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

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Charliesauto
Member
Member
Posts: 105
Joined: Wed Sep 03, 2014 2:01 am

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

Post by Charliesauto » Thu May 03, 2018 5:18 pm

PackardV8 wrote:
Thu May 03, 2018 1:02 pm
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
Pro
Pro
Posts: 441
Joined: Sun Nov 17, 2013 8:48 pm

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

Post by tenxal » Thu May 03, 2018 5:29 pm

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
Guru
Guru
Posts: 1384
Joined: Wed Nov 12, 2008 6:40 pm
Location: Grimsby Ontario

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

Post by gmrocket » Thu May 03, 2018 5:57 pm

statsystems wrote:
Thu May 03, 2018 2:41 pm
maxracesoftware wrote:
Thu May 03, 2018 2:22 pm
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.

User avatar
MadBill
Guru
Guru
Posts: 13445
Joined: Tue Nov 15, 2005 10:41 am
Location: The Great White North

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

Post by MadBill » Thu May 03, 2018 11:12 pm

gmrocket wrote:
Thu May 03, 2018 5:57 pm
...
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...
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.

Travis Horton
Member
Member
Posts: 78
Joined: Tue Jun 08, 2010 11:50 pm
Location: Pittsburg, KS

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

Post by Travis Horton » Thu May 03, 2018 11:21 pm

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

mk e
Guru
Guru
Posts: 4289
Joined: Mon Sep 17, 2012 3:19 pm
Location: Elverson, PA

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

Post by mk e » Fri May 04, 2018 10:15 am

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.
Mark
Mechanical Engineer

User avatar
MadBill
Guru
Guru
Posts: 13445
Joined: Tue Nov 15, 2005 10:41 am
Location: The Great White North

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

Post by MadBill » Fri May 04, 2018 1:08 pm

Tip for skinny valve users: Hollow resin core solder deforms easier. :)
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.

rp930
Member
Member
Posts: 98
Joined: Tue Dec 10, 2013 11:47 pm

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

Post by rp930 » Fri May 04, 2018 2:00 pm

It’s worked for decades and still works today.

bmcdaniel
Pro
Pro
Posts: 272
Joined: Wed Feb 21, 2007 3:30 pm
Location: York, PA

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

Post by bmcdaniel » Sun May 06, 2018 1:27 am

I use Silly Putty with a little oil on it.

kirkwoodken
Guru
Guru
Posts: 1525
Joined: Thu Dec 06, 2007 11:35 pm

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

Post by kirkwoodken » Sun May 06, 2018 2:42 am

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.
"Life is too short to not run a solid roller cam."
"Anything is possible, if you don't know what you're talking about."
I am NOT an Expert, and DEFINITELY NOT a GURU.
Kirkwoodken

RTR-1
Member
Member
Posts: 93
Joined: Wed Jan 11, 2006 10:34 pm
Location: Oahu, Hawaii

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

Post by RTR-1 » Sun May 06, 2018 3:48 am

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
Member
Member
Posts: 125
Joined: Thu Apr 24, 2014 10:05 pm

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

Post by houser45 » Tue May 08, 2018 10:54 am

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
Expert
Expert
Posts: 980
Joined: Tue Jul 06, 2010 11:03 am

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

Post by DrillDawg » Tue May 08, 2018 11:16 am

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.
BORN RIGHT THE FIRST TIME

engineguyBill
Expert
Expert
Posts: 883
Joined: Fri Feb 26, 2010 11:15 am
Location: Gold Canyon, AZ

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

Post by engineguyBill » Tue May 08, 2018 12:58 pm

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

SAE Member (28+ years)
ASE Master Certified Engine Machinist (+ two otherASE Master Certifications)
AERA Certified Professional Engine Machinist

"Do what you can, with what you have, where you are."
- Theodore Roosevelt

dwilliams
Guru
Guru
Posts: 1008
Joined: Sun Oct 15, 2006 10:00 am

Post by dwilliams » Tue May 08, 2018 5:48 pm

statsystems wrote:
Thu May 03, 2018 1:12 pm
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.

Post Reply