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

[rfinegan]

Piston set up on valve center to Centerline of Quill

[rfinegan]

Cutter and finish cut to .050 pocket

[rfinegan]

Now you too, have the information and skills to Valve notch your own pistons!

Only 3 more to go...

[PatMc]

Now you too, have the information and skills to Valve notch your own pistons!

Only 3 more to go...

...and that's why I always angle the workpiece (if at all humanly possible) and not the quill....I've made that mistake a few times.

Nicely done.

[ChrisFoley]

I made a fixture to hold pistons at the correct angle rather than reposition the quill.
While I generally wouldn't use abrasives like that on a milling machine, your process is certainly adequate to make small eyebrows. Looks good.

Did you measure the intake clearance with playdoh on one of the unaffected pistons?

I'm also curious if maybe the problem was initiated by valve guides that were too tight, and not an over-rev.

[rfinegan]

Final Clearance measured on # 1 cylinder . ( small smile fail) with dial indicator

Intake @ 10 degree first opening. 0.150 in min piston to valve clearance
Exhaust 10 degree before closing. 0.118 in min piston to valve clearance

I think that was correct ( I put tape on degree wheel as reference)THIS IS THE CLOSEST MEASUREMENT

I also pulled the swivel feet and put regular adjusters in set to Zero lash. This was to ensure the feet were not binding and increasing the lift? I will ensure the clearance to the rocker when going back together after new valves and check that the geometry is correct too

@ChrisFoley

Next:
I will measure the Clearances on # 2 cylinder ( this is a no fail Cylinder ) for a before and after comparing and notching

BTB:
1) Both rear cylinders were Intake failures
2) Both intake failures shared the same come lobe
3) Both rear cylinders get hotter? # 3 gets the hottest
4) #3 intake had the most damage and severe Valve bend (Stuck valve)
5) #1 intake kissed but opens and closes (sticks some times ) perhaps a smaller bent valve

[ChrisFoley]

How much larger is the eyebrow radius than the valve head? It should be at least a couple mm.

[rfinegan]

Radius is .050 larger.
Or added .100 to the diameter for the valve 1.832 ( 44 mm valve 1.73228)

How much larger is the eyebrow radius than the valve head? It should be at least a couple mm.

[rfinegan]

I did a valve to piston check on Cylinder 2 both intake and exhaust...


Intake piston to valve has a min clearance of 0.100 in
Exhaust piston to valve has a min clearance of 0.110 in

I wish the numbers we a perfect match for each cylinder, but I am sure the valve geometry has something to do with the Max lift.
or
The Deck height
Cylinder 1= 0.037 in
Cylinder 2= 0.040 in


The #2 intake of .100 + .050 notch relief=.150. this is the same or very close the the results above

[930cabman]

Are your valve springs up to the task?

[rfinegan]

Yep,

Brand new double spring/HD springs
retainers/keepers
New SS Valves
Seats
Guides
mild porting
cut chambers
57 cc for 9.0:1 compression at .040 deck
all the good stuff
should handle the SS 44/38 valves well above 6k

-Robert

Are your valve springs up to the task?

[rfinegan]

Raby Cam

[rfinegan]

Ha haaaa...

[930cabman]

Thanks for reporting with this good information. Conclusion: .100/.110 is not enough clearance?

[rfinegan]

@930cabman
Racer Chris comment in the past that 0.120 on intake and 0.080 on exhaust is desired. Other internet research said:There are some racers who go as low as 0.060 and others say the exhaust have to be lager clearance for thermal expansion. Who knows?

I am still not sure of the root cause here. Other than the obvious , "Kiss" of the valves to piston.

1)Over Rev? Was running good before 3k rev to set timing (Occasional Spark knock)
2)Sticking Valve: Guide to tight
3)Previous over Rev: Slight kiss to bend valve and tighten valve guide. Causing sticking valve and collision with piston ( never hit rev limiter 6500)but engine has seen over 6k on strong pull
4) Oil temp never above 240*f. Stock gauge estimate 3/8" from red (350) mark when running hard

Notching for the valve relief is EZ with engine apart. Other then a slight drop in compression and perhaps a little change in the Quench area it should have little negative impact.

I do plan on re-balancing the Pistons when I am done...

Should I also open the clearance for the Exhaust side too? With a smaller notch for the smaller exhaust valve?

Lets see where this thread takes us...

-Robert

Thanks for reporting with this good information. Conclusion: .100/.110 is not enough clearance?

[rfinegan]

One good things about grinding/sanding the valve notch is the rounded radius. No sharp edges or very few...


Within a 0.10 of a gram of each other. ( I was a little bored) and worthless till the other 2 are done!

[maf914]

rfinegan,

Thanks for posting your engine build and these latest piston valve notch details. While I understand what you are doing I have nowhere near the skill to do detail work like this, nor the equipment to do it. I really would like to see you put this thing back together and say that it is running great.

One thing I was wondering is that when you do the valve notch do you then polish the piston top and valve notch to eliminate possible sharp edges that might cause hot spot pre-ignition? That just some stuff I remember from engine build magazine articles. (IMG:style_emoticons/default/laugh.gif)

[rfinegan]

@maf914

Thank you for the encouragement. There will be a Dyno day in my future! I hope it will be before the new year.

As for the sharp edges and preignition and hot spots, you are correct. Same with the stress risers on sharp milled edges. They need to be radiuses too. I was referencing this a little as I used grinding/sanding and not a Cutter to make my notches. It is what had/could make . But it does make for softer edges. A bit harder to make things repeatable for volume depth and weight. But EZ to take a few 0.10 of a gram out for final balancing.

For those wondering how to get the depth correct on an angle quill? MATH?

I do not know either.

No DRO (digital read out) here. So I got out my feeler gages. Or more correctly Wire Spark plug gages. I selected the 0.50 wire gage and lay it flat along the milled pocket at the deepest. I guest a straight edge razor blade across the piston top to feel for it to catch. I continued to cut till the razor no longer catches on the gage. Then some sanding sticks to clean up and radius.

[rfinegan]

FROM THE WEB:

According to WebCam the minimum clearance is .050 for the intake and .080 for the exhaust.

Massive T4 says do not go below 0.080


Here is a video of cutting the Intake valve notch

https://www.youtube.com/watch?v=E99SJnPKX4k

[rfinegan]

I am not convinced my clearances were an issue. But an ounce of preventions they say....

I did find my Deck height is the following:

1) =0.037
2) =0.040
3) =0.040
4) =0.037


Each valve notch is 0.050 and is indexed off the Center line of the valve guide

Piston weight in at less than .5 gram of each other with piston pins installed
Valve to piston clearance
Was
Intake 0.100
Exhaust = 0.110

Math calculation. Old + 0.050= Total clearance

NOW:
Intake = 0.150
Exhaust = 0.160

I will measure real clearances again once the heads are repaired...

But for now....
Thank you to all that contributed and checked in on this thread (IMG:style_emoticons/default/beerchug.gif)


Best Regards

-Robert