View Full Version : ZZ-502
07-23-2003, 01:07 PM
I am running a GM Performance ZZ-502 in a 2500lb bracket drag car. Currently the car runs in the 10.40s @ 125 with peak RPM @ 6500. My goal is to get the car to run 9.90s while leaving the motor as stock as possible.
Currently there is a problem where it tends to misfire at RPMs above 6000. Although I am not certain this is an ignition problem I suspect the ZZ-502 HEI ignition system is not suitable for the higher RPMs. GM advertises 5800 max recommended RPM for this motor.
What does MSD offer in HEI modifications or other products that are suitable for this application up to 7000 RPM?
Thanks in advance.
07-23-2003, 03:06 PM
Normally the stock ignition is good to about 5 to 6000 RPMs; I would recommend using an MSD 6AL, which will provide a strong voltage and current output. This unit is capable of up to 14,000 w/ 14.3 volts supplied. So if your factory ignition is falling short this will sure help.
07-24-2003, 02:06 PM
I have just ordered the Digital 6. I like the two step adjustable rev limiters built in as well as the lower power requirements since I am not running an altenator.
How about running the stock HEI coil with the digital 6? Any concerns?
07-24-2003, 02:20 PM
No concerns to worry about, it will work fine.
07-24-2003, 03:02 PM
Any spark plug suggestions for this same setup? Currently running delco R4 gapped at .035. They have a bright finish with a pointed tip.
07-25-2003, 10:28 AM
No special plug required, just a standard plug will work fine, you may want to increase the gap to .045 for a better fuel burn.
07-29-2003, 07:07 AM
Can the Digital 6 adjustable retard be used in a "continuous duty" rather than only in "momentary" situations like nitrous/top end? I would like to use it to adjust timing rather than turning the distributor. Of course this would require constant +12v on the pink wire.
I intend to run different grades of fuel on ocassion and would like to compensate timing accordingly. Also, I prefer using the digital switches over twisting a knob for better control when making adjustments.
Since the Digital 6 manual does not state one way or the other, I called and spoke to one of the MSD techs yesterday. He recommended not doing this. Instead he suggested using the 8680? product. He offered no explanation.
What is the reason(s) I should not use the the Digital 6 adj top end retard for this purpose?
Thanks in advance.
07-29-2003, 08:27 AM
There is no reason why you should not be able to hook the pink wire to a wire that has 12 volts when the key is in the run position. This would allow you to run retarded timing as long as the ignition key is in the run position. I am note sure why the tech said you cannot run 12 volts to it. He may have thought that you where going to put constant 12 volts on it at all times. The Pink wire will only draw about 20-25 milliamps.
07-29-2003, 10:11 AM
I dont think he was as concerned about the wiring as the suitabilty of the application. The only disadvantage I can think of is the single stage retard only operates above 2000 rpm.
I will give it a try unless you have any concerns.
Thanks for your quick response.
07-29-2003, 01:47 PM
If it was to be activated at all times, then it is basically considered as an RPM activated retard at 2000 RPM's, but no harm will be caused to the unit.
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