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  1. #1
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    Default Spark Plug reading for tuning

    Gday

    Just wondering if someone who is good at reading plugs can read my plugs. I have the car tuned up pretty well its driving real good. These are old spark plugs so try to ignore the porcelain fowling I beleive once i put new plugs in this will be rectified. Im still getting a bit of black at the ground strap bottom would this mean carb overjetted? The ring also shows black. The rest of the ground strap seems pretty fine though can anyone tell roughly what my timing would be from the plug?

    these are 6 heat range plugs also im going to try 5?
    IMG_0169.JPGIMG_0177.JPGIMG_0172.JPG
    Last edited by bfhoon; 14-01-2019 at 09:23 PM.

  2. #2
    Do you ever leave? DR327VK's Avatar
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    IF it has mildish cam eg 286, looks ok to me. try 5 looks like it could handle it
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    Do you ever leave? EH179's Avatar
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    Try the 5's and lower timing 2 deg. leave the jets as is and check again after a hard run, not after idling for 10 mins.

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    I dropped 2 degree timing in it I reckon im around 15 to 18 degrees it moves around a tad. So do you think these plugs look ok? Stuffing around with it again and I fouled them all up again. One thing that is really shitting me as I have my curb idle wound in about 2 full turns to get it to idle at 850 to 950 rpm this is way to much isnt it? My idle air restrictor screw ar eonly turned out half a turn anything more and vacuum goes crap. I even tried cracking open the secondaries to let some air in big fail. So I have gone back to the exact settings I had last night except dropping the timing 2 or so degrees. Ill just buy some 5 plugs and whack them in see what happens. So do you think the pics of my plugs look ok??? It has got a mildish cam best vacuum i can get hot is 10hg.

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    Let me guess, a Holley carb [ or clone ]?

    Agree, you should use NGK -5 plugs.

    Couple of other issues. Is the PCV hooked up? If so, it is probably not working with that low vac. Disconnect & plug for now. Also, you need MORE initial timing, not less, if you have 10" of vacuum. Increase initial timing to 35*. Yes, 35*!!! Idle rpm will likely increase 100-300 rpm, allowing the idle speed screws to be properly set. Report back with results & a permanent fix. Idle rpm increases because the engine is making more hp from extra timing.

  6. #6
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    35 degrees inital wtf. I dont think so my total timing isnt even 35 degrees. The PCV is hooked up is there any point in blocking it all off? Yes its a holley 670cfm street avenger carb.

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    You see, you are not understanding the relationship. The above test will take 5 min, & you will learn something....

    I run 48* of initial timing with my engine. Yes, 48*!! It is done with initial + vac adv added via manifold vacuum.

    An engine I tune for drag racing needed 53* at idle with the big cam it had in it. Probably would have stalled with less than 20*.....

    David Vizard. Author of 30+ automotive books, uni lecturer on motorsports, consultant to car companies, F1 teams etc, says this in his Holley carb book:

    " The optimum idle advance for a short cammed street engine is typically 35-40* & [ though not typically realised ] as much as 50* for a street/strip engine."
    Think about why timing at idle is mentioned in a carb book....

    Also, below, scroll down to post #6,

    http://www.hotrodders.com/forum/vacu...bad-47495.html

  8. #8
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    Mate, what is the engine combo again? I'm sure you've mentioned it in one of your other carb threads but please remind us.

    Quote Originally Posted by GtoGeoff View Post
    You see, you are not understanding the relationship. The above test will take 5 min, & you will learn something....

    I run 48* of initial timing with my engine. Yes, 48*!! It is done with initial + vac adv added via manifold vacuum.

    An engine I tune for drag racing needed 53* at idle with the big cam it had in it. Probably would have stalled with less than 20*.....

    David Vizard. Author of 30+ automotive books, uni lecturer on motorsports, consultant to car companies, F1 teams etc, says this in his Holley carb book:

    " The optimum idle advance for a short cammed street engine is typically 35-40* & [ though not typically realised ] as much as 50* for a street/strip engine."
    Think about why timing at idle is mentioned in a carb book....

    Also, below, scroll down to post #6,

    http://www.hotrodders.com/forum/vacu...bad-47495.html
    Can't argue with Vizard the Wizard but you do have to keep in mind he is talking about a small block Chev most likely and the Holden isn't quiet the same.

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    Quote Originally Posted by immortality View Post
    Mate, what is the engine combo again? I'm sure you've mentioned it in one of your other carb threads but please remind us.



    Can't argue with Vizard the Wizard but you do have to keep in mind he is talking about a small block Chev most likely and the Holden isn't quiet the same.

    308 holden
    single plane hi rise torque power manifold
    670cfm street avenger carb
    Cam Unknow??? Does have a bit of lope
    Hq Pre pollution heads
    Seems to be low compression highest reading some 155psi some 115psi lowest reading some inbetween around 130
    Genie extractors
    m21 4speed
    4.11 diff ratio

    Seems to idle ok at around 15 to 18 degree initital and drives pretty good as well no real flat spots accelerates good secondaries come on ok cant hear it pinging at all
    I just think my idle is rich and I cant for the life of me work out why I need the curb idle wound in so damn far.

