1991 3406b help 425hp

Discussion in 'Kenworth Forum' started by united972, Jun 17, 2021.

  1. united972

    united972 Light Load Member

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    Anyone ran one of these motors I have always heard great things about them but I’m picking up a 1991 Pete with a 3406b engine 3.55 rears 15 speed tranny 1.3 mil on the clock but truck looks to be kept in prestige condition.

    Can you tell more about this engine and what type of fuel mileage to expect?

    what would u guys pay for this estimated based on what u see pics attached
     

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  3. MLC Adventures

    MLC Adventures Light Load Member

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    EFI is a great thing in trucks. These old mechanical engines averaged 4.5-5 MPG. Wouldn't be thrilled with the 15. I'd expect to pay 23-24k depending, or I'd assume that's what it would bring at auction.

    Super solid engines though, with few issues. Injection pump problems will be a major problem when they arise. Few old mechanics are around that know how to build and time these pumps.
     
    Rideandrepair Thanks this.
  4. Rideandrepair

    Rideandrepair Road Train Member

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    Yep around 5, consistently though. Depends a lot on how heavy a foot you have. Much more so than an electronic engine. Those engines are great. # 1 King of the hill, #1 Drivers choice for quite a while. One thing to watch for is harmonic balancer. Sometimes they last over a million, sometimes only 500-750k. You’ll know if it’s bad. Very visible wobble at an idle. Can’t miss it. Good mechanic can work the fuel pump, changing springs, and really make them run excellent. If Pump starts leaking, time for a rebuild. Can be expensive. Lots of power, especially Torque. . Easily out pull a Stock 500 Detroit. The feel of the torque, when mashing the accelerator is really noticeable. Very fun to drive. I agree, Trucks worth at least $20-$25k. Not sure about parts availability. I’ve heard some nightmares about quality of not only aftermarket, but Genuine Cat Parts. I’m sure there’s plenty good stuff available. Just need to ask those who know. Water pumps would seep, from the weep hole. Supposedly upgraded around 1996. They stuck a piece of styrofoam in the weep hole, Lol. Absorbing the occasional minor seepage. Making it less or unnoticeable. I think rods and mains were suggested at 250k as a maintenance item by Cat. Probably good for a lot more than that though. Again something to ask those who know. Looks like an old Allied Van Lines Truck, with that sleeper. Kind of rare. What else? It will smoke and choke in cold weather. You probably already know that. Sounds like it’s bit the dust, till it warms up a bit. Then idles smooth. Quiet too. It’s the kind of engine you can’t help but like. Rotella changed out at every 10-12k miles, Cheap insurance. Some wouldn’t run right with other brand fuel filters. Avoid using the pump primer on fuel filter. It’s plastic and will wear out, or crack easily sometimes when used a lot. Just pre fill filters, if it runs out of fuel, use ether. Not worth taking a chance, breaking the primer pump. Truck looks nice, should ride and run just as good as any newer ones. Early-mid 90s, a mechanical was very desirable. No one wanted the new electronic engines. Much like the emissions engines fiasco. The E model proved to be a great engine, at 435 hp. I had a 92 C model with peec electronics. It was a 2-3 yr hybrid, or bridge motor. Had a mechanical pump, with a fuel cooled ecm mounted on it. Drive by wire and electronic cruise was the only benefit.It wouldn’t pull anywhere near the B and C mechanicals. Only difference between the 2 are C models had larger rod or main bearings. Not sure which,or both? Suggested changed at 500k, instead of 250k for the B model. I had them changed when I bought it at 500k, ran it to 1 mil. traded it off. Barely had any blow by at 1 mil. 5.2 mpg loaded or empty. Sometimes up to 6, if I drove it real easy, and treated the fuel.
     
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  5. united972

    united972 Light Load Member

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    Do you know of any mechanic that’s still around?


    QUOTE="MLC Adventures, post: 11417887, member: 317618"]EFI is a great thing in trucks. These old mechanical engines averaged 4.5-5 MPG. Wouldn't be thrilled with the 15. I'd expect to pay 23-24k depending, or I'd assume that's what it would bring at auction.

    Super solid engines though, with few issues. Injection pump problems will be a major problem when they arise. Few old mechanics are around that know how to build and time these pumps.[/QUOTE]
     
  6. Rideandrepair

    Rideandrepair Road Train Member

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    How about the Seller? Who’s he had work on it? Any history? The only thing somewhat obsolete is the fuel pump. Has to be plenty of Mechanics with knowledge of it. So much Old construction equipment out there with Cats. I had mine rebuilt at the Local Cat of Michigan Franchise. Cost $2300 in 1998. Pete and KW Dealerships usually had better, more knowledgeable Mechanics, specializing in Truck engines. The Cat Dealer by Me, mainly works on Construction Equipment. They were awful to deal with. Like ECMs now, there was always talk of that one CAT guy in Ohio, or Pa. etc. that could tweak the pumps just right. Only an issue if you want to turn up the HP.. Anything else can be done by anyone. Maybe post another thread, for a good Cat mechanic in your area. There’s some oldtimers on here, that are very knowledgeable. Good Luck if you buy it. Nice Truck. Looks like a solid moneymaker. The extra cost for parts, vs. a Detroit or Cummins from 1991 seems negligible today. Compared to the high costs of the emissions and new Turbo systems. That’s a nice simple engine. Good Luck
     
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  7. exhausted379

    exhausted379 Road Train Member

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    Try to catch Woreout. He can answer any question you have. He's busy with hay right now so he may be a little hard to catch.
     
  8. Stray_Dog

    Stray_Dog Light Load Member

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    Just so we're not putting misinformation out there so people that's unfamiliar with these engines don't start mixing parts and making mistakes and have a catastrophic engine disasters -theres actually quite a bit of differences between a B and a C.

    Also, a properly tuned Bor C shouldn't cough smoke and choke when started. The timing advance helps take care of that.

    That truck is worth somewhere around the 15k neighborhood in price without seeing it in person.
     
    Roger McG Thanks this.
  9. roundhouse

    roundhouse Heavy Load Member

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    I liked the mechanical 3406 that I had .

    inloike the mechanical Diesel engines Period.
    I had several mechanical injected 400 big cam Cummins Too

    Yes they use more fuel, but that’s balanced out by not being broke down on the side of the road because some stupid sensor went on the Fritz and left you stranded .
     
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  10. united972

    united972 Light Load Member

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    there asking 25k


     
  11. wore out

    wore out Numbered Classic

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    Trucks are high right now. Just an opinion but I think 25 is a stretch for that truck even as clean as it is. I sure liked my 15 no doubt.

    the thing about a B or C is it takes a guy that really knows them with the right tools to make them right. It’s hard to find a man that can make them right, without that guy there sorta useless.


    I wouldn’t consider 25k for my 91......that doesn’t mean it’s worth 25 to the general consensus.
     
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