holley 650dp again

Discussion in 'Troubleshooting & Diagnosis' started by lone_anarchist, Dec 3, 2009.

  1. ok now im kinda confused. after doing the fix for the transfer slot now the car is running lean lol right now there are 59 jets in the primaries and i cant remember on the secondaries but under full throttle the AFR runs at about 13.5. under 1/2 throttle it is about 15-16. light throttle is 14-15 and under almost no throttle at all it goes to 13-14 and idle at 12-13. the car feels like its about to die off at 1/2 throttle and i am still hearing a hiss almost washy sound only at 1/2 throttle "same noise i heard with the other carb. i cant find any damn vacuum leaks. very confused at what route i need to go.

    previously before this i had 55 jets in it and there was a good increase in richness when i put in the 59's

    when starting the car after being warmed up it, it is hard to start but will start with no help. once it starts it idles really low until i give it a tap on the gas pedal.

    i dont know if exactly what it was but it sounded like there was a clear whistle noise that was on and off maybe 1-2 times every minute near the upper part of the engine. was very strange but this noise went away after the jet swap.
     
  2. Bikefixr

    Bikefixr Veteran Member Lifetime Gold Member

    1,643
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    Mar 13, 2006
    ok now im kinda confused. after doing the fix for the transfer slot now the car is running lean lol right now there are 59 jets in the primaries and i cant remember on the secondaries but under full throttle the AFR runs at about 13.5. This is Lean? It's a bit fat. 14.7:1 is ideal. Max power comes at about 13:1. You're right there. under 1/2 throttle it is about 15-16. OK, maybe a touch lean, but not for street driving, really. light throttle is 14-15 and under almost no throttle at all it goes to 13-14 and idle at 12-13. Ok, so at dead-idle it's a bit fat. At light throttle is a a bit fat at 13-14:1. the car feels like its about to die off at 1/2 throttle It's a bit lean thereat 15-16:1 and i am still hearing a hiss almost washy sound only at 1/2 throttle "same noise i heard with the other carb. i cant find any damn vacuum leaks. very confused at what route i need to go. I'd add 2 steps to the primary jet size and go down 1 size on the secondaries. take the power valve from a 6.5 to a 7.5, or even a 2-step valve with 10.5 and 6.5 stages. This will fatten up the mid-throttle a bit without making WOT too fat. previously before this i had 55 jets in it and there was a good increase in richness when i put in the 59's Sure, 4 sizes equals about 12-13%.

    when starting the car after being warmed up it, it is hard to start but will start with no help. once it starts it idles really low until i give it a tap on the gas pedal. By tapping the pedal you are setting the throttle blades from total close to the fast-idle step. Normal.

    i dont know if exactly what it was but it sounded like there was a clear whistle noise (vacuum leak) fthat was on and off maybe 1-2 times every minute near the upper part of the engine. was very strange but this noise went away after the jet swap. When you took the carb off and played with it, you fixed the leak inadvertantly.
     
  3. wow you were on top of that :rolleyes: well i understand that full throttle is basically on the money, didnt mean to come off like i was saying that was lean. and the whistle noise was weird, it didnt come off like a vac leak. it sounded like a bird or a whistle you can make with your mouth. as for the mid throttle lean it seems to come on the second that noise "hiss washy" sound comes on, the second i hear that i watch the AFR drop to lean zone and even sometimes falling off the reading to the point were it doesnt read. i think my power valve right now is a 6.5. and seriously thank you so much for the help
     
  4. ok my local napa is the only place that has anything close. they have 4.5/5.5/6.5/8.5 but they dont have 7.5 would an 8.5 work? or you think that would be to much
     
  5. PaulyNY

    PaulyNY Member

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    Sep 20, 2009
    buffalo, NY
    whats your vac reading in gear at idle?
     
  6. im about to check that right now, i had broken a bolt holding my throttle bracket on lol had to custom fit a new one on.
     
  7. my gauge was bouncing quite a bit between 15 and i guess 14 or 13 cant count out how they are labeling each line lol. and also tried somthing different by closing the choke a little bit it actually ran great. and almost cleared up mid throttle perfectly. i took some videos of the AFR if anyone is interested in it :p the quality isnt good though and the sound of the car muffles out my voice

    but if im taking in my own information by the choke deal, that means i need more fuel. :p and a 7.5 power valve because of the 15/2 is tada 7.5
     
  8. i also forgot to mention i heard the whistle noise again. and it is the carburetor and sounds like its coming from the venturi area but this time it was a consistent sound until throttle was provided :)
     
    Last edited: Dec 4, 2009
  9. Bikefixr

    Bikefixr Veteran Member Lifetime Gold Member

    1,643
    20
    Mar 13, 2006
    whistles = vacuum leak. Have someone spray some carb cleaner around the baseplate, metering block junctions and throttle shafts when you hear that noise. You'll find it fast. Go to the 7.5 PV and drive it. If it goes in the right direction, then change jets. Remember, the idle system on Holley carbs is active all the way up to about 2500 RPM. The main system starts up about 1500, and from about 1500 to 2500 it's a combo of the 2 systems. Then the PV opens to enrichen as the primary circuit gets up to full capacity. I always liked to tune for Idle at about 15.:1, light cruise at 16:1, mid-throttle at 14.5: and WOT at 13:1. I'd purposely set the primary side lean and use the secondaries to compensate at WOT. My 650 DP in a '73 Monte Carlo, 350 with LT-1 cam, headers, ported 291 Heads etc..and a 3:23 reargave me 24 on the highway all day long, passed NJ smog easily, and still clicked mid 13's. Took time and a few screw-ups, but it's doable. Work on 1 part of the carb at a time. Find and fix that leak.
     

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