Using feeler gauges

[slug]

When checking valve clearance with feeler gauges, how do you tell when the clearance is right? Should the feeler gauge go freely between the rocker and the valve, or should there be a slight resistance? I've done my valves many times before and always went with a slight resistance (that's what I was taught back in my welder/fitter days), but I'm curious what other people think/do.

[Baldini]

When it feels like it's sliding on both surfaces but not pinched.

 

KB

[dlaing]

When it feels like it's sliding on both surfaces but not pinched.

 

KB

Well put!

I have probably aimed for tiniest amount of pinch that I can detect, but technically I think Baldini is more correct.

The old dogs tale is to equate pulling through a dictionary, but that is too variable and implies some pinch.

I verify my methodology by going one smaller and one tighter. One smaller should feel too loose, and one bigger should not fit...assuming a difference of gauges of 0.05mm (.002") or greater.

Be sure your pull is parallel.

Be sure to use good, not too battered and not too corroded gauges, and verify at different places on the gauge.

It does not have to be perfect. Just don't mess up and set it at the wrong TDC position.

[Lex]

I'll add something I learned from a very experienced BMW mechanic years ago: When you take the reading push down on the end if the rocker opposite the valve. There are a a lot of places that can have some slop (cam to follower, follower to push rod, push rod to rocker) and throw the reading off. Once you do that Baldini's description of the feel of the of the feeler gauge is pretty good.

[mark.gilmore]

Thats how I do it.

[dlaing]

I'll add something I learned from a very experienced BMW mechanic years ago: When you take the reading push down on the end if the rocker opposite the valve. There are a a lot of places that can have some slop (cam to follower, follower to push rod, push rod to rocker) and throw the reading off. Once you do that Baldini's description of the feel of the of the feeler gauge is pretty good.

Thanks! That makes perfect sense! (and may explain why my readings go off so fast )

[slug]

Thanks all.

 

Great advice on pushing down on the opposite side of the rocker. Someone mentioned that somewhere on this forum many moons ago, and I've done it ever since.

 

[Molly]

Thanks all.

 

Great advice on pushing down on the opposite side of the rocker. Someone mentioned that somewhere on this forum many moons ago, and I've done it ever since.

 

 

Helps to have three hands. I also need to find a tool to hold things in place whilst I tighten it up. I always move it just enough to have to do it again... Doh!

[Dan M]

"Go / No-go" is an easy check. Set it to spec with light drag. Check it with the next size up. Should be quite tight. The next size down should be very loose.

No need to do every valve like this but you will get the "feel" for what is right after checking a couple.

 

edit: This assumes you have a feeler gauge set, not just the spec sizes.

[tmcafe]

Helps to have three hands. I also need to find a tool to hold things in place whilst I tighten it up. I always move it just enough to have to do it again... Doh!

Holding the adjusting screw in place is bit awkward. I used a smaller adjustable wrench, but later somebody gave me a 1/8" mini wrench (Snap-on), which should fit the screw head.

[tmcafe]

edit: This assumes you have a feeler gauge set, not just the spec sizes.

I have a metric set, but the specs I used (Micha's best recommendation) aren't among the blades, so I "cheated" by adding two blades to match. I wonder if some of the inch sets have a close match.