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Discussion Starter #1 (Edited)
A few years ago Royal Rose here in Utah put a Cummins 6 AT motor in his FJ55 Land Cruiser. I followed the conversion close and took some pics. Royal mated it to a SM465 4 speed. He really needed a 5th gear.

Royal actually dropped in a Mitsubishi 6 Cyl first which ended up being anemic due to a bad head .
Royal replaced the Mistu with a Cummins 6AT3.4 and here is a few pics. Royal is a great resource if anyone is contemplating this conversion. Parts are getting a little spendy and harder to find IIRC and for power you might as well stay with a 4BT series IMO. Onan sells parts I believe.

here is a the source I found for Royals Motor.. he paid under $1k for it iirc



The First Pic was The Mistubishi 6DR motor
 

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Man, now I'm contemplating my choice of a 4bt.... Does anyone have more knowledge of this motor?
 

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Hi Sailed,
I just bought a 6AT converted f250. So... I will be learning as much as I can about these in the next little while. I am hoping to get great fuel economy, but am using a t18 4sp non-OD until I can swap something else in, so it won't be great. matt
 

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6AT in a 86 cj-7

Hey guys I'm new to the site but did a 6at conversion 6 years ago in my Cj-7. I'll post some pics when I get a chance, I had no idea these were popular! Gotta luv the web!! Getting 30 miles to the gallon with 40" boggers, 4.10 gears, with sm 465. Dana 60's frt and rear with hummer wheels. Will be repainting soon, but need to retime the pump, used to have the tool, does anybody have a source for it. I bought it from cummins years ago but can't find it. Also runs great on bio-diesel. Bought an xtreme bio diesel kit 2 years ago, run bio about 50% of the time. See ya Marty
 

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hi Marty. Yeah, great mpg #'s. Actually, these engines are not that common or popular, but they are out there. If your 6at has the bosch VE pump, it should use similar tools and procedure to the 4 or 6bt VE's. This might be one of the only parts similar between the a series and the b series. My a series shop manual shows the VE timing tool as pn 3377259. See if crewcab59 can get it for you. If it has the stanadyne pump, no idea??? If you need some more info from the cummins shop manual let me know. Matt
 

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timing on the 6AT

Yea there starting to be a little harder to get parts for. I found the tool, in my shop buried amongst gaskets and misc. parts. What I can't read on the data plate is the timing setting. I have the manual also but it does not give exact setting for timing, just plunger height to start with at 15 degrees, 2.2mm. The automotive set up Has different timing than the genset obviously. Cummins used a timing setting and stamped it on the data plate based on which injectors, and pump used. They also used a stanadyne on this engine.
 

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Asheville huh!!

Hey my whole family is from N.C. Weaverville, Arden, and my brother still lives in Yadkinville...near Mocksville. Small world!
 

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timing on the 6AT

I just bought that timing tool from Cummins for $270 :eek:
My 6at3.4 is missing the data plate on the valve cover. Does anybody know what the timing number is for a 6at with a 120 hp ve pump? I'm having issues with the lack of fuel pressure leaving the pump and not all of the lines out are spraying fuel and I want to make sure it's timed right before I pull it off and have it serviced...

Thanks in advance,

Kevin
1980 Scout II Cummins 6AT3.4
 

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we have got some of those in generators at work.
and i just rebuit one..

the story i got when i whent looking for parts.
is that cummins 6A /6At was designed and built by Onan
before cummins bought them out.. and cummins just rolled them into the product line..
judging by the newer Onan generators..The 6A/L634 series has been completly replaced by the B series.



mine are pretty old (pre 1983) and do not have any cummins id or casting #'s at all but are listed as Onan L634's
(ie L- 6 cylinder 3.4's)

i dont think they are built as stout as a 4BT.

the ones at work have stanadyne pumps on them
and there are no accessory openings or covers in the gear case to mount any thing other than the injection pump.

they use stamped steel rockers on fulcrum studs not shaft rockers like the B series.. and have a spray bar that runs under the valve cover.

also uses an SAE #4 housing- cast iron
 

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I realize this thread is getting a little old, but... My 6AT as indicated on valve cover: Static timing 0.98mm plunger lift at TDC.

I'm having issues with timing as well. not sure about the correct procedure to use. It seems like there should be alot more plunger displacement at TDC, unless the plunger is on its way back to closing. I'm assuming you would zero a dial indicator when the plunger is a the bottom of travel.
 

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I was able successfully time my 6at using the above info at .98mm/.039 plunger lift at TDC. Engine now runs great.
 

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Also DSE do you have the serial no to the 6at as I cant read mine on the plate and I cant order my head gasket from my cummins dealer without it. Any help would be great!
 

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just stuffed an A-series (4-cylinder 2.3L turbo) in my jeep wrangler

I will look up what the headgasket is for a 6at later tonight
 
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