KB 96 (2056) fly cut valve notch, 8 notches: 4 intake and 4 exhaust ...Pics and instruction Options

[rfinegan]

After the engine fail on my 2056 the investigation began measuring the piston the valve clearance. I tried the clay/ Playdoe method and the results were not as good as I would like. So i set up the failed Number 1 piston with the smiley (IMG:style_emoticons/default/smile.gif)


I set up the head from the other side without the bent valve and used the rocker shaft spring (just a light weight spring I had handy)to push down the valve till contact was made with the piston and the cam lobe was starting open the intake. At about 10 degrees on the degree wheel the closest reading was 0.080. ( this was in the small indentation made by the valve failure)

I tilted the mill head to align with the valve guide and set the piston in the v blocks and used my 123 blocks to center the piston pin.


I indexed the center of the intake valve with a pencil to set the Y axis on my Bridgeport.


Centered on the mark, I now had to find the correct x axis. Since I already had the mark from the valve on the piston, I set the fly cutter .100 more than the diameter of the 44mm valve. The marked put the piston top was indexed and moved my X axis in to touch the previous valve mark. I then moved my X axis .050 inch and confirmed my zero to the cutter.

I moved my Knee (set to zero) .050 inch to make the first cut. The piston crown of the KB measured at .220 ( for a min .170 thickness). This feels like a safe depth and puts my clearance at .130.

I will repeat the process on the 2 valves notches with no "kiss' marks by marking up the piston tops with marker and using the valves to get the reference mark by hand

[rfinegan]

I am going to walk through this process One MORE TIME! Well I get to do it 4 times for the intakes( and 4 for the exhaust if needed)

1)Remove valves from head and assemble with torque spec

2)Rotate crankshaft to TDC (see degree wheel )

3)Insert pencil to mark centerline of valve on top of piston

4)Center punch center line location for Posterity

5) Using V blocks mount piston to vice with business cards to protect
a) Use the piston pin to parallel blocks ensure the piston in pin is perpendicular to the vice
6) Center the Quill to the reference valve center line in piston and lock the X/Y tables

7) Insert cutter in collet and check location for cut

8) Plunge cut with short pecking motion to cut valve relief notch to desired depth ( used .050")

It does not look like much of a notch but the .080 valve clearance I had, Plus the .050 clear once cut should yield a toll clearance of 0.130 on the intake



HELP NEEDED:

How deep can I safely cut may valve notch before the crown is too thin?

The Keith black 96 pistons seem to measure a crown thickness of 0.220 and removing .050 gives me the minimum thickness of. 0.170

I am worried I need to take a deeper cut as the valve may have been in the mechanical notch made when the piston Kissed. Sure I will measure again and once more when the heads are done but would be nice to cut this one to depth and me to the next one