Chrysler 331 Hemi - Affordable Excellence: Part II

Spark-Plug Tubes
There were three different spark-plug tubes used in Hemis and they can be found in steel or aluminum. The '51-53 steel tubes are 6 13/32 inches; the steel and aluminum tubes for '54-55 are 5 29/32 inches, and the '57-58 aluminum tubes are 6 1/8 inches. These tubes were considered consumable items and were to be used without spark-plug washers.

With stock valve covers, the spark-plug wire covers should always be used, as they served three functions: They hid the wires, kept water out of the tubes, and pushed down on the metal rings to help seal the rubber gaskets to the rocker covers to prevent oil leaks.

On this engine, we're going with Hot Heads aluminum rocker covers that use seals that fit into the spark-plug holes.

Gaskets
You probably won't find gaskets for Hemis, or most other vintage engines, at your local parts house. Our complete set, including a modern lip seal for the rear main cap, came from Best Gasket.

Fly Wheel
Chrysler must have had an engineer who spent all day long figuring out how to do things differently than everyone else. To that end, the Hemi crankshaft flanges were not tapped for capscrews, rather bolts were used. But not just any bolts, Chrysler bolts have special heads that fit into a recess cut in the flywheel. We used a steel truck flywheel that accepts an 11-inch clutch.

Starter
Hemis will be found with either six- or 12-volt starters, and they will interchange. However, the number of teeth on the ring gear will complicate things when swapping-the tooth count was 146 from 1951-56 (actually all the way back to 1933), but it was 172 for 1957 and 1958. Chrysler changed to 12-volts in 1956, and that year had a unique starter, as it's the only 12-volt starter that is compatible with a 146-tooth ring gear. At one time, that one-year starter was the only one to retrofit a six-volt engine with a 12-volt starter. However, that has changed thanks to Powermaster, which makes high-torque gear reduction starters for both diameter flywheels.

Headers
Hemi heads have either round or rectangular ports; however, the Doug's headers we used will fit either. Available either painted or coated, we chose these tight tuck-design headers for their extra-thick flanges and large tube size.

Wrapping Up
While we weren't able to dyno test this engine, similar combinations have produced from 375 to 425 hp. But, we weren't really concerned with the numbers for bragging rights, as John Beck said, "It is what it is." Our goal for this engine was to build an affordable Hemi that was reliable, would run on regular gas, and produce respectable horsepower and torque, and we're confident it will meet all our requirements.