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help choosing convertor

Discussion in 'Transmission & Transfer Case' started by White85, Oct 10, 2019.

  1. White85

    White85 Full Access Member

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    hey guys im hoping someone more knowledgeable can help me with finding a convertor with a good stall for a project i have going. The frame is a 77 k10 shortbed with 49 willys body and a 14 bolt in the rear and a dana 44 in front from a 3/4 ton truck and they currently have 3.73 gears. the engine is a 350 with TH350 and np205. engine build is just above mild i suppose with forged crank, aluminum heads, roller rockers and air gap intake with roller cam specs as follows, advertised duration 296/300, lift .539/.548. about 10 to 1 compression. hope it to be close to 400hp at the crank. truck should weigh in around 4500-4800 lbs i hope. tires are maxiss trepadors 40x13.50r17 if someone can help or if they can but need more info i will get what i can. thanks in advance

    Since pictures tend to catch attention and help out here is one. thanks
    1189AC6E-E90A-441C-A68A-5E3C2E7857A9.jpeg
     
  2. bucket

    bucket Super Moderator Staff Member

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    What are the specs on the heads?

    I'd say about a 3k stall and a lot more gear.
     
  3. White85

    White85 Full Access Member

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    heads are blueprint h8002k. 195 cc intake 64cc combustion. i would like more gear but thats what i have for now. thanks
     
  4. TubeTruck

    TubeTruck Full Access Member

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    Yep, 3k stall and at least 4.56's. What are you looking to do with the truck? just a cool driver? wheeling? mud?
     
  5. QBuff02

    QBuff02 I like Big Blocks and I cannot lie

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    what are the cam specs at .050? and what is the advertised power band of the camshaft? Those two things play more variable into converter selection than just about anything else. Based off the advertised duration i'd venture to say it's in the neighborhood of 230ish degrees at .050. Which will put you into the area of a 2,500-3,000 rpm stall. which means You'll probably end up with a smaller than stock diameter converter right out of the gate. Lighter vehicles and smaller cube engines tend to need steeper converters as there is less resistance to acceleration. Also the torque range/curve in a small block is largely different than a big block. But i'd say stick with something in the above mentioned range and you should be fine. The only issue you might run into if you go with too big of a converter is it's not "all in" by your cruise rpm which can create excess heat due to slippage.
     
  6. QBuff02

    QBuff02 I like Big Blocks and I cannot lie

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    what are the cam specs at .050? and what is the advertised power band of the camshaft? Those two things play more variable into converter selection than just about anything else. Based off the advertised duration i'd venture to say it's in the neighborhood of 230ish degrees at .050. Which will put you into the area of a 2,500-3,000 rpm stall. which means You'll probably end up with a smaller than stock diameter converter right out of the gate. Lighter vehicles and smaller cube engines tend to need steeper converters as there is less resistance to acceleration. Also the torque range/curve in a small block is largely different than a big block. But i'd say stick with something in the above mentioned range and you should be fine. The only issue you might run into if you go with too big of a converter is it's not "all in" by your cruise rpm which can create excess heat due to slippage.
     
  7. Frankenchevy

    Frankenchevy . Supporting Member

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    I used a Hughes XTM towing converter. Super tight. Not built for fun, but closest I could get to being locked up from th400. Good economy and cool tranny temps though...
     
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  8. White85

    White85 Full Access Member

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    Thanks for the help guys I wasn't sure how the truck would land here considering the willys body swap. As of now I'm staying with the 3.73s for budget reasons. Duration on the cam at 50 is 234/238 and operating range is 1500-6500. I ran the numbers in an rpm calculator and it says with this setup I'll be at 1900 rpm at 60 mph. If I have a 2500 stall is it going to be slipping and building heat? Thanks again for the help guys
     
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  9. Rusty Nail

    Rusty Nail Whatever! Supporting Member

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    @60 isn't as big of a deal as @40 in many instances, which is like concerning one's self with peak numbers in a street anything.

    Without knowing the truck's intention and trying to relate to my experience , the biggest concern for durability's sake is of course, heat.
    The exchange of and transfer to.
    Heat is THE number one enemy of automatic transmissions.

    Let's talk transmission coolers first. ;)
     
  10. QBuff02

    QBuff02 I like Big Blocks and I cannot lie

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    Having a converter that's "too big" isn't an end all. Having a converter that works right for the application is key. And also, as mentioned above a tranny cooler will go a looooong way in helping protect the trans. It might also require a little discipline on your part. Like when cruising through town at slower speeds, dropping down to second manually to keep the rpm up where there's less slip at lower rpm. I have a 2,400rpm stall in my truck and when i'm between say 20-30ish mph I downshift to second so the engine is revved up higher to avoid excess slipping in the converter. I do notice a difference in the trans temp if I don't. But I haven't had any issues. I've also got 4.10's and 33" tires so my highway rpm is 2,600-2,800rpm.
     
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  11. White85

    White85 Full Access Member

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    Ok thanks guys. I have a factory trans cooler that came with the trans when I got it. It came out of a square body truck as well but don’t recall the year. I also have another one that’s new and a little larger. My main intent for the truck for now is just a cool driver, after regearing down the road I would like to do some light to moderate trail wheeling but nothing to crazy
     
  12. Frankenchevy

    Frankenchevy . Supporting Member

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    Look into Derale stacked plate coolers.
     
  13. Matt69olds

    Matt69olds Full Access Member

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    Call Coan, ATI, Hughes, etc, and have a custom converter built. The more info you can provide on your engine, trans, gears, etc the better. Keep in mind, your planned gear swap will have a dramatic effect on what converter will work best.

    a converter stall speed isn’t set in stone, it changes based on load and input torque. For example, say a converter with mild 350 with 3.08 gears has a stall speed of 2000. That same converter with a blown big block may have a stall speed of 2600, due to the added input torque. If you keep the mild 350, and put 4:10 gears in, the stall speed would probably be lowered due to the reduced load. Add huge tires, or put the engine/trans in a vehicle a thousand pounds heavier, the stall speed will change again. There is lots of science and variables that affect converter choices.

    Last argument for a custom build, most high end converter builders will allow one free stall adjustment. You could get a custom converter built for what you have now, then use the freebie stall adjustment for the planned changes when they are completed.
     
  14. White85

    White85 Full Access Member

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    Thanks guys. I looked at those derale coolers and they do look nice. I will give some convertor companies a call this week and see what they say
     

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