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Valve lift specifications

00Dan

Well Known Member
I’m interested in checking my valve train to see if it’s opening sufficiently for the engine to make rated power. I really don’t want to pull a cylinder at this time and I’ve previously read about removing the rocker box covers and measuring intake valve lift to detect a worn cam lobe. However, I cannot find the specification for the measurements anywhere.

Does anyone know what the measurements should be on an O-320, or know which source document details it?
 
Table of limits

If you look to the table of limits in your engine model overhaul manual, you should be able to find cam lobe dimensions. You should be able to find it on the lycoming website. If you dial the pushrod side of the rocker, you should get a decent view of the cam lobe dimension EXCEPT anything that’s being given up in hyd lash. I can’t help you there, to do that I think (75%) the right number is dry tappet clearance, which is invasive unless it’s an H2/T mod.

Dial all of them at the rocker or pushrod and compare. That should at least give you a comparative number as a diagnostic.

I’m looking forward to the thoughts the gurus might offer on the lash topic.
 
If you look to the table of limits in your engine model overhaul manual, you should be able to find cam lobe dimensions.

This is incorrect. Lycoming, for some strange reason, does not publish specs in any table of limits for lift or cam lobe dimensions.
 
Just measured the lycoming 320 cam I have here and the intake lobe is .348 inch lift and the exhaust lobe is .348. Both the same at the cam lobe.
 
Not that I had any reason to doubt him….

Bob, as usual, is correct, and I bow to his experience and wisdom. SSP-1776 does not have cam lobe info, only cam to case clearance info. Details you don’t remember after a while….
 
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