[Steve C.]

Cliff regarding the comparison between the Comp XR276HR cam and the Old Faithful cam with no other changes. Within your post #20 here you mention the XE cam pinged so hard it required rod bearing replacement before the dyno testing could continue.

Food for thought, prior to testing the OF cam can we presume they rebuilt the motor with new bearings and if necessary likely could have had the crank turned? In a roundabout way that in itself is a change. Could the damaged bearings affect the first dyno session with the XE cam ?

Example, during a chassis dyno session on a very mild 455 motor the Q-jet carburetor was replaced with a throttle body EFI system. They made a few dyno pulls with the EFI in place but something was wrong, it was found there was a bad injector in the throttle body. It was leaking by continually spraying. Not realizing that the engine was damaged at first, the throttle body was replaced. With no other changes they put the car on the dyno and made several pulls. Even on this mild of a motor, I was still down over 20+ rwhp, and that is when they realized the engine might be hurt. Without realizing it, the bad leak had washed down some cylinders, contaminating the oil. On tear-down, some rod bearings had gone bad. On this motor that may have been 350'ish flywheel HP, it was down 20+ rwhp with bad rod bearings - which would be maybe 30 HP at the flywheel.

Now on a motor making much higher horsepower the loss could be 50+ HP at the flywheel, maybe even more since it is operating at a higher RPM than the smaller motor, and such damage would cause more issues as the RPM increases.
Does that make sense?


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