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Cam advice

Discussion in 'The Garage' started by shimniok, Dec 18, 2004.

  1. shimniok

    shimniok Registered Member

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    I'm trying to find some cam advice and figured if anyone could help the Chevy folks could. :) I'll come clean and admit I don't really have a Chevy but let's pretend I do and hope you can forgive me :D

    Given: 5000# vehicle, 400cid Chevy, GM TBI, performer intake, 33" tires, 3.73:1 gears, low stall, 3spd tranny, runs 2600-3000 hwy rpms; 2600 @ 65mph. Goal: haul gear, people up I-70 passes in 3rd with power to spare for a 4000# trailer someday.

    What kind of cam and compression ratio would you pick? I still have to pass stringent CO dyno emissions. I have Desktop Dyno (DOS) so full cam specs would be really helpful. Also do you have factory cam specs for 400cid motors in heavy trucks?

    thx!
    Michael
     
  2. 84_Chevy_K10

    84_Chevy_K10 Banned

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    TBI is your limiting factor.

    9:1 and the biggest computer friendly grind you can find, which is 212 @ .050" or so.
     
  3. POWERMAD

    POWERMAD 1/2 ton status

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    TBI and 400 is not a good mix IMOHO.
    The TBI is a noose around it's neck.
    If a TBI plant is your goal I would stay in the 350 range.
    Most cam grinds out there are based on a 350.
    That would be sorta like dropping in a 454 and putting a 2 barrel manifold and carb to get good mileage.
     
  4. 84_Chevy_K10

    84_Chevy_K10 Banned

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    :confused: :confused: :confused: :confused: :confused: :confused: :confused: :confused: :confused:

    A 2 barrel carb is going to get horrible mileage compared to a 4 bbl.
     
  5. POWERMAD

    POWERMAD 1/2 ton status

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    My point exactly.
     
  6. shimniok

    shimniok Registered Member

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    Ok, forget I said TBI. :) Let's forget the induction system. That isn't what I'm after. I'm trying to build up a motor, I'll bolt on whatever I need to. :)

    I want to try and figure out what kind of grind best fits given the tall gears, low rpm's, big vehicle weight, and 3spd constraints...

    I could put a race cam in there if I wanted to and have all the hp I want, but in a very heavy vehicle with auto trans it's going to be a nightmare to drive in the city and torque in my cruise rpm of 2000-3000 will be abyssmal...right? I could put in an econo grind, but will the motor will have nothing above 3500rpm?

    many thanx
    Michael
     
  7. POWERMAD

    POWERMAD 1/2 ton status

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    Why build a 400 for a 350 CI parameters?
    TBI is the limiting factor is it not?
    All of the advantages of more cubes which will take a bigger cam and running a bigger cam allows the use of higher compresion.
    are lost on TBI.
    Clearer translation now?
     
  8. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I agree with you that TBI is not ideally suited to deal with a 350, but on the other hand, while you may not have optimal 4000+ RPM performance, I bet it'd still have quite a bit more low end torque than any 350 and with a few mods, I'm sure it'd run just fine.

    If it was a race car, I'd say no, too much power lost in the buildup. Seeing as how it's a truck, I don't think making that last 20 ft/lbs matters anywhere nears as much as the fact that it will still run when it's halfway on its side or has a heavy trailer behind it and is lugging down. :D
     
  9. POWERMAD

    POWERMAD 1/2 ton status

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    Alrighty then we have some parameters to work with.
    The first part of ant build is determining what it will be used for.
    Extermly heavy? what's that?
    If this a paper project dump the SBC and get to business with a BBC.
    If ya actualy had something to work with it would make suggestions easier.
    From the do it right the first time scenario... build a BBC
     
  10. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    That would be pretty tough to pull a 4K trailer up a hill in 3rd gear if the passes on I-70 are like some of the hills I have heard are in Colorado. It would take one radical 400 to do that. Even a built BBC would have a little bit of trouble maintaining around 50mph(3rd gear) with a trailer weighing 4K in the Co mountains.

    i would carb the motor, cheaper and capable of providing the apropriate power building fuel, especially in the higher RPM range that you could need for pulling in 2nd gear. I have a comp cams 268H cam. 454" lift in and out and 218 duration. There are better cams out there but I like it and works well in my 400.
     
  11. shimniok

    shimniok Registered Member

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    Ok, thanks for the input. I'm trying to understand what's realistic. I can live with slower speeds with the trailer attached. No prob.

    So if I'm going to struggle with the trailer, I at least I want to run 75mph with ease in 3rd with JUST the truck, 4 people, and camping gear (call it 5500#) with 3.73's, 33"s, and 3spd auto.

    Is it even possible to build a 400cid thumper motor that builds 400+ lbs-ft of torque below 4000rpm to solve this problem?

    Or is a better answer to build max horsepower from 4000-5500rpm and rely on 2nd gear in the hills?

    Michael
     
  12. SUBFAN

    SUBFAN 1/2 ton status

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    Good heads, exhaust, and intake can give you a 500 ft lb and 450 hp....400 SBC....

    I would opt for better gears too....

    A BBC or CTD would be easier to live with, and prolly last longer....

    As for smog legal, well I can't help you there. Cheapest of the three options would be to build a BBC, and keep an eye out for a T 400 trans. w/a big cooler.... :waytogo:
     
  13. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Once again I think your hopes are a little high. 75mph is a lot even without a trailer. You will probably be heavier than 5,500 pounds with a few people and a bunch of gear. You would need one hot 406 to be able to do that...big enough to where it sucks premium fuel along with octane booster and in a much faster manner than you would like. It just would take too wild of a cam and compression to make that kind of power that would actually usefull pulling hills.

    My mild 406 makes about 400ft lbs at the crank and starts in around 3K+. It makes good torque but I bet it would have a hard time managing 65mph in those nasty CO hills empty.

    I would build a mild 406 and be happy with 55mph up a hill at say 6K or I would swap to a bombed cummins. A cummins is about the only engine besides a nasty fuel drinking blown stroker big block that will pull hills without dropping below 65mph with or without the trailer.
     
  14. shimniok

    shimniok Registered Member

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    Thanks for the info. I really appreciate everyone's help. Earlier when I said I didn't have a Chevy I meant I had another non-Chevy vehicle. :)

    Sounds like the Chevy motors can be built to put out sick power just like I've always read. Of course if I had a Chevy truck I'd run a 454. :)

    Since I have a J*** (a four letter word around here I guess) Grand Wagoneer the current 360 is a dog, especially from idle to 2500. A buddy has similar rig with taller gears and dusts me up hills I can barely pull 60 on. His AMC401 has high CR and stock cam. I wanted to emulate this.

    But I was debating whether to do an econo grind that puts 450 lbs-ft at 2000 and drops off like a rock from 3500 up or an Edelbrock Performer or similar that runs over 430 lbs-ft 2000-3500 and 320 hp @ 4000.

    I figured I could learn based on what grinds Chevy trucks with 400's ran. Sounds like a good strategy in that case is to build for a 3000-5500rpm power band and use 2nd for the hills where needed.

    Michael
     
  15. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    I think you are on the right track. I would build it to make good mid range power.
     

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