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  •  » TUNING PROBLEMS !!

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    8/23/2019 8:18 PM  #1

    Vkt-66
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    From: Bedford, Tx..
    Registered: 7/22/2013
    Posts: 142

    TUNING PROBLEMS !!

    Tuning problems
    289 T-5 Trans 10.0 to 1 roller Cam ( .533 lift  x 224 duration  - lob lift  3330 - lob separation 110.0 )  and roller rocker assembly gt 40 heads Hooker long tube headers
    performer intake Holley 650 dual pump msd 6-a msd Blaster 2 coil motorcraft distributor ( pertronix elect. ignition )
    curved total comes in at 2750 rpm
    Timing set 12ﾟ base
    24ﾟ mechanical
    36ﾟ total mechanical plus Base .. Total with vacuum 46ﾟ( haven't  tested on road  yet ) 

    Here's my dilemma when trying to adjust my carburetor I get it warmed up and when it reaches 180ﾟ
    I tune to get around 800 rpm Adjust idle mixture screws 4 total turns out With around 7 or 8 inches of vacuum off manifold . that's the best I get ....way to far out !!!
    But it will not hold a steady idle seems to fluctuate 150 rpm then sometimes totally die ...
    even when idle adjusted to 1,000 rpm 

    I did put a 3.5 power valve In it as per Holley Tech suggested when I called them about drilling those small 3/64" holes in the throttle plate ?? ( Holley Tech said not to )

    or what about wires - spark plugs  ?? did check two plugs look great !!
    pulled each wire individually from cap ,,, it would still start with a little more throttle  one dead cylinder .. just to check if getting spark and or wires were bad ...  

    I do feel there's a lot of vacuum being sucked down the main throttle of the carburetor..,
    maybe I do need to drill the throttle plates 

    ​Or is there something else in my timing that I'm not catching ??  HELP  !!!!


     

    66 PonySilverBlue-289/gt40/roller/650cfm/ram air-T-5-cable-w4way.disc/4-245x50x16"
     

    8/23/2019 10:16 PM  #2

    TKOPerformance
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    From: Newark, DE
    Registered: 12/15/2014
    Posts: 7,522

    Re: TUNING PROBLEMS !!

    Need some more info.  Did it run good before and stopped?  If so what was changed? 

    That doesn't sound like a lot of vacuum, but that cam is huge for a 289, so maybe that's normal?  To put it in perspective, the cam Crane's tech department sold me for my 331 has less lift and a wider LSA.  Its going in an engine that's 42 cubes larger and is intended to make 425-450HP at 6,500RPM, yet still have enough vacuum to run power brakes.

    On the surface it seems like a lot of cam for a 289 with GT40 heads.  Even with a spring upgrade I don't see the GT40s flowing enough stock to support the RPM a cam this big is going to need to achieve max power, which on a 289 is going to have to be 7,000+RPM.

    You can't expect much idle under those conditions, and I would venture a guess that 800RPM is too low. 

     

    8/24/2019 9:10 AM  #3

    DC
    Senior 24-7 FYI Addict

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    From: Marshall, MI
    Registered: 4/01/2013
    Posts: 1,251

    Re: TUNING PROBLEMS !!

    Your set-up is not far from what I have on one of mine. I do have a 600 cfm double pumper on it and it has the holes in the throttle plates. It starts and idles really good. I got the carb from Pro Systems, it came with the holes in the throttle plates.

     

    8/24/2019 11:38 AM  #4

    RV6
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    From: Pine Junction, CO
    Registered: 3/01/2016
    Posts: 1,250

    Re: TUNING PROBLEMS !!

    Once your start cranking the idle up the throttle plates move and you may have uncovered the idle/transfer slot. One method of adding air is to open up the secondary plates just a little. There is a stop screw on the bottom of the carb to do this. This is adjustable, holes in the main throttle plate are not. 

