PROJECT 632 PART 6:DELIVERANCE

With assembly complete, it was time to light the candle.

by Mike Mavrigian

all photos by author

Well, the motor was final-assembled and run on the dyno. Although we didn’t hit our hoped-for 1,200 horsepower, we did manage a 1,115 horsepower run. With further tuning, we know the potential is there.
First, let’s cover the final stages of engine assembly, involving the
ignition system, fuel system and vacuum pump setup.

DISTRIBUTOR

You may recall from our last issue that I accidentally ordered the wrong distributor from MSD (P/N 8558, the Pro Billet low-profile distributor). There’s nothing wrong with the unit, but the large five-inch diameter head wouldn’t clear our tunnel ram plenum box. I recently obtained a replacement (MSD P/N 85501).

This is one of MSD’s Pro Billet units, featuring a lockout (no mechanical advance). It should work well with our crank trigger setup. Upon checking distributor fit, I found that the nose of the bronze distributor gear contacted the block (touching a boss inside the block at about the 1 o’clock position as you stare down into the distributor bore). Instead of stripping back down to a bare block to grind clearance, I followed Scott Gressman’s advice by applying machinist blue to the bronze gear assembly, inserting the distributor as fully as possible and rotating the crank one full revolution. Upon removing the distributor, I noticed a contact path around the perimeter of the gear nose (not the gear itself, but at the very bottom of the gear assembly nose). Since my lathe was down, Jody Holtrey at Medina Mountain Motors in Creston, Ohio (a mere stone’s throw from my office) removed about 0.070 inches from the bottom of the nose. In addition, he reduced the outer diameter of the nose by 0.020 inches, from the newly-cut bottom, up 0.250 inches. Finally, the bottom nose area was radiused into a bullet shape. With the right rear oil gallery plug removed from the block, I could view the distributor shaft’s oil band location relative to the block’s oil gallery, verifying that the distributor shaft’s oil band was in the oil path.

I carefully measured the distance from the top of the intake manifold distributor boss to the top of the oil pump intermediate shaft, which measured at 8.096 inches. Knowing that I wanted 0.200 to 0.250 inches of distributor-to-shaft engagement, I then knew that the distance from the bottom of the distributor gear’s key to the underside of the distributor’s slip collar should be approximately 8.346 inches. This provided me with a rough distributor depth target.

I was able to adjust the distributor depth via the distributor’s slip collar to achieve
distributor-to-intermediate shaft engagement of about 0.225 inches. With the distributor bottomed out, I then raised the distributor (using the slip collar adjustment) about 0.010 inches. I then rotated the crank two full revolutions, removed the distributor and inspected the bronze gear for evidence of a contact pattern relative to the cam’s gear. Once I was satisfied with shaft engagement and gear mesh, I final-tightened the distributor slip collar.

Once all height adjustment was complete, I cleaned the distributor shaft and gear and applied a coat of Royal Purple Max Tuff engine assembly lube to the shaft, gear and engagement key before final-installing the distributor.

The MSD distributor was supplied with a pair of rubber O-rings for the shaft. While some guys don’t bother with the O-rings, I followed Gressman’s advice by installing only the upper O-ring, the theory being that the absence of the lower O-ring allows a bit of oil to dribble down to the shaft during engine operation.

I used the MSD distributor hold-down bracket P/N 8110. Due to the set height of the distributor, I ran out of clearance for this beefy hold-down clamp. In order to fit the clamp between the top of the slip collar and the chamfered area of the distributor underhead, I ground the tops of both clamp arms down by about 0.030 inches.

PLUG WIRES

The MSD 8.5mm Super Conductor spark plug wires were then routed along the
bottom of the heads and cut to length. The distributor-end terminals and boots were installed, and the wires were connected to the distributor cap following the special firing order required by the Crane billet camshaft. Our firing order is 1-8-7-3-6-5-4-2 (big block Chevy order, with cylinders 4 and 7 swapped).

Our selected spark plugs are Autolite P/N AR3932 (0.750-inch reach plugs, per Dart’s recommendation for the Big Chief II heads). I set plug gap at 0.024 inches (they were all close to this gap straight out of the box).

In order to provide extra protection for the spark plug boots and wires from exhaust heat, I installed a set of DEI’s new Protect-A-Boots. These “cool” booties feature an internal metal ring at the small end, allowing you to nudge the boot small end over the plug boot ends for a snug fit that insures good retention of the thermal-guard boots. This is a nice feature, eliminating the need to secure the boots with tie straps.

In order to provide a degree of tidiness to the plug wires, I used MSD’s plug wire
spacers (P/N 8841) to serve as wire separators. In addition, to prevent the wires from flopping around at the rear of the block, I made two 90-degree aluminum brackets using 1-inch-wide x 0.125-inch-thick aluminum strap that secure to the two rear intake manifold bolts and extend down across the rear faces of the heads. These brackets provided an anchoring base for a pair of four-wire MSD Pro-Clamp wire separator blocks (from kit P/N 8843). I secured one four-wire block to each aluminum bracket with one 10 x 32 button head screw (I tapped a 10 x 32 hole in each bracket).

She’s a tall bugger for sure, measuring 42 inches from top to bottom.

The engine is now equipped with an external vacuum pump and race alternator.

Tags: ASSEMBLY, DISTRIBUTOR, DYNO, MSD

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