Re: 400 runs bad

Posted by Bob M on April 01, 2002 at 07:13:01 from (165.170.128.65):

In Reply to: 400 runs bad posted by Trevor Martie on March 31, 2002 at 15:35:47:

Suggestions below are good. If those don't solve the problem here's a couple more possibilities to check:

1 - One (or more) valves has stuck open. Can verify with a compression check, or by removing the valve cover and inspecting valve motion visually. Often a stuck valve can be freed up simply by applying good penetrating oil to the stem, then alternately tapping the rocker arm to drive the valve down and CAREFULLY prying back up on the valve spring keeper. (Be sure the affected cylinder is on TDC compression before doing this....). If you find a valve which has stuck down, make sure the upper end of the pushrod is properly seated in the adjusting screw socket when you are finished.....I've found pushrods on stuck valves completely disengaged floating free in the motor on several occasions.

2 - The cam gear hub key has sheared which changes the valve timing. This happened on my Super M a couple years ago, and I encountered it again with friend's 400 this past weekend. In both cases the camshaft gear nut had worked loose (or unscrewed and fallen completely off in my case) allowing the cam gear to flop around and chew up the woodruff key in the gear hub. Suspect loading imposed on the cam gear by the live hyd pump cause the cam gear nut to work loose - even with a properly installed keeper under the nut. Unfortunately some major front end and motor disassembly is required to get at this one.

Good luck!

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