Hot rodding the HEI distributor
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Number 1 plug wire should be at the front of the distributor just to the driver’s side of centerline. The vacuum advance can should be pointing roughly at the passenger side front tire. If that's not your #1 plug wire, or your vacuum can is pointed in a weird direction then you have the distributor installed off by a few teeth. It won't hurt performance if timing is still set correctly but plug wire routing gets a bit messy. | Number 1 plug wire should be at the front of the distributor just to the driver’s side of centerline. The vacuum advance can should be pointing roughly at the passenger side front tire. If that's not your #1 plug wire, or your vacuum can is pointed in a weird direction then you have the distributor installed off by a few teeth. It won't hurt performance if timing is still set correctly but plug wire routing gets a bit messy. | ||
| − | The vacuum advance can should be plugged into a | + | The vacuum advance can should be plugged into a full manifold vacuum source on the carb. This is a vacuum port on the carb that provides FULL vacuum at curb idle. Using this vacuum source will allow you to close your throttle plates a little and maintain the same idele speed. This does two things. First, it will deter engine run-on, or, dieseling. Also, you will find that the engine is cooler running around town in traffic and has much better throttle response. It will have no ill effects at WOT because there will be no vacuum at WOT so you will be running exclusively on mechanical advance. Full manifold vacuum is by far the best way to connect your vac. can. As always, disconnect and plug this line when setting initial advance. Plug it back in when the initial has been set. Finally, adjust for proper idle speed. |
WATCH YOUR IDLE RPMS WHILE YOU SET INITIAL ADVANCE TIMING!!! You note that the centrifugal advance curve that I recommended above starts at about 800 RPMs. If you try to set your initial timing with the engine idling ABOVE this RPM point you will NEVER get a true initial advance reading since the centrifugal with be partially advanced at that point! Set it with the idle temporarily slowed WAY down if you have to but DO IT RIGHT! | WATCH YOUR IDLE RPMS WHILE YOU SET INITIAL ADVANCE TIMING!!! You note that the centrifugal advance curve that I recommended above starts at about 800 RPMs. If you try to set your initial timing with the engine idling ABOVE this RPM point you will NEVER get a true initial advance reading since the centrifugal with be partially advanced at that point! Set it with the idle temporarily slowed WAY down if you have to but DO IT RIGHT! | ||
A final word about that HEI "module:" Lotsa mystery around this little "thingamajig." This is just the little electronic brain located on the floor of the distributor housing with 4 wires going into it (2 per side). All it does is read the magnetic pickup signal from the magnetic pickup assy. around the distributor shaft and then using this reference signal, tell the coil when to fire and with how much "dwell". I always recommend a good stock GM module, not a parts-store cheapie. No reason to go crazy and get one of those $70 “super-high output modules here”- I have tried them and they do nothing for performance. But get a genuine GM one. Stock GM modules incorporate what they call a "variable dwell" circuit that reduces dwell at lower RPMs to keep the coil from over-saturating. This is good for sharp performance and long coil life. Some parts-store modules don't have this circuitry in them. | A final word about that HEI "module:" Lotsa mystery around this little "thingamajig." This is just the little electronic brain located on the floor of the distributor housing with 4 wires going into it (2 per side). All it does is read the magnetic pickup signal from the magnetic pickup assy. around the distributor shaft and then using this reference signal, tell the coil when to fire and with how much "dwell". I always recommend a good stock GM module, not a parts-store cheapie. No reason to go crazy and get one of those $70 “super-high output modules here”- I have tried them and they do nothing for performance. But get a genuine GM one. Stock GM modules incorporate what they call a "variable dwell" circuit that reduces dwell at lower RPMs to keep the coil from over-saturating. This is good for sharp performance and long coil life. Some parts-store modules don't have this circuitry in them. | ||
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