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popping and losing power above 4,000 rpms?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Ryan B., Mar 24, 2002.

  1. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    So it seems like just in the last week something is different with the way my engines running. It would wind up great all the way to 6K...
    But now it sounds like its popping just a little out the exhaust like its almost too rich or something, and losing power... revving up but not going any faster. then i'll shift it and the low and mid range power is fine.

    I'm thinking that I could have possibly blown the power valve in my holley because someone told me when you blow that its like jetting the secondaries 5-7 jet sizes richer.
    Another person told me to look down the carb and revv it to WOT and then let it return to closed and if it leaks more than a few drips out the secondaries then you've got a blown power valve.

    I was also thinking it could be ignition related too... I know people will say check the spark plugs, wires, cap and rotor.. they all seem good. I've been wanting to upgrade my ignition though!

    Someone else said to take off the valve covers and then maybe do a valve adjustment to make sure they're all adjusted properly...

    I'd appriciate Anyones 2 cents here where I should start.
    Thanks.

    350 .030" over
    Performer Rpm manifold
    Holley 600 cfm vaccuum secondaries electric choke carb
    Stock rebuilt HEI ignition
     
  2. Chaz88K5

    Chaz88K5 1/2 ton status

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    ya know 6k is a little high to be runnin that thing...i cringe when i hit 5k
     
  3. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    I once had a similar problem with high-end performance(not as high-end as you, mind you/forums/images/icons/wink.gif), and it ended up being a couple of bad wires. Off the line and in the lower range of the power band it didn't show up..........
     
  4. Thunder

    Thunder 3/4 ton status

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    I dont think it is the power valve. Is sounds like you are acually running lean on the top end not rich. I would check the jets and metering block on the secondary side of the carb There may be somthing clogging it up.
    If your power valve was bad it would run rich at idle and low RPM and get poor gas milage.
    When is the last time you did a major tune up?
    It may also be the module is the distributor is going bad. Or bad plug wires, cap and rotor..
     
  5. chevyboy24598

    chevyboy24598 1/2 ton status

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    I had the same problem, only to find out that I had my tach wired wrong.(wired in with thr MSD box)
     
  6. solowookie

    solowookie 1/2 ton status

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    easy to fix - don't run about 4,000 rpm... /forums/images/icons/wink.gif
     
  7. twenty_below0

    twenty_below0 1/2 ton status

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    6,000 YIKES...... you must have a little more done to it then you have mentioned....like the whole bottom end...LOL
    Anyway my vote goes to the ignition problems with the stock distributor your just asking for problems over 4,000 rpm's good luck
     
  8. 4x4machine

    4x4machine Registered Member

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    Once in my Trans Am, i would it up to a really high rpm, and the oil came out of my lifter becuase of the high rpm. Like your engine it would die at a higher rpm. Now i don't think that this is really quite the same situation, my $.02 anyways.
     
  9. 4x4machine

    4x4machine Registered Member

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    Once in my Trans Am, I wound it up to a really high rpm, and the oil came out of my lifter becuase of the high rpm. Like your engine, it would die at a higher rpm. Now I don't think that this is really quite the same situation, my $.02 anyways.
     
  10. chevyboy24598

    chevyboy24598 1/2 ton status

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    Whats the problem with reving a SBC over 6 grand? The one thats in my truck now has 10,000 rpm potential. As it was in a drag car.
     
  11. DesertDueler

    DesertDueler 1/2 ton status

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    I doubt you motor has any power at 10,000 rpms though /forums/images/icons/smile.gif I wouldnt take a stock SBC chevy over 5,000 rpms. Even on modified small blocks I dont like going over 6,000 rpms. My firebird Doesnt see over 6,000 and it runs high 10s in the 1/4
     
  12. chevyboy24598

    chevyboy24598 1/2 ton status

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    Does your firebird have a small block? I doubt it.... Most race proven SBCs dont make good power until 6 grand. As of now I have a 7,000 chip in my MSD box and it feels like it would keep pulling until at least 9,000. The secret of building a motor is to match the rockers with the cam with the valve
    springs. BTW this is really off topic to what he asked.
     
  13. solowookie

    solowookie 1/2 ton status

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    this isn't nascar
     
  14. NoSmog73

    NoSmog73 1/2 ton status

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    Hey ryan just a ??? Whacha ya doing going to 6k.. I know that you can jump, but wait are you trying to make a new burnout video that I can see...lol...
     
  15. 4x4machine

    4x4machine Registered Member

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    I'm not saying a high rpm is bad, it just depends on what your engine is built for, what parts you use, if its balanced etc. My post wasn't very clear. This just happened once, but the oil in my lifter came out, and it took a while for it to gain back the oil pressure (as a result wouldn't push rocker as far resulting in less lift). And until the pressure was restored, the engine would cough and die at a higher rpm, but was fine from then on. So it just took a few minutes to restore pressure, and now it's good to go.
     
  16. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Thanks for the responses...

    I said it would wind great all the way up to 6,000... not meaning i would wind it up that high very often at all...
    I have rarely taken it past 5,500 rpms... but i know it has been to 6K out in the sand dunes in 4 low. It has a 'vette cam in it so it tends to kick in on the top end more than anywhere else... until recently.

    What i was really saying is that it has never had any problem winding up that high or anything past 4K... and it just seems recently that it's running different on the topend.

    I appriciate all these comments and gives me ideas to look over and consider what it could be. Keep the ideas comin'.
    I'll get back to ya with another post if and when i find out what the hell is goin on here.

    But you're right ya know... if i just don't take it past 4,000 it's not really a problem. /forums/images/icons/smile.gif
     
  17. 84_Chevy_K10

    84_Chevy_K10 Banned

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    "6,000 YIKES...... you must have a little more done to it then you have mentioned....like the whole bottom end...LOL"

    My truck hit 6,000 RPM with the headers open in the mud pit at our competition last year. The crowd loved it, and it still ran fine afterwards.

    Stock bottom end, too. It has hit over 5,000 many times, but I was just a little scared to see 6,000 in the pit.
     
  18. DesertDueler

    DesertDueler 1/2 ton status

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    Actually its a pontiac 350 /forums/images/icons/smile.gif
     
  19. bigmack

    bigmack 1/2 ton status

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    My truck see's 5000-6000 rpm's on a regular basis, mainly spinning in the mud. The first thing that comes to my mind is the cam. If it has seen alot of miles then the lobes may be getting wore down therefore not letting it rev to its potential. Also have you checked your timing ? Just a couple of thoughts.
     
  20. twenty_below0

    twenty_below0 1/2 ton status

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    I have too seen a stock 350 do this but habitually is another point, your stock bottom end wont do it that many times in a row for very long with out a lot of problems!!!! It's a well known fact that to built a consistent 6,000 rpm 350 it takes more than stock parts....and a little more money about 500.00 for parts alone if your lucky....real lucky, once every now and then is one thing but continually is another....this is my point nothing more!!!
     

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