Perplexed

[jspell]

I've been struggling with a problem for a month need some help...Engine came off the dyno running great idling great.  Put it in the dragster engine won't idle clean.  Three differences: the dyno has a 7AL-2 ignition setup, collector style headers, and a different fuel system.  Engine is a 15 to 1 SBC with HFE intake and a dominator.  The dragster has a new Mallory HyFire 7C ignition and zoomie headers.  I'm starting to question whether zoomie headers may be a problem on a carbureted gas application?  or maybe the new ignition has an issue?  any thoughts???

[dreracecar]

Zoomies should not be the. cause a problem. How good is the battery?? Is the fuel pump taking away power needed to run the ignition system? Anytime one runs any style standard ign system (not magneto) with a box (msd,hy-fire. etc) you need to run an altenator to keep the volts up

[Paul New]

Zoomies should not be the. cause a problem. How good is the battery?? Is the fuel pump taking away power needed to run the ignition system? Anytime one runs any style standard ign system (not magneto) with a box (msd,hy-fire. etc) you need to run an altenator to keep the volts up

Ditto!

[Totally T]

Im with Bruce...Check the Voltage to the ignition and make sure the pump is functioning like it should. If you suspect voltage to be a issue, stick the charger on it and try it to see what happens.

I do not know alot about the Mallory but I do know it has a start retard on the timing and it also has 3 timing retards on it as well....need to put a timing light on the engine once running to see what its doing for timing.

[GlennLever]

Check grounds.

People go so far as to run separate grounds to the heads for the spark plugs.

If the chassis is powder coated make sure the powder (or paint) has been removed at your ground points.

[jspell]

Thanks Guys, all great ideas.  I'm back at it this weekend...will keep you posted.

[coupemerc]

I'm assuming that you have all new fabricated fuel lines. Make sure that they are all cleaned out and that there is no debris sticking the needles open on that dominator. I'd put some good fuel filters in it and run it for a while. Then take the filters away when you run the car. Good luck.

[masracingtd1167]

Hi John  When you dynoed did you use the same carb or just a different pump and regulator ? It could be as simple as some dirt in the air bleeds . Some of the new race fuels leave a residue in the carb so it would be a good idea to check that . Chuck has a good point about the new fuel lines . How about float levels . fuel pressure 6 to 7 lbs . Dose your fuel pump have a by pass back to the tank ? Make sure that it is not stuck open . Are you running a crank trigger ? If so make sure your rotor is fazed correctly . The only other thing I can think of is your pick up wires . Make sure they are not backwards . Thats all I can think of . I would bet it is something very simple . Keep us posted !   

[PSweeney]

what is it timed at ?  and when will it not idle, ie in neutral or in gear.  If it stalls when dropped into gear, bump the initial timing 2 degrees but ensure you still retain correct total timing.

[jspell]

It likes 34 degrees, it does have the 20 degrees start retard, I'm going to disable that function and try it. It's supposed to go away at >500RPM. Mallory says certain radical cam profiles affect the start retard function.  Will check trigger wiring too.

[masracingtd1167]

Is the distributor locked out ? I don't think you need the start retard .

[PSweeney]

It likes 34 degrees, it does have the 20 degrees start retard, I'm going to disable that function and try it. It's supposed to go away at >500RPM. Mallory says certain radical cam profiles affect the start retard function.  Will check trigger wiring too.

it's likely it needs more timing at idle due to the difference in loads placed on it by the dyno and the convertor/trans when fitted in the car.  Lock out the total timing at 34 degrees, will clean up the idle and it won't build heat so quickly.

[jspell]

I'm going to disable the start retard tomorrow and hopefully that cleans up the idle. timing is locked at 34 deg.  I'm going to check the crank trigger pickup polarity also, I believe that can cause havoc.