    Gary Zilik - Pine Junction, Colorado - 67 Coupe, 289-4V, T5
     

    8/24/2019 12:08 PM  #5

    Vkt-66
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    From: Bedford, Tx..
    Registered: 7/22/2013
    Posts: 142

    Re: TUNING PROBLEMS !!

    OK guy's As far as my idling problems our concern it's been doing this since starting this engine up I 1st had a 600 cfm vacuum advance that I tried to adjust but couldn't so then I went to the 650 because after I talked to Holly they said my Cam was not that radical and because I had a manual transmission I could use a 650 cfm. 
    So now that I'm thinking it's just a vacuum condition from the carburetor and  Cam  I'm in the process of increasing the secondary idle speed screw ...

    I'll let you now the results in an hour or so !!  THANKS

    66 PonySilverBlue-289/gt40/roller/650cfm/ram air-T-5-cable-w4way.disc/4-245x50x16"
       •Thread Starter
     

    8/24/2019 12:27 PM  #6

    6sally6
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    From: Surfside Beach,SC
    Registered: 4/02/2013
    Posts: 6,868

    Re: TUNING PROBLEMS !!

    Try this........give it MORE initial advance. Then slow down the curb idle(it should increase with the added initial) and screw the screws in until it starts to shudder and back out until it cleans up. Do the same on both sides. Then slow the idle down and try it.
    I KNOW they are all different butt....mine is a 5.0 with a roller cam. 230/236 @050 with an LSA of 108* and it idles at 700 RPM nicely. With open headers! Thru the mufflers....it seems like it needsa little more RPM to work.
    Been so long since I had it capped off!!
    6sally6

    Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
     

    8/24/2019 2:12 PM  #7

    Vkt-66
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    From: Bedford, Tx..
    Registered: 7/22/2013
    Posts: 142

    Re: TUNING PROBLEMS !!

    Opened the secondary idle plates  It was a little better
    Added a little more initial timing That helped a little
    but what helped the most is that I capped off the PVC  Vacuum line and let the valve cover breathe  No longer takes a dump and Dies on me ....

      And then just for good measure my lower radiator hose decides to develop a leak !!

    66 PonySilverBlue-289/gt40/roller/650cfm/ram air-T-5-cable-w4way.disc/4-245x50x16"
       •Thread Starter
     

    8/24/2019 3:49 PM  #8

    6sally6
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    From: Surfside Beach,SC
    Registered: 4/02/2013
    Posts: 6,868

    Re: TUNING PROBLEMS !!

    I had to put a "reducer" in my PCV line too! Still have vacuum/suction to PCV just not as much. Try closing up the secondary idle with the PCV disconnected and see if its "better". Would be best to do it all with the initial timing.
    Big 'snotty idling' camshafts respond well to a pile of initial timing. 14-18* initial is NOT too much. Just don't want to exceed 36-38* total timing. Butt-chew already know that probably.
    This is assuming you have NO vacuum leaks!  Vacuum leaks screw everything up.
    6sally6

    Welcome to the BIG-BOY camshaft club!

    Last edited by 6sally6 (8/25/2019 3:01 PM)

    Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
     

    8/24/2019 4:17 PM  #9

    RV6
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    From: Pine Junction, CO
    Registered: 3/01/2016
    Posts: 1,250

    Re: TUNING PROBLEMS !!

    Vkt-66 wrote:

    but what helped the most is that I capped off the PVC Vacuum line and let the valve cover breathe No longer takes a dump and Dies on me ....

    And then just for good measure my lower radiator hose decides to develop a leak !!

    Those little PCV valves don't like modified engines. A restrictor like Sally has may be in your future.
     

    Gary Zilik - Pine Junction, Colorado - 67 Coupe, 289-4V, T5
     

    8/25/2019 11:21 AM  #10

    Kevin197
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    From: Connecticut
    Registered: 4/02/2013
    Posts: 47

    Re: TUNING PROBLEMS !!

    That seems like awfully low  vacuum for that camshaft. That and the backed out idle mixture screws sure seems like a vacuum leak to me......

     

     

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