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Part 5: Hemi Ignition Upgrades
The early hemis had a lot of high grade features in their day -- like high nickel iron castings, forged cranks and hardened exhaust valve seat inserts. The ignition system was one of those premium items. The distributor was a dual point Autolite from the factory. Although top-of-the-line in its day, it is pretty archaic by today's standards. Fortunately, Chrysler didn't change very much about distributor design over the years, except upgrading to electronic from points triggering. Thus, it doesn't take very much to adapt a modern aluminum electronic distributor to a 331 or 354 hemi. The distributor from a 318, 340, 360 series A-LA engine drops right into one of these engines. The only modification needed is to weld a 1/4" long extension to the drive tab on the end of the shaft so it will engage the cam driven distributor/oil pump gear, as shown in the picture below.


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The distributor will also fit in the bigger 392 hemi but the extension tab needs to be 5/8", which is a little too long. The only good option there is to make a new, longer distributor shaft. You can get one of these distributors at your Pick-A-Part for probably around $10 and as long as the shaft is tight and there is no bearing wobble, it is as good as the $$$ aftermarket ones. Your local parts store carries adjustable vacuum pots for it and Jeg's or Summit sells spring and weight kits.

The next really good thing I did was add a MSD 5 ignition box to the system, as shown in the picture below. Not as sexy as the MSD 6, it costs less than half as much and they claim the '5' is good for speeds up to 6,000 rpm, while the '6' goes to 8,000 rpm. Since I can cruise at 60 mph @ 2,200 engine rpm in fourth and my speedometer only goes to 120 mph, I feel that the 170 mph @ 6,000 rpm capability is adequate for my street rod around town. It may give me problems keeping up with traffic on I-5 heading to 'Frisco or LA.


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Accel 8.8mm universal plug wires have an extended tip on them that perfectly replaces the long porcelain insulators that came on the engine as original equipment, as shown in the picture below. Just be sure to use silicone grease or they stick tight to the plugs.


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I also found that Toyota "hemi" valve cover hole covers make great ones for the Chrysler. The picture below shows a close-up of the ones I use that have an "R" cast into them. There is another version I have found without the R that are flimsy and always cracked. This picture also shows a rubber ring on the bottom side that needs to be trimmed off.


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The next picture shows how the valve covers came from the factory.


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Those long skinny pans hide the wires and press down on steel washers, that in turn press down on rubber grommets that seal the spark plug tubes, as shown in the pictures below.

  
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The next picture shows what happens when those pans are left off. The spark plug tubes have nearly straight tops and without the steel washers, the rubber grommets aren't held in place and oil leaks badly.


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The next picture shows a jig I made from a piece of oak. I drilled the proper sized hole to fit snugly on the tubes. Then I slit the wood and installed two thumb screws so it could be made to clamp the tubes tightly. I put a tube into the jig with about 1/8" sticking out and very carefully tapped the edge over with a ball-peen hammer to make a flange. I only had a couple of very tiny splits in the flanges out of the 8 I modified that I brazed and filed smooth. Now the tubes firmly compress the rubber grommets when the sparkplugs are installed and leaks are a thing of the past.


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Here are all the parts of the spark plug tube -- the Toyota hole plugs, the Accel plug boot and the wide flange tube.


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Click here for Part 6: Hood Blower (Fresh Air) Scoop


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