Ryan Peart of JGM tells us...
Ryan Peart of JGM tells us it's always best to install the camshaft first, whether it's a V-8 or a six. This allows easy cam access and minimizes the risk of cam lobe journal damage. Cam journals are coated with engine assembly lube, which has staying power. The lobes must have molybdenum grease (also called moly coat) for proper flat tappet cam lobe hardening when the engine is fired.
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.
A one-piece rear main seal...
A one-piece rear main seal is not available for 170 and 200ci sixes. However, Ryan shows the process of staggering two-piece seal gaps away from main cap parting lines to minimize chance of oil leakage. He uses The Right Stuff sealer on block contact surfaces, which virtually eliminates any chance of leakage.
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.
Speed Pro .010-inch oversize...
Speed Pro .010-inch oversize main bearings have been set and our crank readied for installation. Ryan has measured both journals and bearings for absolute certainty about clearances. Although some think it absurd, we suggest checking everything three times. And if you have a qualified second set of eyes, have them check your work.
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.
 |  When you torque main and rod...  When you torque main and rod caps, you are compressing the bearings into a perfect circle. Bearing tabs exist solely for alignment purposes, not security. Surfaces between bearings and block (or rod) must be dry for the bearing to stay put. Main cap installation and tightening must be performed in phases. Snug the cap first to ensure accuracy. Torque first to 35 ft. lbs., beginning with the inside main caps and working outward to #1 and #7 main caps. Then, torque to 60-70 ft. lbs. Go back and recheck torque. |  Crankshaft endplay must always...  Crankshaft endplay must always be checked. With the 170 and 200ci six, endplay is 0.004-0.008-inch with a maximum allowable amount of wear at 0.012-inch. Endplay affects everything along the crankshaft. When endplay is excessive, you are courting trouble due to poor alignment issues. By the same token, it must not be too small, creating risk of cease up. |
 |  Piston/rod installation calls...  Piston/rod installation calls for rod-bolt protectors and two careful installers, one at the top and another down below to make sure the rods don't contact the crank. Otherwise, there's risk of nicking a crank journal. Connecting rod bolts have been replaced with new ARP bolts. Rod bolt torque is 19-24 ft. lbs., done in half values. First, 12 ft. lbs., then a full 19-24. Threads must be lubricated first. Be sure to check connecting rod side clearances - 0.0035 to 0.105-inch, which is huge compared to V-8 connecting rod side clearances. |  Piston crowns, along with...  Piston crowns, along with compression height, determine compression ratio. Ford dished pistons to control compression ratio. A flattop piston makes more compression than a dished piston (shown). These are Speed Pro cast aluminum oversize pistons (3.710-inches) from National Parts Depot. |