BluePrint Engine HEI Distributor

[Ernest]

Im thinking about trying one out to see how good they are since they are used on their crate engines.

Advertised with a melonized gear, which is a plus for us roller cam guys, typical amazon/ebay distributors use iron type, more for flat tappet... has anyone ever used one for their own engines?

GM SB and BB Compatible HEI Ready to Run Distributor - 65K Volt Coil - Black Cap

Description: BluePrint HEI Distributors LARGE cap design. Confirm Firewall, and wiper motor clearance before ordering. Features and Benefits: Computer-Controlled Compatible: No Trigger Style: Magnetic Advance Type: Vacuum and mechanical Cap Style: Male/HEI Mechanical Tach Drive: No Slip Collar...

blueprintengines.com

 

[Bonnewagon]

That sounds like a good deal if you can't find a stock distributor to rebuild.

I have always used a stock HEI since they first came out in 1975. But I do tighten up the shaft play with dedicated hardened distributor shims. You take off the gear and shim the shaft to get .010" clearance. Then you grease the shaft with high temp grease. I found stock modules, pickups, and coils to be very reliable and long lasting. Just be sure to add the heat sink grease under the module. Special gears are available for various uses.

Junk yards used to be full of HEIs but are probably best found at swap meets now. Once rebuilt, I find they last forever on a seldom driven vehicle.

 

[Ernest]

Given the quality and reliabilty that BluePrint engines are known for, this distributor hopefully should be no different.

For the price point, its an excellent deal compared to a junkyard unit that people will probably sink more money rebuilding it.

From what i've read, the consensus is, .020 is the tightest you want to go, my HEI progression ignition distributor came set exactly the same.

The non original distributor that was installed in my ZZ4 engine was set around .040 or so from what i remember, whatever brand it is, it just says GM08 279 engraved on the shaft collar.

After doing a little research, its looks to be either from WAI or Spectra Premium, it ran really smooth though, started the engine within a revolution of cranking with little to no wear pattern on the gear teeth, now set to .020 gap, i did remove the adjustable vacuum advance can and replaced it with a 10degree vacuum advance can so i could run it straight off manifold vacuum for a 15degree total timing at idle.

 

[Bonnewagon]

From what I read, the gear/housing gap translates into timing change due to the rotation. .005" was the absolute tightest allowable due to thermal expansion. .010" was the best compromise. The timing changes more as the gap gets bigger. I have come across used distributors that had gaps up to .100". Imagine the timing change from that.

 

[Ernest]

The timing changes more as the gap gets bigger

Would you happen to know, as the gap get wider, does the timing advance or retard?

The reason i ask, and it might be just in my head, but i remember when i first got the malibu, the ZZ4 had a Holley 770SA carburetor and the WAI/Spectra Premium distributor, both completely untouched at the time, with the fuel bowls full, by hand, i throttled the carburetor manually just half way to set the auto choke and for a quick shot of fuel into the intake, with a turn of the key, with less than a full crank, the engine roared to life almost instantly, and that was from a cold start. But after i rebuilt the distributor with a GM module, GM pickup, a Standard Motor Parts Blue Streak ignition coil, a NOS ZZ4 distributor shaft with its original weights and springs, and set the gear to .020 gap, the engine turned over 2-3 turns before it fired right up, so i put the distributor back the way it was originally, back to the same 2-3 turn overs before it started. Go Figure

BTW... my progression ignition HEI distributor does the same 2-3 turn overs before the engine fires right up after seting the auto chock and on a cold start, and thats right out of the box.

 

[Bonnewagon]

Would you happen to know, as the gap get wider, does the timing advance or retard?

This is taken from a Car Craft/Motor Trend article:
" Mr Gasket sells an inexpensive distributor shim kit that you can use to reduce the overall endplay down to around 0.015 inch. Most stock HEI's have as much as 0.060 inch or more endplay. The excess clearance allows the drive gear to climb the cam gear and retard the ignition timing. Reducing the endplay eliminates this problem."