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#846 - Cummins Swap
Author: andy1canada (Show all albums)

Howdy Folks!

Going to give this another try as my first attempt didn't go so well on the 'Diner-conversion' thread (Will update/edit that soon).

Started my Cummins swap by pulling off the bumper; only took better part of an hour. That sucker is HEAVY! Better part of a 100 lbs I bet. Will be looking to knock substantial weight off that baby while still retaining a 5000 lb towing standard.

This will take a while as it will unfold as time and resources permit, so please be patient.

More pics and hopefully some videos (FMC-TV) to follow.

Show Newest Photos First | Show Oldest Photos First210 Photos - Page : [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18]

I wanted to briefly revisit the brake drum yoke adapter that Billy and Lou came up with to simplify connecting the output shaft of the 47RH and enable the use of the short 8" OEM FMC driveshaft. You can find these quite readily available with a little searching as they (the transmission mounted park-brake) were used extensively on the old 727's in 70's era motorhomes and some med duty trucks IIRC. You'll know you've found the right one if it has 23-splines. Bill also advised that you can shave off another 1/2" or so by machining off the smooth inside end of the unit that has no splines. With a 12 valve swap, every little bit of driveline length you can save is crucial; however, I decided to leave it on this one as I feel it'll be slightly stronger left intact. I'll eat the 1/2".

Where you end up if you don't machine it off.

The aforementioned coveted Chrysler 727 transmission mounted park-brake drum with 23-splines, before the drum is machined off.

OEM FMC engine mount cross member - unmolested.

Extraneous stuff hacked off, ready to be surgically altered to hold a Cummins. There's pro's & con's to choosing to go with the OEM engine mount. One 'pro' is that you can leave the chassis support for the port-side mount in place and use it as is. One potential 'con' is that I'm not an engineer so there's considerable uncertainty (risk) that goes with this route. So I'm thinking 'over-build' to mitigate the extra torque and 400-lbs that the 12-valve brings to the party. Preliminary measurement dictated that the center section of the main beam needed to be lowered about 7" to allow clearance for the oil pan. What follows is how I addressed that.

First mod done. Measurements taken with the engine/trans sitting in place with the mount sitting in position (plumb under bolt holes in chassis). As it turned out our focus on installing the engine/trans as close to 'level' as possible, while ensuring sufficient ground-clearance, caused two issues: the 7" estimate to allow oil pan clearance was inadequate and the power steering pump is contacting the top corner of the end of the 4" beam. I will post a drawing of the finished mount when the corrections are made.

IMPORTANT: Forgot to mention how I managed to do this while maintaining the OEM length/position of the assembly. BEFORE you cut/weld anything (and the cutlines around the beam are marked) do the two bottom side(in pic) cuts first before you weld on the lower (arch) center section. Remember to also subtract the thickness of the end cap material you chose, if you cap them. These two undercuts will make cutting out that center section a breeze after the new arch is welded on, ensuring that OEM dimensions of the unit are maintained.

On the plumb cuts (top down)of the OEM beam I decided on a 5-deg. angle to match the same angle of upright lines of the arch beneath. Not so 'blocky' looking I figure.

Engine mounts (coach side)5/16" plate ready to weld. As I've discovered these mounts need to be revised to hold the engine an inch or so higher, I'm showing these now to stay in the order of how I arrived at where I ended up. Does that make any sense? I'll include dimensions in the final drawing when I get to it.

Next: after the engine mounts were welded and attached to the engine - with the engine/trans blocked in final position - and the engine mount cross-member temporarily bolted in place, I tack-welded both 2"x3"x 1/4" box steel horizontal mount support bars in place (yep, when you design your own shit - you get to name it!)
Show Newest Photos First | Show Oldest Photos First210 Photos - Page : [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18]

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