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Thread: I am desperate need of help.

  1. #1
    Dominator Scott
    Okay here is the deal. I recently bought a tunnel ram with dual Holley 600's for the BBF 460 and I am having a hell of a time tuning it in. (LEAN CONDITION)
    The 460 is relatively stock to the best of my knowledge but may have a mild cam shaft. The only other modification is the Weiand tunnel ram and Hooker over transom headers. The carbs originally had 66 jets in the primaries and 67 jets in the secondaries with a 7.5 power valve which was too lean, so I upgraded the jets to 72's in the primaries and 75's in the secondaries with a 3.5 PV. I also installed a Holley 110gph mechanical fuel pump and installed 1/2" stainless braided fuel lines and pickup's. Fuel pressure is at 7psi,the timing is spot on at about 32 degrees,fuel filter is clean, but at 4600RPM's she stumbles and sputters from a lean condition. I have ordered rear metering blocks for the carbs and intend on jetting the snot out of it. 77's in the primaries and 83's in the secondaries but I just want to make sure I am on the right track.
    I should add that jetting the carbs up,switch to the 3.5PV and new fuel pump has helped the lean condition but at 46ooRPM's she still falls off and sputters which sucks because I still have a 1/3 throttle left to go.
    PLEASE HELP!!!!!!

  2. #2
    squirt'nmyload
    i had this same problem when i switched carbs....put 78's in the front and 80's in the back...got much better but problem still existed....took off the big spacer(2 or 3 in) that was on the new carb(didn't have one on before)..... problem went away

  3. #3
    Dominator Scott
    i had this same problem when i switched carbs....put 78's in the front and 80's in the back...got much better but problem still existed....took off the big spacer(2 or 3 in) that was on the new carb(didn't have one on before)..... problem went away
    I assume you mean that you had carb spacers and then the tunnel ram under them? No carb spacers hear. It does however blow my mind that I am running lean with dual 600's when originally I was running an 800 double pump and a "Torker" intake and plug reading were about perfect.
    I thinking it's gonna take stepping up from 72's to 77's in the primaries and from 75's to 83's or 84's in the secondaries on these carbs.:jawdrop: Here I thought dual carbs was gonna be too much for this engine. Boy was I wrong!!!!
    So you guys think I am going in the right direction with bigger jets,or is there something I could be over looking causing the lean problem?

  4. #4
    squirt'nmyload
    I assume you mean that you had carb spacers and then the tunnel ram under them? No carb spacers hear. It does however blow my mind that I am running lean with dual 600's when originally I was running an 800 double pump and a "Torker" intake and plug reading were about perfect.
    I thinking it's gonna take stepping up from 72's to 77's in the primaries and from 75's to 83's or 84's in the secondaries on these carbs.:jawdrop: Here I thought dual carbs was gonna be too much for this engine. Boy was I wrong!!!!
    So you guys think I am going in the right direction with bigger jets,or is there something I could be over looking causing the lean problem?
    i should've said that i didn't have a tunnel ram. went from a 750 vac sec. to a 850 dp that had a spacer on it.....i'm no expert but jet it up and see what happens!!!

  5. #5
    Dominator Scott
    i should've said that i didn't have a tunnel ram. went from a 750 vac sec. to a 850 dp that had a spacer on it.....i'm no expert but jet it up and see what happens!!!
    Jetting the chit out of it was the only think I can think of considering I have checked or upgraded the entire fuel delivery system. I thought maybe it was ignition but it ran fine with no sputtering before the tunnel ram was installed.
    Also there isn't any vacuum leaks that I can find because she purrs at 900RPM's and doesn't miss a beat.

  6. #6
    058
    Power valves do not increase or decrease fuel mixture, just the timing [vacume] when they will open. By switching to a 3.5 from a 7.5 that means the p/v will discharge extra fuel at 3.5" of manifold vacume. The 7.5 p/v will discharge extra fuel at 7.5" of manifold vacume. What controls the extra fuel from the p/vs opening is the power valve channel restriction [pvcr] These are the small holes you see when the p/v is removed. I suspect your lean condition is from the system itself. You say you installed 1/2" line, does that include an internal 1/2" tank pick up as well? Did you eliminate the tank check valve? Carbs do not know what engine they are on or do they care, they only respond to vacume and air flow. Jetting up will not cure your problem. You need to check fuel pressure at WOT and maximum load, my guess is the fuel pressure is dropping at WOT. The origional jetting should be close but I would jet up to 73-74 in the secondary side and leave the primary at 66.How old are the carbs? It could be they need to be rebuilt and have warped metering block surfaces on the main carb body. One more thing, are you running the Holley pressure regulator[s]? If so how many? one or two?

  7. #7
    Dominator Scott
    Power valves do not increase or decrease fuel mixture, just the timing [vacume] when they will open. By switching to a 3.5 from a 7.5 that means the p/v will discharge extra fuel at 3.5" of manifold vacume. The 7.5 p/v will discharge extra fuel at 7.5" of manifold vacume. What controls the extra fuel from the p/vs opening is the power valve channel restriction [pvcr] These are the small holes you see when the p/v is removed. I suspect your lean condition is from the system itself. You say you installed 1/2" line, does that include an internal 1/2" tank pick up as well? Did you eliminate the tank check valve? Carbs do not know what engine they are on or do they care, they only respond to vacume and air flow. Jetting up will not cure your problem. You need to check fuel pressure at WOT and maximum load, my guess is the fuel pressure is dropping at WOT. The origional jetting should be close but I would jet up to 73-74 in the secondary side and leave the primary at 66.How old are the carbs? It could be they need to be rebuilt and have warped metering block surfaces on the main carb body. One more thing, are you running the Holley pressure regulator[s]? If so how many? one or two?
    Fuel pressure is at a constant 7lbs and no it isn't a Holley regulator. I believe it is a Aeroquip (1 regulator) and it came with the tunnel ram as did the carbs.
    As for the tanks it appears these saddle tanks have 1/2 inch pickups in them because the original fittings were 1/2 inch on the tank side and tapered down to 3/8's on the fuel line side. Now it is 1/2 all the way through. As for the check valve I'm not sure if there is even is one in the tanks and if there is how do you get to it.(Pickup tubes are welded into the tanks and then the pickup itself threads in to it.)
    I am at a higher jetting now than what you are recommending and she is still lean. I have talked to a couple people who have run tunnel rams before and was told not to be surprised if I need to jet into the high 70's on the primaries and low 80's jets in the secondaries. Also all bowl and metering block gaskets have been replaced on the carbs.

  8. #8
    QuickJet
    Check your float level and re-check the pressure with another gauge (just in case).
    058 is dead on with the jetting. There is no need for those 600s to require that much jetting.

  9. #9
    Dominator Scott
    Check your float level and re-check the pressure with another gauge (just in case).
    058 is dead on with the jetting. There is no need for those 600s to require that much jetting.
    Rechecked float level on Saturday's run and it dead on. gauge is a brand new liquid filled gauge that I just bought. I will check it though.

  10. #10
    QuickJet
    What do the plugs look like? Are they pretty much uniform or are some darker than others.
    Looks good by the way.
    http://***boat.com/forums/attachment...8&d=1179777540

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