Jim Smart
October 1, 2009

Last month, we took you through the tear down and inspection of Gary Schweitzer's '65 200ci six-cylinder engine at JGM Performance Engineering. We learned during the process that 35,000 original miles doesn't always mean pristine. Much depends on how the engine was treated. Gary's six-cylinder was loaded with sludge due to a lack of oil changes at a time when leaded fuel and antiquated lubrication technology worked against engine life. This made his engine very typical of the time period it was operated in. Removing tetraethyl lead from gasoline made a significant difference in the environment - and engine life. Advanced engine oil technology has made a difference too.

JGM Performance Engineering has cleaned up Gary's castings and all machine work has been accomplished. JGM employs an environmentally-friendly cleaning process that also leaves castings looking pure, like they just came out of the foundry. We tried to get away with a .020-inch overbore on Gary's block but because the engine sat over 30 years, the cylinder walls were severely pitted. In fact, the #1 bore had to be sleeved because pitting was so bad that it would not clean up at .030-inch oversize. Gary's crankshaft had to be ground .010-inch undersize and returned to service with .010-inch oversize Speed Pro bearings from National Parts Depot.

On top, Gary's cylinder head was about as expected. It needed new valves and guides. Exhaust valve seats were cut out and hardened steel seats installed for use with today's unleaded fuels. Here's the rule of thumb for exhaust valve seats: If you're going to drive your Mustang regularly, install hardened exhaust valve seats. Seldom-driven show cars don't need it.

JGM did a nice multi-angle valve job that not only improves air flow, but valve cooling as well. More contact surface is better when it comes to valve life because there's improved heat transfer. JGM uses Viton valve seals on all of its engines because they have been proven to outlast Teflon and those old umbrella seals. Special cylinder head machining must be performed to accommodate the Viton seal, but it's worth every penny.

Important Details
People generally associate painstaking detail with high-performance engines, but it must apply to all engine builds. If you disagree, ask yourself how much time you have to pull an engine and do it all over again. Or worse, have to find another block or cylinder head because the engine got trashed. Do it once and do it right.

Two things you must check - true cam timing and piston deck height. Brand-new, out-of-the-box does not mean it's safe for installation and use. All parts must be checked with close inspection and tolerances. Pistons, for example, can be off significantly, adversely affecting compression and piston-to-cylinder head clearances. If there's too much deck height, you wind up with compression that's too low. If pistons measure "out of the hole," so to speak, cylinder head contact is certain.

Important To Success
Jeff Latimer of JGM Performance Engineering is a craftsman and engine architect. Although Jeff doesn't typically rebuild distributors, he rebuilt our Autolite Load-O-Matic single-point distributor. He tore it apart, tossed its sum total into a parts tumbler, and reassembled it for us using new Motorcraft parts from National Parts Depot and Scott Drake Reproductions. Because it is a low-mileage distributor, the shaft and bushings checked fine.

What About Valve Lash?
When we tore down Gary's six-cylinder, we found adjustable rocker arms and cup-style pushrods. This went against what we knew to be true with FE-series big-blocks and 170/200ci sixes with hydraulic lifters. It turns out Ford sixes with hydraulic lifters were fitted with both adjustable and non-adjustable rocker arms depending on what was available at the time of manufacture. When we checked with Speed Pro, we learned the only type still available new is the adjustable type, which is what they sent us.

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