How to measure valve guide wear?????

What is the proper way to tell is your valve guides are worn past their limit? How do you measure it? Pull the valve out a little, hook at dial indicator to it and jiggle the valve?

 

That's one way. The method I use is to check the ID with a small dia. inside micrometer, mic the outside of the valve stem, subtract the two and you've got your clearance. After doing this for over 20 years you get a feel for it, and seldom need to do the micrometer thing.

Frank

 

Small hole gauges, then mic them. They are not to expensive, Starett makes them. Tim

 

If you've got access to a lathe you can make a gauge. Just a length of round bar that is turned to the maximum size of wear. If it slips in either end of your valve guide, you are over size.
Ideally you should mill or grind two flats on either side of the gauge, leaving about a 1/3 of the bar thickness remaining, so that you can still get an accurate reading if the guide is worn oval.

 

Ok, I made a setup with a large C-clamp to hold the dial indicator (aluminum heads). i think I have around .003" Should I hole the valve out a hair off of the seat? I have the dial indicator on the side of the valve stem, just above the groove for the keeper. It is seting 908 to the vale, in the same plane as the rockerarm would be. I figured this would show the most wear. All I have is specs for the stock 289 heads, and they say intake: .0010-.0027 wear limit .0045 exhaust: .0020-.0037 wear limit .0055. I ***ume they are cast iron guides on the stock heads. These are a "special manganese bronze alloy". Would the spec be the same?

 

I'd try and get the dial indicator tip as down and close to the valve guide as you can, else your wear will be magnified by the length of the valve stem the further away you get from the guide (if that makes sense)

Lift the valve slightly out of the seat as you measure, so it doesn't cause false readings.

I ***ume the wear limit will be the same no matter what the guide material, as the idea is to keep the valve as true to the seat as possible as the valve operates at a zillion moves a minute.

I'm no engine builder expert but I spent years as a machinist and inspector when I was younger.

 

Yes, I realize this thread is almost 20 years old...

I did some measuring on valves and guides this weekend using a mic and a split ball gauge. One thing that confused me - if you subtract the OD of the valve from the ID of the guide, you get a number that is called valve to guide clearance but your actual clearance is half that, right?

Example - on my 7.3 IDI diesel engine on one cylinder I was getting a valve guide ID of .3739" and the OD of the valve is .3719" for a difference of .002". If you used a feeler gauge to measure this, you'd actually get .001", right (***uming the valve didn't move laterally within the guide)? Despite this, the clearance is expressed as .002", correct?

 

1 for 1 side and 1 for the other side =2 but if you measure 4 sides it is not 4 it is still 2

 

Correct. But is the clearance expressed as .002" or .001"?

 

2 total 1 for each side

 

Not to hijack but does that 2X logic apply when measuring main and con rod bearings using a micrometer and snap gauge?

 

Cylindrical fits are always based on diametral clearance or interference. .001 clearance means the hole is .001 larger than the shaft. A .001 press fit would mean the hole is .001 smaller than the shaft.

 

^^^this^^^

Building press fit gun barrels, clearances are always measured as total on round surfaces.

.

 

Ok, that makes sense. Ford's specs for factory new was around .0021" (with minor variation) so if I'm getting somewhere in the neighborhood of .0020" on a super low mile engine, that sounds right.

 

FWIW, used valve guides are never round. They're always hour-gl***-shaped in line with the valve stem and pushrod. It's almost impossible to get accurate measurements externally. Even internally, with a $2500 Sunnen valve guide gauge set, it still takes experience, as the guide is worn differently along the length.


Today's chrome stem valves and better alloy guides last much longer than in the bad old days. However, since there's no lead in the gasoline and very little zinc, et al, additives i the oil, we can't run rebuilt valve guides as tightly as we used to, unless they're rebuilt with silicon bronze guide liners.

jack vines

 

Thanks, Jack. I did find that measuring the ID was tricky; suspect it gets easier with experience.

 

On a similar note, I've seen NEW guides come in NEW aluminum heads, that were "barrel" shaped, from poor machining practices.
These cylinder heads went back to the manufacture. Replacements were 90% better !

If you can, "always" check, especially on performance or race engines.

Mike

 

I have a complete set of gauge pins from 1/64" to 1/2" that I can push into the guide once the valve is removed. Compare the valve stem reading with my micrometer to the gauge pin size and I know the exact clearance. It's pretty simple, but the set of gauge pins aren't cheap. Luckily mine are old and paid for long ago.

 

I had a set of bare double hump heads given to me by a friend. I quick checked the guides with an 11/32 drill shank. I had one hole the drill rattled around pretty good. If I remember right, the next size up even started to go in. An example of free not being cheap. Glad I saved them, though.

Gary