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So between all the dyno testing and life, I have a 1970 Rallye 350 with a LOT of stuff done to it. One thing I've done is put a Sniper on it (the engine is a 455). As Holley recommends I initially ran the engine controlling just fuel. Actually got about 15 miles on the car, after owning it for about 8 years. Yesterday I added the spark control to the Sniper set up. I had a Petronix distributor. All I have to do is lock it out. Guess what? There aren't provisions to lock it out like an MSD distributor. But I have a drill press and enough skills I drilled a hole to "drop" the pin in to lock out the mechanical advance. No problem. Then I removed the vacuum advance "canister". Well, there was no way to prevent the "breaker plate" (I don't know what it's called on a non points distributor) from spinning without the vacuum advance holding it from moving. I drilled a few holes and put some machine screws in it to prevent it from spinning.
I now set everythign up and started it up. When the engine idle downs it stalls randomly. The RPM signal drops to zero when the engine is still running. This tells me the air gap from the reluctor wheel to the pickup coil is to tight. I moved my set screws up and down to change the angle of the pick up coil and it seems to be fine, no more stalling, but below 900 RPM the RPM signal spikes (the engine speed is NOT changing). So the reluctor wheel and pickup coil are probalby not in the same vertical plane, so at low RPM it's picking up the front and back as two diferent signals. I ordered a MSD ProBillet to make this easier.
Bottom line, don't try to lock out a Petronix distributor.
Why wouldn’t you have just ordered a Hyperspark dist? They're plug n play, and I believe they now make a ready to run one now as well.
Mainly because the evil I know is better than the evil I don’t know. We have made over 900 Dyno pulls with a MSD ProBillet and I know it will do exactly what I need.
Mainly because the evil I know is better than the evil I don’t know. We have made over 900 Dyno pulls with a MSD ProBillet and I know it will do exactly what I need.
I understand. But I’ve used a bunch of the Hypersparks with zero failures so far. Just an fyi.
Last edited by cutlassefi; May 26, 2026 at 05:58 AM.
I understand. But I’ve used a bunch of the Hyoersparks with zero failures so far. Just an fyi.
So I clearly should have bought bought the Hyperspark. After futher research that's a Hall Effect sensor, which just has a square wave out, same amplitude just changes frequency with RPM. The mag pickups change both frequency and amplitude with RPM. I still have some EMI issues, although not as bad. I am intimately familiar with how hall effect and mag pickup sensors work, and I also know hall effects have very little EMI. Just had my head up my ***. Summit claims all the Petronix distributors are hall effect, but that's fake news, they are all two wire sensors so they have to be mag pickups. For some reason the Holley Dual Sync is on sale at Summit for a pretty good deal, $300ish which is about $225 off. So I may pick up one of those as I suspect I'll eventually go port injected and need both sensors. It's only money, I can't take it with me! I'm sure I can sell my ProBillet at Homecoming/Nationals swap meet with all kinds of other left over parts (like the Batten heads.....)
I did a motor for a guy who had a pertronix dizzy and a carb set up. He went FITech and locked out his original pertronix no problem. They have a vac advance lockout plate and a plug for the mechanical advance lockout. The billet flame-thrower dizzys come with the mechanical lockout plug. He had to buy the vac advance lockout plate
been running for years now.
Last edited by CANADIANOLDS; Feb 1, 2026 at 08:58 PM.
To finish this topic....The MSD ProBillet still had the same problems as the Petronix distributor. Once I added spark control to the Sniper the car would sit there and idle and just stall at times. When I video tapped the Sniper display screen with my phone you could see all the data go red for a split second, meaning it lost the CAN communication, and the engine would stall. I concluded this was EMI (electro magnetic interference) caused from the mag pick up. It did NOT do this when the Sniper was controlling only fuel. The first thing I did was to buy some braided sleeving and cover all the wires and ground each end. No improvement, still stalls randomly, worse when it's wamer (meaning having idled longer).
Yesterday I put the dual sync distributor in, which is a hall effect sensor and NOT mag pick up. Car idled for about an hour and never stalled. It would have stalled over a dozen times if I did this with the mag pickup, probably several dozen.
Moral of the story, listen to Mark and put a Hyperspark or something like that and NOT a distributor with a mag pickup if you are going to use a Sniper. Now, I know people that have used mag pick ups on Snipers and never had issues. So there has to be another variable that makes my car so much worse. But go to a hall effect, much better.
Good to know that you solved the problem with a hall effect distributor. Grounding and bonding properly is quite a task, especially if you're running a modern electronic system like the Holley Sniper.
