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Won't Get up and go

Discussion in 'Chevy Trucks' started by ejaime23, Jul 16, 2003.

  1. ejaime23

    ejaime23 Junior Member
    from Texas
    Messages: 6

    Hi there guys, I'm just wondering if I could get some info from all you hot rod enthusiasts out there. I have an '81 Silverado with a 4-bolt 350. So far, I've put a Crane Energizer cam, 1.6 Magnum roller rockers, Flowtech headers, Purple Hornies mufflers, and Holley Dominator intake with a 4160 600cfm carb. It has a TH350 tranny with a 2600 stall converter and a shift kit. The problem is it's not givin' me anything. I feel like all my time and money has gone to waste. Now, my rear end is currently a 12-bolt with a 3.07 ratio, I'm in the process of changing that to a 3.73. Do you guys think that's what's holding my truck back or did I make a wrong move somewhere? Thanks in advance for all your help!!
     
  2. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    Edgar,I used to do the same thing you are looking for power. truck is too heavy,engine too small for serious power. The gears will help a lot. I think 2600 is to high for a truck,2200 stall is more than enough. when you want serious power in a pickup,buy yourself a used 94-02 Cummins diesel Dodge Ram,and give me a call,you wont be dissapointed:D .
     
  3. Chuck Smith

    Chuck Smith 2000 Club Member
    from NJ
    Messages: 2,317

    Is that Holley Dominator a single plane intake manifold? If it is, there is your problem. Depending on tire size, I would go with 4.11 gears instead of 3.73's. If you are going to run 33's or larger, the 4.11's will give you more power off the line.

    ~Chuck
     
  4. wyldman

    wyldman Member
    Messages: 3,265

    The Holley street dominator is a high rise dual plane design,and should work well.The 600 CFM holley will give good throttle response too.

    Gearing will help,3.73 minimum,depending on tire size like Chuck said.

    What are the cam specs,as it may be a little too large for a big heavy truck.Was it degreed properly when installed ? Advancing the cam 4 degrees may help in your application.

    The 2600 stall convertor is too loose,unless it's a drag only truck.Stall speeds are very dependant on HP,vehicle weight,convertor manufacturer,etc,so tune the motor the best you can first,and get the right gear ratio,and then see what your actual stall speed is.It might just be OK.

    I think your biggest problem may just be tuning.Using the correct plugs,cam timing,igniton timing and advance,and carb setup are crucial to make it all work.

    You should be using R43TS plugs,gapped at .065-.080.AC Delco plugs only,no fancy aftermarket crap.

    Double check the cam timing,and degree it in straight up to start.If you find after tuning it that it's still a little doggish off the line,you can advance it some later.

    Lifter\valve adjustment can affect power too.Back them all off (hot),and go down until you have no play,then one full turn extra.This will give you more bottom end.

    Get an advance curve kit installed.You want at least 12-14 initial timing,with the advance coming in as quick as possible just off idle (900-1000 rpm or so).All advance should be in by 2000 rpm,with a total advance of 40-42.You can go as aggressive as possible on initial,advance,and total to the point where it just starts to ping,then back it off a hair.Do all setup with the vacuum advance disconnected.

    Hook your vacuum advance up to a ported vacuum source at the carb (no vacuum at idle,starts to build off idle).Run as much vacuum advance as the engine will tolerate with out pinging at light throttle.You can control the pinging by using an adjustable vacuum advance,or give it more throttle.This type of advance tuning will give you really good gas mileage.It can be done last,after everything else.

    Stay away from Accel super coils,only use a good Delco OEM coil.An MSD box will really help too.

    Lastly,you need to set the carb up.Accelerator pump cam will probably need to be moved to the number 2 hole,as you need a good pump squirt to get a heavy truck moving.You can then tune using different jets,and secondary valve springs to get better acceleration.Baseline jetting should be 68 primary.Stock is 65 or 66.The secondary is not adjustable on a 4160,it has a fixed plate.I wouldn't worry about that yet.Get the primary jets,and secondary air valve tuned first,and you should be happy.

    Final adjustments,like idle speed and mixture should be done after every other adjustments.Turn the mixture screws in until you get a lean surge,and then slowly back out until the engine smooths out,and pulls the highest vacuum.Double check with truck in gear.

    HP books has an excellent book on tuning Holley carbs.Get one,it's a good read,and will help you out.


    If you have any more questions,just ask.
     
  5. ejaime23

    ejaime23 Junior Member
    from Texas
    Messages: 6

    Hey there thanks a lot guys for the info. The Holley Dominator is a dual-plane manifold, I picked the dual plane to give me power at the low end of the RPM scale. I plan to make this my daily driver that can also turn heads so I don't wanna put anything past a 3.73 gear size because I want to be able to go past 70mph. I hear those gears really have your engine winding pertty hard when you get them past 50mph. Thanks a lot guys!!
     
  6. ejaime23

    ejaime23 Junior Member
    from Texas
    Messages: 6

    Hey there thanks a lot guys for the info. The Holley Dominator is a dual-plane manifold, I picked the dual plane to give me power at the low end of the RPM scale. I plan to make this my daily driver that can also turn heads so I don't wanna put anything past a 3.73 gear size because I want to be able to go past 70mph. I hear those gears really have your engine winding pertty hard when you get them past 50mph. Thanks a lot guys!!