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ok about 4k and after my engine seems to stutter somewhat , is this caused by not getting enough fuel? im three turns out on my SU;s but i have a decent amount of mods, i set the timing with a vaccum gauge to about 14 on the balance tube. valves recently adjusted hot to .010/.012 any help gettin this thing dialed in would be appreciated. my mods are as follows


P&P head,stage 2 cam,bored .060 over, lightened flywheel,ported intake manifolds, polished Z therapy carbs, Top end performance longtube 6 into 1 header, Pertronix ignitor system with flamethrower coil. way..

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Hmm not sure about Petronix ignitors I know they replace the points but does the distributor still require the little capacitor on the side? If so that could be playing games, you have ugraded coil so i'd rule that out for now.

Does it play up hot or cold?

Sounds to me like carbs are out of adjustment , could be a blockage, how about your fuel filter when did you last change that?

They are rebuild carbs from Z therapy right? so shouldn't have vacumm leaks, check the intake manifold for split hoses or loose connections.

How about your spark plugs they could have fouled up from the carbs being too rich. If they are all black give them a clean with a wire brush and rinse them in kerosine or something similar.

You could also check spark leads for resistance with a multimeter but remember longer wire means more resistance what you'd be looking for is very very high resistance.

Good luck.

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  • 3 weeks later...

How do your plugs look . I also start stutering at 4k but just got my

stock engine with headers running after setting 18 yrs. My carbs

were cleaned and are set at about under 1 turn. I do have some valve tap so going to readjust the valves. Then see if I can run the carbs a little richer. some of my plugs are clean #1 and #2 look good

#3 has more carbon #4 is clean but wet. #5 and #6 are fine. Maybe try to run yours a little leaner.

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I had the same problem. I got that great ZTherapy video (Thanks Pam!) and I did to my SU's what I could do. I even made one set of needles slimmer to get more fuel in the middle range. Looking at the plugs I got a good mixture with only 2 turns out (Needle shaft downwards 1,5 mm). It became much better, but not totally. I than advanced the Ignition from 17 to 20 BTC and it became much better. The problem is now only when I accelerate under load (uphill). I will try 23 degrees the next time, using a 98 octane fuel. I think the ignition is the key when everything else is okay.

Good luck


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