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Thread: Off idle hesitation, fluctuating idle, poor Gas milage

  1. #11

    Default Off idle hesitation, fluctuating idle, poor Gas milage

    This is what the White tech support responded with:



    "normally it comes in at 3000 and all in by 3800 the degrees depends on the motor and set up. we do not run any vac advance on our motors so I cant help with that we just plug ours off"



    I followed up asking how many degrees of advance.



    Their response is suspicious to me. This tells me that total timing would be 16 degrees until 3000 rpm which would not be right. I have 34 degrees by 2500 rpm and at steady state cruising about 46 degrees.



    We'll have to see what they say the advance is when the dizzy is at 3800 rpm.

  2. #12

    Default Off idle hesitation, fluctuating idle, poor Gas milage

    bojo wrote:

    This is what the White tech support responded with:



    "normally it comes in at 3000 and all in by 3800 the degrees depends on the motor and set up. we do not run any vac advance on our motors so I cant help with that we just plug ours off"



    I followed up asking how many degrees of advance.



    Their response is suspicious to me. This tells me that total timing would be 16 degrees until 3000 rpm which would not be right. I have 34 degrees by 2500 rpm and at steady state cruising about 46 degrees.



    We'll have to see what they say the advance is when the dizzy is at 3800 rpm.

    Agreed. Get your timing tape and set your initial with the engine warm. Then have some one watch the tach while you rev the engine to see what rpm your engine starts advancing timing (it should be almost immediate when you start to rev, you'll see it advance on the tape), and also what rpm it stops advancing (and what degree). From there you can fine tune your total timing and go for a test drive. Don't touch anything else on the Atomic side until you're sure of your timing and see how it reacts on a drive.

  3. #13

    Default Off idle hesitation, fluctuating idle, poor Gas milage

    JWZ28 wrote:

    bojo wrote:

    This is what the White tech support responded with:



    "normally it comes in at 3000 and all in by 3800 the degrees depends on the motor and set up. we do not run any vac advance on our motors so I cant help with that we just plug ours off"



    I followed up asking how many degrees of advance.



    Their response is suspicious to me. This tells me that total timing would be 16 degrees until 3000 rpm which would not be right. I have 34 degrees by 2500 rpm and at steady state cruising about 46 degrees.



    We'll have to see what they say the advance is when the dizzy is at 3800 rpm.

    Agreed. Get your timing tape and set your initial with the engine warm. Then have some one watch the tach while you rev the engine to see what rpm your engine starts advancing timing (it should be almost immediate when you start to rev, you'll see it advance on the tape), and also what rpm it stops advancing (and what degree). From there you can fine tune your total timing and go for a test drive. Don't touch anything else on the Atomic side until you're sure of your timing and see how it reacts on a drive.


    Thanks JWZ28, will do.

  4. #14

    Default Off idle hesitation, fluctuating idle, poor Gas milage

    I should have also mentioned that your IAC may need to be readjusted after setting your timing.

  5. #15

    Default Off idle hesitation, fluctuating idle, poor Gas milage

    Also vac advance should be disabled if you have it connected as it is not part of total timing. Want to see how much centrifugal advance you are getting, when it starts and stops.

  6. #16

    Default Off idle hesitation, fluctuating idle, poor Gas milage

    wade53 wrote:

    JWZ28 wrote:

    bojo wrote:

    This is what the White tech support responded with:



    "normally it comes in at 3000 and all in by 3800 the degrees depends on the motor and set up. we do not run any vac advance on our motors so I cant help with that we just plug ours off"



    I followed up asking how many degrees of advance.



    Their response is suspicious to me. This tells me that total timing would be 16 degrees until 3000 rpm which would not be right. I have 34 degrees by 2500 rpm and at steady state cruising about 46 degrees.



    We'll have to see what they say the advance is when the dizzy is at 3800 rpm.

    Agreed. Get your timing tape and set your initial with the engine warm. Then have some one watch the tach while you rev the engine to see what rpm your engine starts advancing timing (it should be almost immediate when you start to rev, you'll see it advance on the tape), and also what rpm it stops advancing (and what degree). From there you can fine tune your total timing and go for a test drive. Don't touch anything else on the Atomic side until you're sure of your timing and see how it reacts on a drive.


    Thanks JWZ28, will do.


    Thanks JWZ28, I will re-check that if I move the timing.

  7. #17

    Default Off idle hesitation, fluctuating idle, poor Gas milage

    bojo wrote:
    Also vac advance should be disabled if you have it connected as it is not part of total timing. Want to see how much centrifugal advance you are getting, when it starts and stops.

    Thanks bojo, I didn't know that and would have proceeded with it connected. Should have some numbers latter today.

  8. #18

    Default Off idle hesitation, fluctuating idle, poor Gas milage

    OK, my advance starts to move around 1,500 rpm, and that is a bit tricky because as you are coming just off idle is where the engine starts acting erratic and then it surges up quickly once you move past that area so it is kind of hard to get a good reading, then it is all in at 2,000 and 32 degrees.

    I updated all my numbers above to reflect where my setting are now. I have a steady idle now, but the off idle hesitation or stumble is still there and it seems to have lost some low end power. I could live with the loss of power if it gained me significant fuel millage. Also idle out of gear is around 900 rpm and I get some run on at that speed when I shut it down. Is there a way to lower idle speed in neutral without changing the IAC count.

    I should add that my timing was set faster then I thought, around 22 degrees, so I backed it off to 18, and that may account for some power loss. It did run fine at 22 degrees advanced and I never had any pinging issues.

  9. #19

    Default Off idle hesitation, fluctuating idle, poor Gas milage

    Just to confirm, What is the timing at idle with vac line disconnected and the rpm in park? Also you are at street setting for the cam now, does mild setting make that hesitation any better? Are you using any vac advance and if so ported or un-ported?



    Do you know what year that 350 is?

  10. #20

    Default Off idle hesitation, fluctuating idle, poor Gas milage

    bojo wrote:

    Just to confirm, What is the timing at idle with vac line disconnected and the rpm in park? Also you are at street setting for the cam now, does mild setting make that hesitation any better? Are you using any vac advance and if so ported or un-ported?



    Do you know what year that 350 is?

    Timing at idle, vac line disconnected is at 18 BTDC. RPM's at idle approx 750

    I did switch to the street setting and did a reset, but the hesitation seems to be just the same either way. I am using ported vac. The engine is a early 2 piece rear seal that I built, I was an engine builder for 30 years before I retired. I just tried swapping the vac advance to un-ported, and I can tell immediately that the stumble was gone and even a better idle, but approx 50 degrees of timing at 2500.


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