Claying pistons for clearance

[digger]

IMO you dont normally need a very accurate measurement with clay for P to V as most people arent trying to optimise it , rather just check there is enough so clay is good enough.... with squish clay is likely not going to be accurate enough if youre trying to get it accurate within 0.05-0.10mm or so on a performance engine its easy to squish it a bit much with verniers or not enough...

[ForcedFirebird]

Well, yes, but big enough solder to check valve clearance would scare me.
In the gut reaction department, putting metal in the path of an opening valve makes me go 'errr....'
I'm paranoid about bent stems, just because I seem to have bad luck
with 'em. Set a head down wrong with the cam in it, once...





t

I rebuild m20 heads nearly on a daily basis. I have only bent a couple valves and that was because I was in the hurry and used the old hammer and socket trick to rapidly disassemble one - and that was only because I didn't use the brass hammer to break the retainer/lock seal. Too much of a hurry and that won't happen again. Good thing I have a box full of m20 valves, or I would have been cursing up a storm lol. The bends were so slight, didn't even notice until they were being back cut.

As far as the solder, it's not like you are sticking a 1/2" piece in there - just something close to get it to smash a little. Plus, when turning the engine over slowly by hand, pretty sure you would feel if it were too much and back off (one would hope). It takes a lot of force to bend a valve, a normal sized ratchet/wrench would make that very difficult. You could also use tin foil if the solder made one too nervous. Clay is just far too difficult for me to get an accurate measurement, even with calipers.

[zaq123]

Well, yes, but big enough solder to check valve clearance would scare me.
In the gut reaction department, putting metal in the path of an opening valve makes me go 'errr....'
I'm paranoid about bent stems, just because I seem to have bad luck
with 'em. Set a head down wrong with the cam in it, once...



Hmmm? that's the point of a clearance check- you put something in that WILL be
in interference, and measure how much it deforms. I believe John that solder's soft
enough, I'm just too chickenshit (and I do few enough engines) to use it instead of clay.

t

I think you guys are talking two different things, quench clearance check and valve clearance check.....so it appears

[TobyB]

Solder is far softer than your valves.

Well, yes, but big enough solder to check valve clearance would scare me.
In the gut reaction department, putting metal in the path of an opening valve makes me go 'errr....'
I'm paranoid about bent stems, just because I seem to have bad luck
with 'em. Set a head down wrong with the cam in it, once...

If your valves are sticking out that far that you damage them while doing a clearance check, you were going to have a bad time anyway..

Hmmm? that's the point of a clearance check- you put something in that WILL be
in interference, and measure how much it deforms. I believe John that solder's soft
enough, I'm just too chickenshit (and I do few enough engines) to use it instead of clay.

t

[zaq123]

Solder is far softer than your valves. I use this method without any bad results. I have even checked assembled motors before taking them apart this way.

Yeap, Solder through spark plug works well if one knows what he is doing. Also BH of solder is about 10 vs 85 or so of aluminum head, valves being much harder.

[ForcedFirebird]

... solder for squish makes sense. Valves might not like it, tho!

heh

t

Solder is far softer than your valves. I use this method without any bad results. I have even checked assembled motors before taking them apart this way.

[nando]

If your valves are sticking out that far that you damage them while doing a clearance check, you were going to have a bad time anyway..

[TobyB]

... solder for squish makes sense. Valves might not like it, tho!

heh

t

[ForcedFirebird]

The squish area is angled. The outside ring is where you want to measure, and I have found they like to have .045". Check more than one cylinder if the head has been shaved, sometimes they were warped in the past and have different measurements between them.

Also, I prefer to use electrical solder rather than clay. It will smash down and can easily be read with a caliper.

Typically the piston will contact the head before the valve does - unless you have a high lift cam etc.

[zaq123]

Clay area for the valve clearance is pretty self explanatory.
What about quench clearance for m20b25 type pistons? Where is the best spot on the piston to put clay to get these measurements? Am I correct to assume that its top ridge is the closest piston's area to the head?
If someone got pics, that would be very helpful.