1968 GMC Inline 250 Valve Adjustment

[68gmcdude]

Hi All...
I have a slight clicking/clacking noise so I'm thinking the valves may need adjusted. I found some older posts I've been reading but I saw conflicting information. Some say to tighten the nuts an additional 1/2 half turn after reaching zero lash and some say to tighten 1 full turn. Also, some say to tighten the additional turn with the motor running and some say to tighten after turning to motor off. With that being said, the GM shop manual says to tighten each nut four 1/4 turns, 10 seconds apart (for a total of 1 full turn) while the engine is running. That was back in 1968 so the thinking may have changed. My motor is all original with 55k miles. Looking forward to the advice.

[Steeveedee]

I've always adjusted hydraulic lifters as the manual you cite specified.

[RustyPile]

I've always used the "one turn" method on new lifters and "half turn" on used lifters.. Never had a problem with either method...

[Ol Blue K20]

Originally Posted by RustyPile

I've always used the "one turn" method on new lifters and "half turn" on used lifters.. Never had a problem with either method...

X2, 1/4 turn at a time.

[RichardJ]

They so seldom loose that adjustment, you may want to do a little investigation to determine the cause.
Several years ago I had a problem with the stock push rod ends. Cam is considered mild and rocker geometry is good. I replaced the rods with ones that had what I think have a nicer machined end. Similar to ones in the 2nd image from the web.

Chevy inline six rockers are 1.75 compared to SBC 1.5 ratio.

You can't go wrong with the manual method of cold adjustment with the engine stationary. Half at TDC and the rest after rotating 360*. One half turn below Zero lash