    *** the only other thing I havent tried is winding the damn idle mixture screws out a couple of turns? Would this perhaps allow me to wind back out my curb idle??? I get the best vacuum though when they are only cracked open a half turn. Doesnt blow any smoke but smells a tad fuelly at idle

  10. #10
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    Quote Originally Posted by bfhoon View Post
    308 holden
    single plane hi rise torque power manifold
    670cfm street avenger carb
    Cam Unknow??? Does have a bit of lope
    Hq Pre pollution heads
    Seems to be low compression highest reading some 155psi some 115psi lowest reading some inbetween around 130
    Genie extractors
    m21 4speed
    4.11 diff ratio

    Seems to idle ok at around 15 to 18 degree initital and drives pretty good as well no real flat spots accelerates good secondaries come on ok cant hear it pinging at all
    I just think my idle is rich and I cant for the life of me work out why I need the curb idle wound in so damn far.

    *** the only other thing I havent tried is winding the damn idle mixture screws out a couple of turns? Would this perhaps allow me to wind back out my curb idle??? I get the best vacuum though when they are only cracked open a half turn. Doesnt blow any smoke but smells a tad fuelly at idle
    155 to 115?? thats way to much difference you have a ring/gasket problem with 40psi difference between highiest and lowest bore, thats why you fouling plugs

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    Quote Originally Posted by alffie View Post
    155 to 115?? thats way to much difference you have a ring/gasket problem with 40psi difference between highiest and lowest bore, thats why you fouling plugs
    Cylinder

    1 145 psi
    2 125 psi
    3 150psi
    4 125 psi
    5 115 psi
    6 120 psi
    7 115 psi
    8 125 psi

    I dont know though im a bit sus on the reliability of the guage and the 150 psi and 145 psi but maybe its dead accurate. All the plugs though seem to foul all the same wouldnt the 150 psi and 145 psi bore spark plugs show improvements. They all seem pretty much the same

  12. #12
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    Quote Originally Posted by bfhoon View Post
    Cylinder

    1 145 psi
    2 125 psi
    3 150psi
    4 125 psi
    5 115 psi
    6 120 psi
    7 115 psi
    8 125 psi

    I dont know though im a bit sus on the reliability of the guage and the 150 psi and 145 psi but maybe its dead accurate. All the plugs though seem to foul all the same wouldnt the 150 psi and 145 psi bore spark plugs show improvements. They all seem pretty much the same
    drop some oil in the low ones ans see if they improve

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    Immortality,

    No Vizard was NOT talking about SBC [ post #8 ]. This was in his Holley carb book. And the idle timing #s I quoted, 48* & 53*, were NOT Chev engines....

    It makes no difference whether it is a Chev, Holden or Goggomobile engine. The functions are the same, all that will differ will be the actual timing #s [ slightly ] between engines.


    To the OP:

    Try this 5 min test. Warm up the engine, & with engine still running, loosen dist clamp & turn dist slowly to advance timing. Keep advancing until idle rpm is at a maximum. Now check timing. Do not be surprised if timing is between 30-50*.

  14. #14
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    Ok so i had my distributor set around 15 to 18 degree timing initial I actually changed the vacuum advance from ported which was on the metering block of the carby to full vacuum advance which is on the base of the carby. The car is a manual not auto. Anyway I started it cold checked timing and it was around the 15 to 18 degree initial timing as it warmed up and got to full operating temp the initial timing is probably more like 28 or so degrees now. The idle didnt change I expected it to increse but still the same so i didnt make any adjustments to curb idle. I did notice though the manifold vacuum on the guage was a lot more steady between 10-11hg it seemed to idle great. Still a bit fuelly at idle havent taken it for a spin yet probably tomorrow but what could I excpect pretty sure my distributor doesnt go past 32 degrees total. Only thing I can think of now is drilling holes in the throttle butterflies dont really want to do this or make idle fuel restriction mods. Idling around 900rpm but still way to much screwed in on the curb idle I think

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    Quote Originally Posted by GtoGeoff View Post
    Immortality,

    No Vizard was NOT talking about SBC [ post #8 ]. This was in his Holley carb book. And the idle timing #s I quoted, 48* & 53*, were NOT Chev engines....

    It makes no difference whether it is a Chev, Holden or Goggomobile engine. The functions are the same, all that will differ will be the actual timing #s [ slightly ] between engines.


    To the OP:

    Try this 5 min test. Warm up the engine, & with engine still running, loosen dist clamp & turn dist slowly to advance timing. Keep advancing until idle rpm is at a maximum. Now check timing. Do not be surprised if timing is between 30-50*.
    Well I guess chamber design/efficiency makes no difference then? All though admittedly I was thinking about VN heads, I forgot he had the early style HQ heads.

    I like EFI with a fully programmable ignition curves, and yes I like to add idle timing over stock.

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