i am looking to find out what the max cam i can install without valves hitting my pistons, on a stock L98 Short block. I was told to bolt the head on "temp" with gaskets installed, with clay on the piston. then rotate the assy to push the valves into the clay for measuring. Is this how it's done? SHAGGY

 

Sounds about right to me.

Robert

 

yup

 

That way of determining piston-to-valve clearance SUCKS!!!!!!!!!!!! Do not use this method to determine valve-to-pistion clearance.

How do you get a cross section measurement of the imprinted clay material. Remove the clay (it streches), cut it which compresses the material, then try to meaure it. Not very accurate.

Here is the procedure to do it. With "checker" valve springs, this procedure will work for either a solid or hydraulic lifters.

Checking Piston-To-Valve Clearance
With Heads Installed
If the heads are on the engine, you can check the clearance using a degree wheel, a dial
indicator with magnetic base, a hand style valve spring compressor, and two valve checking
springs.
Use the following method for measurement:
1. Remove Rocker Arm Covers
2. Remove Fan, Fan Shroud, Belt(s), and Crankshaft Pulley.
3. Remove Spark Plugs.
4. Determine Top Dead Center on Cylinder Number 1 using a degree wheel.
5. Remove Intake and Exhaust Rocker Arms From Cylinder Number 1
6. Remove Intake and Exhaust Valve Springs From Cylinder Number 1
7. Install Checking Springs.
8. Install Dial Indicator directly above intake valve, and set between .300 and .400.
9. Note reading on paper.
10. Rotate Engine to 15 degrees before top dead center (15 BTDC).
11. Press down on valve until valve meets piston. Note reading on paper.
12. Subtract value from Step 11 from value in Step 8. This measurement is TC in the formula below.
13. Repeat steps 10 thru 12 at 10 BTDC, 5 BTDC, 0 TDC, 5 ATDC, 10 ATDC, 15 ATDC
14. Repeat steps 5 through 8 for exhaust.
15. Install dial indicator tip against hole in intake pushrod ball.
16. Set dial indicator between .000 and .100. with lifter on heel of cam (base circle).
17. Note reading on paper.
18. Rotate Engine to 15 degrees before top dead center.
19. Note dial indicator reading. This measurement is LL in the formula below.
20. Repeat step 17 at 10 BTDC, 5 BTDC, 0 TDC, 5 ATDC, 10 ATDC, 15 ATDC
21. Repeat steps 13 through 18 for exhaust.
22. Apply these measurements to the formula below.

Where:
Total Clearance, Seated Valve To Piston = TC
Cam Lobe Lift Measured at Lifter = LL
Rocker Arm Ratio = RR
Piston to Valve Clearance = VC

Apply This Formula:
TC - (LL x RR) = VC


And a pic (sorry it's a Mopar)



Any other way is WRONG! How do I know this???

 

Very nice

 

btt