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Recollections of a Ramcharger, #9: Developing the Hemi

The development of the 426 Hemi is well documented in the book Chrysler Engines 1922–1998 by Willem “Bill” Weertman, also published by the Society of Automotive Engineers. Bill was the assistant chief engineer of Engine Design.

A990 engine

The first design layout is dated March 28, 1963, which predated formal approval of the program by several weeks. The first engine, EX-1, was assembled in the Motor Room in late November and mounted to the dynamometer on December 5, 1963. It was installed in Room 15 and mounted to an electric dynamometer. Arnold Hayden was the operator, and throughout the day of the 6th the engine was motored to check oiling and valve-gear operation.

An electric dyno is capable of being run as a motor to turn the engine up to the rated speed of the dyno and as a generator for power absorption. The power from the generator is fed to a resistor bank on the roof.

The dyno in Room 15 was rated at 450 hp and 5,000 rpm. The dyno is restrained from rotation by a beam attached to a large scale that measures torque. Back then there were no electronics to record data, so engines were run at a constant speed until max power spark was set and all measurements stabilized. The measurements were then written down by hand. This was a very slow process.

Exhaust gases from each cylinder were piped into a console that bubbled the gas up through water and gave an air/fuel ratio. A power run required up to one-half, and hearing a Hemi at 7,200 for 10 minutes is a real trip.

At that time I was a Performance Development Engineer, and along with early Ramcharger Bob Mullen, was responsible for race engine performance. Ramcharger Steve Baker was responsible for engine build and durability. We reported to Bob Lechner, who had been in charge of race engine development from the beginning of the wedge [V-8 engines with wedge heads, created after the original Hemi and Poly V-8s].

426 Hemi with Mike Buckel and Forrest PitcockI was on duty when EX-1 was first fired late in the day of December 6. Ev Moller, manager of the Engine Laboratory, came down and took charge of the first run. The engine had the two-plane single 4-barrel intake with a Holley carburetor with jets that Ramcharger Gary Condon had guessed at. The exhaust was a set of headers coupled to flexible tubing and running into the vacuum trench under the floor of the dyno room.

The ignition and fuel were turned on at 2,400 rpm and the throttle opened. Data was taken at 400-rpm intervals. I had my trusty slide rule to calculate the output power from the scale reading and engine speed. The faster the engine ran, the more excited Ev became, and he ordered the test to continue to 5,600 rpm where the observed power was 530 hp. Everybody was ecstatic as we were seeing 50 hp more than the best wedge. However the dyno was out of service for over six months because the internal coils were shifted and burned.

EX-1 was then moved to Room 12, one of the race rooms, which had an 800-hp, 10,000-rpm, eddy-current-type dyno. This dyno just heats up water as it absorbs power and is not capable of motoring the engine. Forest Pitcock, future Golden Commando, was the operator. The race rooms had six-inch stove pipes ducted to the vacuum trench. Headers were installed backwards on the engine with the ends just into the stovepipes. The stovepipes were not reliable but provided a realistic exit for the headers. We spent a day or two sorting out the final 4-barrel carburetor jets and made over 550 hp at 6,000 rpm with no power drop at 6,400 rpm.

Within a couple of days EX-2 became available and was installed in the other race room, cell 13, with Ken Heatlie, the operator. In less than a week EX-1 suddenly lost oil pressure and was sent to the motor room for inspection. About the time that we figured out what happened to the EX-1 engine, EX-2 also lost oil pressure.

Both engines had developed a crack in the web between the main bearings and cam bearing. Analysis showed that the engines had not been properly annealed at the foundry. All told, we went through engines up to EX-10, also discovering that bores would split.

Bill Weertman went to the Indianapolis Foundry to manually shave cores making the bore walls thicker and supervising the block annealing process. The block that won Daytona was cast only ten days before the race. We ran one engine on a durability test lasting 3-1/2 hours non-stop from 6,400 to 6,600 rpm. Successful completion of that test gave all of us a high level of confidence in our new engine. Richard Petty won the Daytona 500 on February 23, 1964, and was followed by two other Hemi Plymouths.

Talk about the series in the Allpar Forums • Read other Ramcharger Recollections • Allpar racing page

1. Introduction: Joining the Ramchargers10. Drag Racing the Hemi19. The 1965 championships
2. 1961 Super Stock racing, experiments11. 1964 Hemi Domination 20. Puzzling results in ’66
3. Racing a Chevy on its home turf12. First Late-Model Hemi Dragster21. Rocket fuel, girdles, and springs
4. Trying Automatics13. Max Wedge Family Car22. Squirrely runs and a strong finish
5. 1962: Max Wedge, Indy Nats, Big Trucks14. Birth of the Funny Car23. Back in the engine lab...  
6. Al Eckstrand’s Last Ramchargers Race15. The Trip from Hell24. A revolutionary new body
7. Testing Tires and a New Rig 16. Clobbering Ford, “Funny Cars”25. Supercharging the big Hemi
8. Match Racing, Engine Lab, Jail17. Nitro ’6526. At the SAE presentation, 2012
9. The Hemi: Elephant Rising18. Big loads of nitro27. The 1967 racing season


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