Low idle vac.

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    Author Topic: Low idle vac.  (Read 2893 times)

    Offline erat340

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    Low idle vac.
    « on: September 08, 2009 - 05:02:16 PM »
    Hey yall, anyone know what my idle vacuum should be generally?   Eddie RPMs, 10.2to1, Lunati 268/276...108LSA. Air Gap, Holley St. Av. 670. Cam is straight up.
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    Offline erat340

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    Re: Low idle vac.
    « Reply #1 on: September 08, 2009 - 08:37:36 PM »
    Also... 10*base timing, best vac I can obtain is 8". Checked & checked and spray tested for leaks afew times, found nothing. This thing lopes like an all out race cam! Any F B out there?
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    Offline the_engineers

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    Re: Low idle vac.
    « Reply #2 on: September 08, 2009 - 09:28:04 PM »
    I'm running a real similar set-up.  360, same compression, heads and intake.  If yours is a Voodoo cam, same stick.  I've got a 750 Holley.  Not sure where my base timing is, mech advance is 38* at 3000...probably pretty close to 10* at idle.

    I'm 12" at idle running PVC and 3 nipple breather, no power brakes.  When everything was blocked off, I was 14".

    Have you played with your idle bleed screws?  That cam shouldn't be that bad, unless you're running a 318.
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    Brooks

    1971 'Cuda 360
    2004 Infiniti G35 6-spd Coupe
    2001 Toyota Solara Convertible
    2002 GMC Savana 1500 Explorer Hightop Conversion
    1972 Dodge Dart Swinger...keeping the Slant.  Rocking the turbos.

    Offline erat340

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    Re: Low idle vac.
    « Reply #3 on: September 08, 2009 - 11:33:39 PM »
    Yeah, TE,its a Voodoo 60403.Played lots with the mix best was 8" vac Called Lunati and Holley....shoulder shruggs from both!
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    Offline erat340

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    Re: Low idle vac.
    « Reply #4 on: September 08, 2009 - 11:35:32 PM »
    Oh yeah..73 340, stock crank, pistons.
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    Offline erat340

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    Re: Low idle vac.
    « Reply #5 on: September 08, 2009 - 11:44:49 PM »
    Lunati states 13" even 12" is normal for a 60403.
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    Offline Chryco Psycho

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    Re: Low idle vac.
    « Reply #6 on: September 09, 2009 - 01:56:18 AM »
    did you degree the cam in ?
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    Challenger - You`ll wish You Hadn`t

    Offline moper

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    Re: Low idle vac.
    « Reply #7 on: September 09, 2009 - 11:49:10 AM »
    I recently tuned  a 318 with that cam. Typical 9:1ish compression, 302 heads I ported. The car when tuned had a moderately raspy idle... but it pulled 13" of vacuum at 800rpm. The stock '72-up 340 pistons yield a true compression of about 8.5:1 with a 74ish cc open chamber. The RPMs will raise that by about one point. So I think you are close to the same ratio. You should re-curve the ignition to get much more initial but keeping the total (minus vacuum) to no more than 36°. I think the magic figure will be around 18° initial.
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    Offline erat340

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    Re: Low idle vac.
    « Reply #8 on: September 09, 2009 - 12:32:11 PM »
    Thanks Neil! I just got my dial in timing light repaired. I ll try that tonite if I get time, and recheck vacuum.
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    Offline erat340

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    Re: Low idle vac.
    « Reply #9 on: September 15, 2009 - 04:06:03 PM »
    Well...ignition timing adj. anywhere made no change. Pulled V. cover re-chk preload...is O.K.  One thing I noticed is @ TDC #1 , rotor not in line with #1 manifold bolthole but more inline with #1 exh. rocker.....advance intermediate shaft gear one tooth and is parellel with centerline. Does it seem cam timing is off?
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    Offline Chryco Psycho

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    Re: Low idle vac.
    « Reply #10 on: September 16, 2009 - 02:30:44 AM »
    well the cam could be off a couple of degrees if you did not degree ti when you installed it but it will not be off far enough to see it in the dist if the car starts well
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    Challenger - You`ll wish You Hadn`t

    Offline moper

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    Re: Low idle vac.
    « Reply #11 on: September 17, 2009 - 11:43:08 AM »
    Can you post cylinder pressure readings from it?
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    Offline erat340

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    Re: Low idle vac.
    « Reply #12 on: September 17, 2009 - 11:59:57 AM »
    Yes, but I have to fly out of town for a week or so.I'll do this when I get back.
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    Offline erat340

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    Re: Low idle vac.
    « Reply #13 on: October 13, 2009 - 03:34:17 PM »
    well....tore it all apart again, see nothing abnormal. Thought....what the hell, advanced it 4* at the crank sprocket, gets up and goes over 2000rpm, still idles like crap...10" vac. Do you think this midrange Voodoo is more cam than I want?
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    Offline the_engineers

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    Re: Low idle vac.
    « Reply #14 on: October 13, 2009 - 08:24:26 PM »
    Quote from: messy on October 13, 2009 - 03:34:17 PM
    well....tore it all apart again, see nothing abnormal. Thought....what the hell, advanced it 4* at the crank sprocket, gets up and goes over 2000rpm, still idles like crap...10" vac. Do you think this midrange Voodoo is more cam than I want?
    How many cams have you had and what is the most radical cam you've driven?  I can put up with a very fussy motor, but only because I'll take the top-end trade-off.

    What is it that you don't like...the sound, the temperment or the low vacuum?
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    Brooks

    1971 'Cuda 360
    2004 Infiniti G35 6-spd Coupe
    2001 Toyota Solara Convertible
    2002 GMC Savana 1500 Explorer Hightop Conversion
    1972 Dodge Dart Swinger...keeping the Slant.  Rocking the turbos.
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