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Considering a CAT/ Allison swap

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77crewcab

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Well I am in posession of another Crewcab, this one a dually. I am looking at making a dedicated tow rig. I have a line on a late 90s Top Kick with a 3126 and an Allison 6 speed tranny. I am realy considering puting this combo into the crewcab I just got. It looks like I would have to notch the firewall some to make it fit and then start looking at making the intercooler etc fit up front. Anyone ever put any serious thought into a swap like this? I work for a CAT dealer and think this would make for a great combo in a one ton truck.
 
I think the 3116/3126 series engines are inferior, to other options availiable in the same time period or even slightly newer. with the heui injection...the headache with injector seats leaking coolant, then the pain in the ass changing injector seats. the nightmare timing the thing.

Do it if you want to do it, but I say its a boat anchor.
 
I work on these every day. They are cake to work on if you know what you are doing and have the proper tooling. The biggest problem is that they are usually put in trucks that are heavy enough to really need a larger engine, hence the percieved under performance. They are actually really good engines especially if they had been put into pickups like the Cummins 6BT was. Plus with access to the proper flash files more power is just a keystroke away.
 
77crewcab said:
I work on these every day. They are cake to work on if you know what you are doing and have the proper tooling. The biggest problem is that they are usually put in trucks that are heavy enough to really need a larger engine, hence the percieved under performance. They are actually really good engines especially if they had been put into pickups like the Cummins 6BT was. Plus with access to the proper flash files more power is just a keystroke away.
Click to expand...
I had considered this a little while ago. A CAT 3126 was semi-local for $400, but in pieces. I didn't know anything about hte engine so I passed. Being that your a CAT mechanic, I'd say go for it! It sounds like you have the know how and the means to make it a great set up.
 
Another CAT tech here, machines though, no trucks... 3126's and 3116's are all MUI that I have seen, they went to the c-7 and c-9 designations with the HEUI setups. The timing and load settings for a MUI setup aren't that bad, but you do have to have the tooling, and if your rack is worn getting it into spec can be a bit of a hassle, but nothing that is insurmountable. How would timing a HEUI setup be tedious? Its all electronic, provide the oil pressure to pump it up, and the ECM controls the rest. We do consider them "throw away" engines, but thats only in comparison to the liner'd blocks we have in the 4.75" (3300 series) and 5.4" (3400 series) bore engines. I've always wondered how a 3304 would do, it would be easy to fit, you've got liners for easy inframe overhaul, and pencil nozzles which are darned cheap. Not a whole lot of specialized tooling needed, but you'd have to keep the rpms way down, double overdrive or whatnot. I've dreamed about the 3126 swap myself, so I'd say go for it! (plus having the employee discount helps ease the bite of parts :D) And he's right, going from a vehicle of a 26k gvw to a 9k gvw truck makes a whole lot of difference in the longevity of an engine...

-Martin

EDIT: And you can always ream the coppers, not as good as new, but a good fix if you don't want to tear it down and have new seats installed...
 
I'm just saying from my experience in the Caterpillar dealer truck shop here in Calgary., where I did some of my apprenticeship. I saw more than a few 31 series engines in topkick trucks enter the yard on a hook. more than there should be statistically I think. again just my observation. the 3126E is HUEI injection though. I personally don't like the idea of useing engine oil to create injection pressure is all.
 
DEMON44 said:
I'm just saying from my experience in the Caterpillar dealer truck shop here in Calgary., where I did some of my apprenticeship. I saw more than a few 31 series engines in topkick trucks enter the yard on a hook. more than there should be statistically I think. again just my observation. the 3126E is HUEI injection though. I personally don't like the idea of useing engine oil to create injection pressure is all.
Click to expand...


Ah, there ya go, I've never actually seen a 3126E in any of our equipment. But we are about 5 years or so behind the truck scene as far as technology goes, and we don't get all of the new models and whatnot. All our new engines for machine, including our CARB repowers with C15s, C18s are all still HEUIs; as long as you are fastidious about changing your oil, we don't seem to have too many problems, sometimes the pumps go out, but changing them is an easy swap.

I got a chance to look at the newest ACERT technology last year (so I guess its not that new) but got to see the DPF's for the trucks as well as the high pressure commonrail c7s and c9s, very cool stuff, but damn its getting complicated. Can't even reuse fuel lines if you were to crack them loose on the new CAT common rails, supposedly too much risk of contamination.

We just installed our first DPF on a machine in the shop, a 623E, it was a PITA. If this is the future of diesel in California, I want the heck out...

-Martin
 
I had a line on a rolled Topkick and thought about doing the same thing. It's been done before and if you think about it, I don't see it being too much more difficult than swapping in a 6BT. I'm trying to find a picture of one and all I can come up with is one that was swapped into an F350.

F350 with Cat C7.JPG
 
My question would be the weight differnce between the 31 series and a 6bt?

IIRC a 6bt is around 1100lbs ready to run, if the cat is much more than that why bother?
 
1600 Lbs dry weight..............like I said before theres better options.








Specifications​
Configurations​
In-line 6 cylinder​
Cycle​
4-Stroke-Cycle-Diesel​
Bore x Stroke​
110 mm (4.33 in) x 127 mm (5.0 in)​
Displacement​
7.2 L (439 cu in)​
Governor​
Mechanical​
Aspiration​
Turbocharged - Aftercooled​
LxWxH (mm)​
1184 mm x 937 mm x 906 mm​
LxWxH (in)​
46.6 in x 36.9 in x 35.7 in​
Weight (Approx. dry)​
721 kg (1590 lb)​
 
ARAMP1 said:
I had a line on a rolled Topkick and thought about doing the same thing. It's been done before and if you think about it, I don't see it being too much more difficult than swapping in a 6BT. I'm trying to find a picture of one and all I can come up with is one that was swapped into an F350.
Click to expand...

Do you have the link to the site showing this truck? Thanks in advance.

Scott
 
I somewhat agree with Demon on this.

While I think the 3126 is not as heavy as 1600lbs, but it is a couple hundred pounds heavier than a 6BT (1200 is the number I come up with IIRC).

I have a 3116, it's a good motor, but it's somewhat complicated.

I don't really like hydraulically fired injectors, it just seems un-needed in my opinion. The International in the same class also use a very similar hydraulic powered fuel system and it seems like they are messing with oil pumps, oil pressure, picky types of oil, to really make the Fords make some power the with T444E. Just seems like an uneeded high maintenance system when compared to a common rail or even high pressure pump fuel system.

While CATs are really cool, a 6BT is a simpler, better engine IMHO.
 
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