I’m experiencing ignition timing retard when rpm increases with this Pertronix Digital HP ignition in my 383 sbc. Parts: MSD 85501 locked distributor, Pertronix Digital HP and matched Pertronix coil, Cloyes Hex Adjust timing cover, mild solid roller cam. The cam isn’t walking forward. I can set 34 degrees at 1000 rpm, take it to 4,000 - 5,000 rpm and timing has retarded 10 degrees! The ignition retards smoothly and is inversely proportional to rpm increase. I tried several timing lights. I currently have 44 degrees of timing at idle, knowing it is 34ish at 5k. Starting is ok with the start retard feature of the ignition box. Do I unknowingly have the latest “hot setup”? What should I do here?
Tech at Pertronix was cooperative but said they’d never had a customer experience this. He forwarded the issue to engineering and said he’d reply back to me, but no word yet (several months ago). The mode selector was returned to zero after programming the unit and setup of the Digital HP was accomplished three times after noticing the problem. The problem arose on the engine stand and since installing in the truck, I’ve been delayed in running the motor.
Electronic component latency timing seems to effect some timing boxes more than others. Once the cooling system is complete and motor running I’ll check total timing retard at a probably scary high rpm and adjust from there. This is a footbrake car and advance at 2500rpm being 45 degrees might even help throttle response. This 45 degrees will retard to 35ish degrees by 6k and might be ok. Check your timing for retard, especially those with what they think is locked timing.
Update: I have checked cam walk with the Cloyes quick-button timing cover and was able to remove all but 7 degrees of timing retard. There is definitely a bit of preload timing cover tension now, but I still have timing going from 41 to 34 degrees in a smooth, linear manner from idle to 6,000rpm. It is what it is. Could a worn timing chain contribute to this?
You should not set total timing at idle,ever, unless it is a stock bag-o-crap. 4000-5000 minimum,depending of course what your max rpm making power is. At higher rpm all the slack in the chain, oil pump load, cam walk, twist in the cam is done.and do not preload those little cam buttons, you should still have .005-.007 If you have centrifugal advance then set your initial, then rev it up to set total. Anything else you are just wasting time and power.
Posts: 863 | Location: ft laud | Registered: September 02, 2004
@The distributor is locked out and I still have 6 to 7 degrees of retard. I want to set timing at 34 degrees, but have to set at 41 degrees because as rpm rises, the timing creeps back to 34 at 4500rpm and stays there as rpm climbs higher. There is currently a slight amount of preload on the cam button. Cloyes instructions have the installer bottom the button against the cam and lock it there.
Mike - Yes, that is the cover I use.This message has been edited. Last edited by: Mike Allred,