Friday, August 13, 2010

Engine Tear-down

After the lousy engine performance at ORP, I felt there was nothing to lose by tearing apart the engine to get to the root of the problem. Taking the head off revealed the effects of the unstable timing, carbs challenges, and eminent head gasket failure.

It didn't take long to locate the root cause of the poor performance. Removing the timing cover this time revealed heavy gouge marks. Not only was the cam gear grinding on the cover, but the timing chain was getting into the act too and over an 1/8" of the reinforcing rib on the inside was ground away. "Why?", I asked.

I took hold of the cam gear and the whole cam shaft would move in and out of the block some .130". I'm no pro engine builder with countless builds under my belt, but even I could see that that wasn't right. Since there's a helical gear on the shaft that drives the distributor, it was easy to understand why the timing wouldn't remain stable.

Some more disassembly revealed that the woodruff key was forced out the back of the slot when the cam gear was jammed on. This kept the cam gear from bearing against the block as it should. Thus, the shaft would slide in and out at random, and take the distributor setting with it. Flat on the ground without load, the engine would time and run well. Race it up or down a hill, and it would crap out.

And now, the train wreck picture show......

Woodruff key jammed half way out of the slot

Should the side of the cam bearing be ground into like this? I doubt it.

Another angle. And pistons 3/4.

Pistons 1 and 2

Another head gasket for the trash. And the buildup on the valve area.

1 comment:

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