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Consider the Tiny-Tach, the transducer clamps on an injector line.


You need to know the diameter of your injector line - There are 1/4 inch and several Metric dianeters.

My Tiny-Tach is on it's second vehicle and has over 70,000 miles on it.

Thanks guys. Here are some photos (I hope).
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Consider the Tiny-Tach, the transducer clamps on an injector line.


You need to know the diameter of your injector line - There are 1/4 inch and several Metric dianeters.

My Tiny-Tach is on it's second vehicle and has over 70,000 miles on it.

The pics may be confusing.... I did the entire swap first on an untitled junker frame from a 47 tonner. Se easy with no sheet metal (I'm 67 years old).... I even drove it around the property with an old seat mounted and no brakes. 'cummins 6at death trap' on youtube. You can hear me crashing through the chicken pen and killing the engine with my dash mounted household light switch kill switch. Just before the big mountain slope........
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No, I used the ford pedal mounted under the floor. It originally had a short rod and clevis to the clutch throw out arm on the driver's side ... Well the 6at with gm bellhousing has the clutch arm on the pass side. , so now we're a long ways away. I made a long, almost 2 feet pushrod from some lightweight tubing I found at the dump. Welded a fine thread nut at each end. Mated that to a wilwood clutch master cylinder. 7/8" . Crossed over to the pass side with a braided stainless line from amazon and connected to a 'pull type' slave cylinder also from wilwood. Now this pull cylinder is a cool thing for swaps. You really need to adhere to the instructions about angles of pull, apex of curve etc or I have read it can put side thrust on piston, causing premature wear. The reason I used this unusual combo is because it still looks bone stock on the interior and I didn't wan't to cut up my firewall for pendulum mounted pedals.It took a few trials, but for my project I ended up with 7/8 on the master and the slave.
 

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From what I have researched, they were installed in a bunch of UPS trucks in the late 80s. Most of them replaced a chev 292 inline six. Also 'here-say', but after about 5 years of driving and working in a tin box with a clattering diesel at their right knee, the drivers revolted and the 6at's were removed and a gm v6 was installed in it's place. The 6ats were sold off in lots and they made their way to the swappers. I have spent years on the old ford sites and one of the members worked at cummins and sent a link to a 36 page document printed in the SAE journals about Onan's development of the L634 engine series. The series was available in 3,4.and 6 cyl varients and generator, marine and auto use. In trucks, the market was 8,500-14,000 GVW class. (Keep in mind this is a 210 cu in engine) . Cummins bought Onan and rebadged this engine as the 6at. The 3600 rpm thing is good when replacing a gasser and keeping stock gearing. I really love this swap keeping my 4.86 rear for the 40-50 mph local speeds.
 

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I'm idling at 825 rpm. Can't seem to get it lower, but sounds fine. Running down the road at 3000 she's a screamer. Can't imagine being around one on a genset running 3600 all day (or all year). Just a sheetmetal floor and firewall and a short straight pipe at this time though. Loving the tach!
 

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I have a 6at in my 1970 Chevy k10 sm465 205 3.08 gears 31/10.50/15 tires I can do about 70mph at 2400rpm turned the fuel screw in about 3/4 of a turn on the injection pump takes a half inch wrench and a screw driver. It will turn your idle up to about 950rpm factory setting is 750rpm. It makes a world of difference it does woof a bit of smoke now I have auto meter pro comp ultra lite boost and pyro gauges. with where I have it turned up to it runs about 950-1050 deg under full load on the hiway. Definitely seen a big increase in hp and tq
 

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That looks like a great swap! And quite successful as well. I finally took mine off the island for a couple of days and hit interstate 5. My speedometer is not accurate at all so I did the research with the plug in formula on the spicer site. I averaged around 2750 rpms which got me about 59 mph. I did a stint at 3100 which calcs to something like 64 mph. I don't have the figures in front of me. I have stock 4.86 rear, 34" tires (7.50x17) and 1-1 final drive in the tranny. At 2500 rps and up, she just takes off. Full boost and in the zone. In the sae papers, it mentions that during development these engines were rigorously tested and something like 38 engines were run for 3000 hours at 3600 rpm under full load with no mechanical failures. They were also tested and rated for occasional overspeeding to 5000 rpms without failure. Yikes! At 3600 rpms I should be doing about 75. Too fast for this truck in my opinion. My fuel mileage at these higher rpms was 16.8 mpg. I run around my island at about 1500-2200 and I'm sure the mileage is way better at those speeds. All in all I am extremely happy with this swap.
 

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Does anyone with the Onan L634T-A know where to source a rear main seal or know of an appropriate replacement? Cummins discontinued. All OEM resellers out of stock. Im sitting on the rack watching the $$ add up every day.
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