The piston assembly was also...
The piston assembly was also weighed, this time to determine the weight of the rotating mass to balance the crank. The pistons were already organized into sets according to their relative weights at Egge when they were machined, but a good machine shop will bring them within at least a half gram, just like the rods.
Speed-O-Motive has been known as the stroker experts since 1946, so there was no doubt in my mind that it would be the perfect choice to handle the machining chores. Another name synonymous with vintage engines is Egge Machine Company, who supplied all the internals for the Hemi, save the camshaft, the crank, the rods, and the springs. Egge runs a first-class business that casts pistons for everything from, well, Flatheads to Hemis, and also stocks every internal part you can think of for vintage engines from 1900 to 1980. A camshaft was ordered up from legendary Mooneyes, ground by the master himself, Bill Jenks. With a spec sheet with that much history, I was sure to be in good hands.
This month, we're going to cover the machining portion of the Hemi build, with the assembly and a few other tips to follow in the coming months. Stay tuned, and help us keep the Fire Power lit!
Hemi rods are full floating,...
Hemi rods are full floating, so there is a bushing in the small end for the piston pin to ride in. New bushings are pressed into the small end of the rod and then honed to size to fit the piston pin. The big end is honed in the same matter, sans the bushings for the rod bearings.
When we disassembled our engine,...
When we disassembled our engine, we found a few of the rod bearings had spun on the crank, causing marring on the crank journals. The crank was sent out and ground 20/20, or 0.020-inch under on both the main and rod journals.
Weights were attached to the...
Weights were attached to the rod journals to mimic the weight of the rotating assembly, and the crank was balanced at 500 rpm.
A readout on the balancing...
A readout on the balancing machine told the operator where weight needed to be removed-as in the case of the hole drilled on the crank web-or needed to be added; see the welded area just below.
With hardened seats already...
With hardened seats already installed on the exhaust side of the head, it was possible to simply re-machine the heads. Dykem layout fluid was applied to the valve seats, and each seat was machined to match the lowest one. This ensures the installed height of each valve is the same.
Like the block surface, the...
Like the block surface, the heads were also given a cleanup pass on the deck. Minimal material removal still made it possible to use a standard copper head gasket.
The valves received a three-angle...
The valves received a three-angle grind of 30, 45, and 60 degrees.
Oscar Alvarez did all the...
Oscar Alvarez did all the work on the Hemi heads. Here, each valve was measured for installed height with a retainer and locks installed on the valve.
The spring pressure was then...
The spring pressure was then checked at open and closed heights. We're using COMP Cams springs, and our Moon Racing Cam calls for 130 lbs @ 1.700 inch and 372 lbs @ 1.150 inch with 441 lb/inch rate.
Two things were going on here....
Two things were going on here. First off, Oscar was installing the valve stem seals using a special drift and a mallet.
Second, you can see the valve...
Second, you can see the valve spring shims that were installed where they were needed. They come in various sizes and can be doubled up to maintain proper installed valve spring height. A pneumatic valve spring compressor is used to install the retainer and locks. The spring pressure against the retainer prevents the locks from ever budging.
The last step was to check...
The last step was to check the heads for any vacuum leaks. Everything checks out so it's on to the assembly.