Gillig Need Help 743 to 855 conversion. Any Ideas!

GilligSkip · May 28, 2013, 03:25:28 PM

I have one of the 68 Gillig MGM buses and lost the 743 Cummins. If possible I want to install an 855 big cam and think someone out there had info on converting a standard 855 big cam to a pancake. I can go with the small cam but I've talked to several serious Cummins types that say "if you can do the big cam, do it! It seems that the big cam is a much better engine than the small cam. The small cam is known for cracked blocks. Two large Cummins shops I visited will not warranty any small cam work for that reason. Someone on here, some time ago, mentioned that they were aware of the process to lay down an 855.
ANY IDEAS WOULD BE VERY APPRECIATED.
Gillig Skip

luvrbus · May 28, 2013, 04:20:09 PM

Why not buy a 855 from a Gillig they used the 855 pancake in the late 70 and 80's then you have the 855 used in the Crown/Ikarus surely those old engines are not that hard to find are they ? I have heard the parts to lay one on it's side are expensive

Uglydog56 · May 28, 2013, 05:39:14 PM

Skip, to lay down a big cam, you basically need a small cam pancake engine plus a new accessory plate from Cummins. I haven't done this, I've just done a lot of research. I have a small cam turned up to 350 hp. It outpulls just about anything and the pyro doesn't go above 900. I can give you my recipe or sell you the whole engine as my bus was recently destroyed by a drunk drver.

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wg4t50 · May 28, 2013, 06:04:01 PM

Would be great if you could get the Engine number & CPL # from the Big Cam pancake, that would give you all the part number info needed.
Be lucky
Dave M

HB of CJ · May 28, 2013, 06:20:18 PM

Later model Crown Supercoach schoolies, (1980-1992) are being placed out of service; put up for sale cheap; then if no buyers, (out of state only) the coaches are being crushed whole.

You need a Big Cam Pancake Mill out of a Crown. Too many parts, (so I was told) will not interchange between the 743 and 855. Also the Big Cam will hang down more.

Some fabrication required, like for engine mounts. Or....as I was only told, you can knotch and crib the frame and hang the Cummins Big Cam higher. HB of CJ (old coot) (VIN 37317)

TomC · May 29, 2013, 08:25:20 AM

I know Crowns do not have a frame in the back behind the rear axle. Do Gilligs? If the Gillig has a rear chassis, why not convert to a rear engine? Then you're engine selection will be vast.Being tied to using a Cummins big cam engine isn't all that great. Yes you can get 475hp out of them, but they are maintenance intensive. But-it is your bus. Good Luck, TomC

joel_newton · May 30, 2013, 09:10:13 AM

Tom, Great idea!

I have 6 1/2 feet of frame rails from the back of the rear duals to the rear of the bus. It's continuous rail with cross members. I had thought about adapting a rear engine. Plenty of room! Skip may have 4 1/2.

One aspect I'm not clear on is reversing the rear axles. Do you get a CW - CCW problem? Wouldn't realigning the axles be a challenge?

TomC · May 30, 2013, 09:20:25 AM

To make a mid engine to a rear engine, picture taking the entire assembly and rotating it around the axle. You could just rotate a 23,000lb axle to have the input shaft face backwards then have the spring pads welded on. Gillig did make rear engined buses-using the 3208 Cat and 555 Cummins engines (neither I'd suggest). A good Cummins ISM or Caterpillar C12 would be ideal because of their smaller size compared to the NTC big cam or ISX15, and the Caterpillar 3406/C15. You could simply find a wrecked truck with an autoshift transmission then install with the radiator in the back-just changing the radiator fan to a pusher. Good Luck, TomC

kwidd · May 30, 2013, 08:59:31 PM

I turned my 57 crown mid engine bus to a rear engine. It now has a cummins L10 and an allison 4 speed trans. I dropped the rear section of the frame. I found a rear end and air ride out of a beaver motor home. I use a hydraulic fan drive with radiator on the side. I wish it had an M11 engine but you can't have everything.

GilligSkip · June 03, 2013, 10:44:35 AM

Thanks for all the suggestions. Re making it a rear engine, I can't because we put our car in the Gillig through back doors.

Any other detail on making a big cam a pancake would be appreciated.

Rick, I'll call you when I get back from my next road trip and go over the details with you. I'm still in the big cam vs small cam mode but if I can get the big cam in there it would be the best option. I'll also try to get ahold of Patrick again to see if he replies as he has what I believe to be a small cam pancake out of a Crown - condition unknown. Not much time right now as it's hay season.
Thanks.
Skip