Re: screwed up crankshaft for my 32

Posted by 32model901 On 2010/5/4 13:51:52

One addition comment that may be helpful when having the engine rebuilt:

I had a reputable engine builder bore & pour the major stuff so I could finish the job and save some $$$$. The engine builder looked at the camshaft. They polished the cam lobes, no wear was evident thanks to the roller rockers.

I finished assembling the engine and couldn't get it to run right. I finally ended up measuring the cam lift per lobe as I rotated the cam because of difficulty adjusting to .006 clearance.

I discovered a few of the cam lobes were not located on the center axis of the camshaft. Even though the cam lobes looked perfect, because they were bent off center it was impossible to adjust to .006 tappet clearance. As I rotated the cam I was getting some valve lift even when I wasn't on the cam lobe.

This required I pull the block off the crankcase and remove the cam, which was sent out for straightening and re-grinding.

Lesson learned - DO NOT let any machine shop tell you your cam is OK just because they don't see or measure wear on the cam lobes.

Lift for each lobe can be determined by measuring the base circle of each lobe and subtracting it from the overall lobe height.

The lift per lobe on my cam was within .002, but since some of the lobes were off center .011, it was impossible to adjust to .006 tappet clearance.

If you're not having your camshaft re-ground ask your engine re-builder to inspect the cam and give you base circle and lift measurements for each lobe with the cam set on vee-blocks and rotated on it's journal's.

This is the only way you will know each lobe has the correct lift and is positioned correctly to the center of the camshaft journal bearings.

Dave