Is anyone still using clay to verify P/V clearance?

[Charliesauto]

In the July 2018 issue of Car Craft, Robert Poole and Mark Magda have a very detailed 3-page feature article on how to check P/V clearance with clay.

Just me, but I gave up on clay in 1964 after being given a lesson by Bobby Allison. I'd read how-to-clay in Hot Rod and wanted to show my expertise. He said, "Clay is for kindergartners. You use it and tell me how much P/V we've got. In fact, do it on three different cylinders. You'll measure three different guesses."

Of course, he was right and he showed me how to do it with checking springs, degree wheel, dial indicator and a clipboard.

So how many of us still use clay?

Or do you use a dial indicator? If so, is TDC valve drop OK or do you degree wheel from 20 BTDC to 20 ATDC?

Or do you trust a computer program to verify P/V clearance?

We use clay and yes it is challenging to measure correctly, sometimes we have to make multiple attempts. Normally we use five balls of clay about .150" diameter to check the intake and three to check the exhaust.

Once we get an impression, we place a loose valve in the impression and use gauge pins to check the radial clearance.

We always check with the "real" springs, gasket and lash. We consider .070" intake and .090" exhaust to be our minimum with this method. And we like to see .050" radial.

I read an article one time where David Reher described the RM method and it sounded like a better way than clay, just never tried it. Maybe someone can find that and post it here.

[tenxal]

I like to use clay (with the race springs installed) for a visual and then a dial indicator.

http://rehermorrison.com/tech-talk-41-s ... right-way/

[gmrocket]

just another hint : Solder ( or Clay ) , can also show you if your Piston Flycut Notch Angle matches up exactly with your Valve Head's angle
by measuring top and bottom Solder contact thickness across the Valves diameter

Solder is just quick checking you can do on the Dyno with unknowns or uncertainties with Customers

You cannot insert or remove Clay on an Engine on the Dyno

unfurling a length of Solder thru a Spark Plug hole is easy , quick

remove the Headers ... shine a light in the Exhaust Port ... look thru the Spark Plug hole
insert the Solder across the Valve Notch ... turnover the Engine by hand .. pull out the Solder ... measure with a Dial Caliper if theres contact

Yep, solder has its uses. It's funny I find most people run way more clearance than thay need.

So true..piston manufacturers ask for the free drop measurement and the lift at different TDC points,, then proceed to cut the reliefs way deeper than you need..even if you moved the cam all over the place.

I don't know what formula they use buts it's usually way off...learned to tell them what depth I want for initial valve relief depths..

I have an old piston I cut most of the dome off, I put putty on it and rotate it through the max cam variances...pull the head and measure off the block deck what I want . If it's wrong I'm to blame.

[MadBill]

...
So true..piston manufacturers ask for the free drop measurement and the lift at different TDC points,, then proceed to cut the reliefs way deeper than you need..even if you moved the cam all over the place....

Probably a CYA move. Too shallow, they get rained on when there's a coming together; too deep and no one gets hurt...

[Travis Horton]

One time I used a Tootsie Roll to check radial and depth when my niece "borrowed" my clay!

[mk e]

I run 5mm valve stems....I think solder would tweak the valves....looking at them wrong seems to tweak the valves.

So clay after everything checked good with and a dail indicator and degree wheel.

[MadBill]

Tip for skinny valve users: Hollow resin core solder deforms easier.

[rp930]

It’s worked for decades and still works today.

[bmcdaniel]

I use Silly Putty with a little oil on it.

[kirkwoodken]

I cover the clay with a piece of zip-lock plastic baggie. Doesn't stick to anything that way. You can roll "snakes", cover them with plastic and stick through plug hole.

[RTR-1]

Has any of you guys tried the LSM On Head Valve Spring Tester with their piston to valve checking attachment? It suppose to allow you to check P to V on a assembled engine with a dial indicator.
Thanks!

[houser45]

I only use clay for radial clearance, i use checking springs at zero lash too check p/v clearance. I have an intake and exhaust amount that i am comfortable with and it all varies on valvetrain weights, rpm amount and usage. I dont like using the actual springs because the amounts will change from the difference of rocker arm/pushrod deflection or the amount of toss in the valvetrain. Probably no right or wrong method it’s whatever you feel comfortable with and what measurement you feel comfortable with .

[DrillDawg]

On some heads, you stack it up with no head gasket and no lash, leave the exhaust valve out, put a light in the intake port, snake your favorite solder wire though the exhaust port, do your 20 deg on each side, then measure and calculate. You get a visual, racial and P to V, sometimes you have to look/work through the spark plug hole.

[engineguyBill]

Clay is still a useful tool for checking valve/piston clearance - after all these years.

[dwilliams]

Clay is the only way to do it.

10-4. Clay doesn't just tell you how much, it can also tell you if the piston maker put the reliefs in the right spot... and with today's "improved" heads, the valves aren't necessarily where the piston maker might have expected them... That's not even getting into changes in the valve angles.