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Location: Corcoran MN 5340
(66.41.214.112) | I have inherited the fmc coach from my uncle. He did a diesel engine swap a number of years ago. I drove the coach different times be for the swap and it drove incredibly well. Since the swap you constantly are steering to keep it going down the road straight, "white knuckled".
the engine used was a 6.9 L ford/international with a C6 ford trans behind it. Think it came from a 1984 F250 pickup.
tried alignment, new 19.5 tires and wheels, adding a rubber bumper spring on the advice of Jim Black, an fmc engineer with fmc at the time they were built that owned Recreational Vehicle Services, This helped a lot but still not good.
Went to a heavier bumper spring but no change. Thinking I need to add a tag axle but don't want to if at all possible.
info I've found on engine weight is that the 6.9 weighs #860 and the original 440 #670
Any one had issues after doing a diesel swap?
Any help appreciated I'd sure like to use this | |
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Location: Cottage Grove, OR
(71.94.238.133) | Tom, Welcome to the Club website!
When the engineers designed the FMC, a certain weight balance was achieved that enabled good handling. When a different and heavier engine is installed that balance is disrupted. One effect is on the handling of the coach as the added weight in the rear is behind the balance point of the coach body. That reduces the weight on the front end and increases it on the rear of the coach. To get the handling back to nearer to the original level, that imbalance must be corrected.
To my knowledge, there are two ways to achieve this. One is add weight to the front of the coach by adding weights behind the front bumper until the original weight balance is re-established or by adding air bags to the rear of the coach placed behind the rear wheels. Both have worked for other diesel engine conversions. I prefer the adding of air bags. There are photos of how it has been done in the photo gallery section of this website. | |
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Location: Oceanside, CA
(70.183.106.155) | The C6 is probably the same weight as the 727 so that would be a wash; so, you're really only plus 200lbs in the rear, that alone shouldn't make that much difference in handling; but, getting rid of the original onan generator and going with a modern 3000-5500 watt unit can cut nearly all of that added engine weight. Additionally, if you have a rear mounted spare tire, moving it to the front bumper is a big help.
Air bags are really what you need to stiffen up the rear suspension and keep the sag and sway from starting, that will dramatically improve your tracking. | |
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Location: Corcoran MN 5340
(66.41.214.112) | Thank you Steve, I now have something to work with. Much appreciated | |
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Location: Corcoran MN 5340
(66.41.214.112) | Steve, not seeing any pictures in gallery? | |
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Location: Corcoran MN 5340
(66.41.214.112) | Steve, not seeing any pictures in gallery? | |
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Location: Oceanside, CA
(70.183.106.155) | tom gleason - 2019-05-17 7:52 AM
Steve, not seeing any pictures in gallery?
did you try either of the links I posted? | |
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Location: Cottage Grove, OR
(71.94.238.133) | The first link that Len posted is to the ones that Frank Borrmann installed. The second link is to the album for Len’s build. You will need to go through the album to find the photos of his airbag installation. They are there! Len put them in both the front and the back while Frank just put them in the back. | |
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Location: Corcoran MN 5340
(66.41.214.112) | Thanks guys, WOW what a nice job you did on your coach Len! I know you fabricated the lower arms you installed, did frank as well or is there a kit available? Do you remember what weight rating the air bags were? | |
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Location: Cottage Grove, OR
(71.94.238.133) | Frank also fabricated his. There is no kit. | |
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Location: Oceanside, CA
(172.10.134.245) | tom gleason - 2019-05-17 1:18 PM
Thanks guys, WOW what a nice job you did on your coach Len! I know you fabricated the lower arms you installed, did frank as well or is there a kit available? Do you remember what weight rating the air bags were?
Thanks for the kind words; I don't recall the weight rating but they are Air Lift Dominator 2600 bags, 8" diameter, 12" tall inflated height.
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Location: Scottsdale, Aridzona
(24.251.181.209) | Hello Tom,
I have a GASOLINE engine in my FMC, so of course everything I say is just like the buzzing of a fly near your ear. Long long ago . . . I did some work with some other really smart fellows on putting a Compounded Diesel Engine in the AGM 86B Cruise Missile engine, for DARPA (Defense Advanced Research Project Agency) . . . and a different Compounded Diesel Engine into a Helicopter for the US Army, . . . but that is certainly nothing like changing a FMC 2900R to a Diesel Engine with some "other" Transmission.
Made a quick search in the Coach DB (Tab in Header) and noted there were 17 FMC Bus Made with the 4V-53 Detroit two stroke, apparently none still in operation. There are 59 FMCs of A, J, M type (which included your FMC #244 with a FORD Diesel/C6) that are stated as having a changed Diesel Engine, but all Engine ID, Cummins, Detroit 8.2, GM Duramax, other, are not listed, nor is transmission make/type for each entry.
So, of the 59 "CUSTOM/MODIFIED" Diesel Powered FMCs listed in this website Data Base . . . TWO have owner fabricated AirBag rear suspension . . . Frank Borrmann's #645, and Len Baron's #1027.
