DD 2 stroke moves a lot of air , will not know a
foot or two added to exhaust or intake piping

[luvrbus]

On a side mounted turbo you can get faster response, spool up and boost pressure if you change the big 71 series manifolds and pipes over to the smaller 92 series manifolds and pipes fwiw  



good luck

[bevans6]

So, an update on this project, finally...  I am here to testify that one person who's never done it before, working alone with hand tools can indeed pull the engine/tranny on an MC-5C, but it is not what I would call relaxing entertainment...  That said, it's done...

The hardest bits were the plumbing - there is more of it that I would have ever imagined and it goes everywhere seemingly randomly, so tomorrow I am going to draw it all out.  Ain't no way I would figure that out going back in five months from now.  And the driveshaft.  Yes, it's only like 8 bolts, but they are awkward to get to if you need to put any leverage on them, the parking brakes are set on the bus and I had no way to put air in to release them so I couldn't rotate the drive-shaft to get at the nuts you can't reach,  and one was frozen in so hard I had to heat the flanges and drift it out with a hammer.  All in all, including cursing, getting the rear wheels off so I could reach the flange, finding my portable torch set, finding the lighter, going inside to warm up (below freezing and snow flurries) - that part of the job took over 4 hours all by itself.

Other things of note - the dolly was made to the dimensions in the MC-9 manual and it's about an inch and a half too long for the MC-5 to do it right and easy.  I had the bus jacked up at the proper body jacking points and the rear legs of the dolly hit the jack just a bit before I had picked up the rear of the engine block with the rear uprights.  I actually had it almost at the balance point and had to tie the front of the block down to the dolly or it rocked a bit.  Now it's out, getting it in the shop over a 2" step in the pavement was just some routine rigging.  But I can tell you for free that your 8V71 with your Spicer gearbox does not roll with ease even on your brand new 1000 lb rubber tired casters.  Making it roll somewhere that you want it to go is  a job for about four 240 lb men, not one...

[RickB]

Hey Brian,

If you decide to stick with the belt driven stock cooling fan system make sure you put the smaller diameter pulley on the top gearbox. The one you have could have the deeper grooves with the larger overall diameter it is hard to tell from the pics.

Sobering post for anyone who wants to do a military or truck motor repower. It is alot of work and alot of modification . You better know or be a really good welder and you better have extensive mechanical skills if you're gonna try it. I learned that last year when I bought the truck motor last year that just some of the changes were: motor mounts, water pumps, pulleys, oil coolers, bellhousings, flywheels, and just the backplate was $700 and took experienced DD mechanics a day to remove and a day to reinstall.

It is obvious that Brian's experience and shop are going to help him do this right but it is a sobering reminder this kind of repower is not for the faint of heart. Heck, pulling a motor that heavy is not for the faint of heart. We had the front end of a huge dump truck a foot and a half off the ground to separate the motor from the tranny. scary stuff.

Good luck Brian and keep us informed.

Rick

[luvrbus]

Yep Rick you got to love what MCI did on the back of the Detroits I do not like that change over lol

good luck

[Iver]

I can appreciate the amount of work having pulled my engine by myself.  The dolly I built looks somewhat different and I copied the plans in the manual as well.
However, I had to drive the bus up on ramps to get it high enough to get the dolly underneath.
Having a pit and a tractor.......priceless.
Good job..
Iver

[TomC]

Looks to me that if you eliminated that big 50DN alternator from the rear of the engine (a big pain to change if it goes out-it weighs 100lbs!) you could use that rear mounted turbo from your replacment engine.  Good Luck, TomC

[bevans6]

The turbo on the rear mount is about exactly where the air compressor goes, unfortunately.  I would have to lose the DN50, and find a new home for the compressor and the power steering pump.  And cut a hole in the floor, the turbo would hit but only by a couple of inches.  The only way I can think of that doesn't include cutting bodywork is the side mount.  Even then the DN50 belt drive is going to be in the way.  There just isn't a lot of room above the back of the engine in the MC-5C, I had to take the governor off the air compressor or it would have hit when I lifted the engine to slide it out.  There is literally a half inch of clearance over the compressor to the floor of the bus.

Brian