Next on the agenda was the tear down. The carb was removed and packaged for storage, as we plan on using it once the rebuild is complete. Then Rolenc removed the intake manifold and valve covers. The valve lash was set hot on the dyno at 0.020-inch. He remeasured lash before digging into the heads and most had dropped to 0.016-inch, but two (No. 1 and No. 2 exhaust valves) had not tightened as much as the rest, measuring 0.019- and 0.020-inch respectively. Rolenc tells us this is because the coolant passages in the heads give the ends different cooling properties and this is normal.

Next was a leak-down test. Seven of the eight cylinders performed well, showing between 1- and 4-pecent leak-down. Cylinder No. 4, on the other hand, was a different story. As soon as compressed air was introduced to the cylinder, the gauge jumped to 40 percent, and you could hear the air escaping. After a little investigative work, Rolenc determined that both the intake and exhaust valves were leaking. This explained why this cylinder's EGT was almost 100 degrees hotter than the rest of the engine on the dyno.

With the leak-down test complete, the heads came off. Rolenc quickly removed the valves from the No. 4 cylinder to find the source of the excessive leak-down. Using a concentricity gauge (valve guide runout), Rolenc measure the exhaust valve seat at 0.008 and the intake at 0.0092. SAE standard tolerance is 0.002, and SRE uses 0.001 as its standard, so these are very far out of spec. Consequently, combustion gasses are allowed to bypass the valve back into the intake side of the cylinder head and intake manifold.

After taking some time to examine the cylinder heads, we came to the conclusion that at some point in the life of this engine, it had blown up in a big way. One intake port in the cylinder head had been welded (and not by a trained professional), and there was one odd-ball pushrod. The weld job looked as if the head was welded while still on the block. And to make matters worse, not much was done to match the port to the rest of the head. The lifter bores in the block had been sleeved, which initially we looked as a smart move by a good engine builder, but once we learned more about this engine's checkered past, it may have been done as a repair from a near-catastrophic failure.

Shifting our attention to the bottom end, Rolenc removed the oil pan and turned the engine over. At first glance, everything looked good, as the rotating assembly consisted of a Scat crankshaft, Carrillo rods, and SRP pistons. All of the internals were on the old side, which isn't necessarily a bad thing. Rolenc's concern is that these components could be on the heavy side, and lighter components would work better. The crankshaft had some weight removed and some weight added (from the looks of it by the same guy who tried to fix the cylinder head).

Once we take a closer look at each component individually, we will be able to figure out what we can keep and what will be replaced.

Schoenfeld Headers
Holley Performance Products
1801 Russellville Rd., Dept. PHR
Bowling Green
KY  42102-7360
MSD Ignition
SRE Engine Techniques