The other 57 (which included yours) have Torsion Bar rear suspension as it came from the "factory", perhaps with added Timbren Rubber Springs, and maybe one, Jim Woestman #617, with "bigger torsion bars" in his Diesel powered FMC. Seems that 59-2=57 other Diesel Powered FMCs have suitable steering, as so far, those owners do not seem to be having any issue that they have brought up to this FMC Owners Website. I know of one particular Diesel Powered FMC that has had two different Owners in the last few years, and both Owner's seem(ed) perfectly satisfied with the steering of that FMC with the 8.2 Detroit and Allison (can't remember Type). The setup/location of that particular engine/trans is very typical and can't be that much different than your Ford Diesel/C6 (?) setup. #244 has Spec Load of 5,000 Lbs on the Front axle and 9,500 Lbs on the rear. Think at FMC #646 the GVWR went up about another 800-1000 Lbs.
Perhaps, you should weigh both ends of your #244 FMC to have a "starting point", and then examine the front steering completely . . . rag joint, steering box, steering box mounting, steering box adjustment, all rod ends, steering and idler bell cranks/bushings, front spring shackles/pins, front spring, shocks, A-Am bushings, and of course wheel bearings. Timbrens old and HARD ? Replace with #A103B-75. Wheels on tight ? Anything need repair/replacement or service ? I would do that before I added air bags aft of the rear axle. Both the FMC Air Bag modifications on #645 and #1027 are crafty work, and report as riding/steering great . . . but 57 other FMCers with Diesel Engines seem satisfied with the stock (maybe + Timbrens) suspension/steering. Many Stock 440/727 FMC owners have reported poor steering . . . that in general has been corrected with suitable maintenance/alignment.
Oh, two last thing(s) . . . Rule(s) of Thumb(s) . . .
1. Do NOT add any weight behind the rear axle of a FMC. (That includes BUMPER STICKERS !)
2. A FMC can not have enough CASTER !
Steer Straight ON ! Lou #120
FYI - http://timbren.wpengine.netdna-cdn.com/wp-content/uploads/2017/11/A...
Note load (page 2 Part # A103b-75) and deflection vs load curve (page 3),
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Location: Oceanside, CA
(172.10.134.245) | I agree with Lou's recommendation to get yours on a scale before you spend any time or money on "fixing" it. Lou's point about whether or not airbags are needed is also valid, if I didn't carry high tongue loads/tow fairly heavy with mine I could have probably lived without them...but...I believe if you talk with either Stephen or Rico (both with diesel rigs and no airbags) you'll hear that both want to get them installed. Honestly I think that most of these coaches with 40+ year old torsion bars could benefit greatly from air bags but it is a tough/expensive mod to do and in the end if your happy enough with the handling the "juice won't be worth the squeeze"..
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Location: Cottage Grove, OR
(71.94.238.133) | A little added information. Rico has added airbags to his coach. I have not as of yet, but would like to do so. My engine is a Duramax which is lighter than Fords, Cummins, or Detroit’s.
Lou has do a good job of analyzing the information in the database but much of that information is 15 years old or older. As to diesel powered coaches and their handling characteristics I don’t believe that just because it isn’t reported on this website it does mean that it doesn’t exist. I am in communication with two owners that have recently purchased coaches with diesels and both have handling issues they are/will be attempting to correct. Both of those have Detroit 8.2 engines. Anther coach was purchased with a Ford diesel and due to poor handling has been put in non-operational status by the owner and it sits in a storage lot.
Also I am aware of one coach in Canada that still has the original 4 cyl, two stroke diesel that it had when built by FMC. | |
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Location: Corcoran MN 5340
(66.41.214.112) | Well I got to work and checked the suspension over. I had been playing around with the steering gear adjustment early on and it was set too tight, so I corrected that. We had replaced the the bumper springs that I originally added with air bags in the same location, ahead of the rear tires. but the system developed a leak the needed to be corrected. I moved the spare tire to the front, seemed to make a noticeable difference and had it aligned again. We were able to get just under 5 degs +caster and it really drive much, much better. I think I'll still move the air bags behind the rear wheel like Frank and Len have done. but I think it's a road worthy unite again. Thanks again everyone for the info and advice couldn't have done it with out you. | |
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Location: Corcoran MN 5340
(66.41.214.112) | Well I got to work and checked the suspension over. I had been playing around with the steering gear adjustment early on and it was set too tight, so I corrected that. We had replaced the the bumper springs that I originally added with air bags in the same location, ahead of the rear tires. but the system developed a leak the needed to be corrected. I moved the spare tire to the front, seemed to make a noticeable difference and had it aligned again. We were able to get just under 5 degs +caster and it really drive much, much better. I think I'll still move the air bags behind the rear wheel like Frank and Len have done. but I think it's a road worthy unite again. Thanks again everyone for the info and advice couldn't have done it with out you. | |
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(76.253.13.76) | Hi all. Does anyone have a live part number for the rear hydrovac check valves. Item 56 be-2511066. Or a alternative. Thanks | |
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Location: Oceanside, CA
(172.10.134.245) | Payesko - 2019-06-24 2:43 PM
Hi all. Does anyone have a live part number for the rear hydrovac check valves. Item 56 be-2511066. Or a alternative. Thanks
I don't think this has anything to do with the topic of "diesel engine swap"; probably best to start a new thread in the mechanical section or add to an existing brake related thread to get some better feedback.
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(71.198.125.209) | My apologies. Thought I was on the thread directly below yours. | |
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Location: Corcoran MN 5340
(66.41.214.112) | Midland part # is RV10001K they should be pretty easy to find. Are you having trouble locating one? | |
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