how deep valve notch for 4cc

[kielbasa]

Anyone know of a formula or off the top of their head how deep of valve notches are needed to get 4 maybe 6 cc. I would like to cut a 48x42 notch in a mahle 94b. .050 deep was all I needed for .689 lift but after realized I needed some more cc to stay at 10: 1. If it's easier to do 48x48 notches I guess I could do that as well. My valves are 46x40
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[flyboat]

I'm not sure but getting 4 cc from valve relief cuts in a piston will be difficult. You could try small valve reliefs plus decking the top of the piston

If you just need more cc to get the cr down, look at dished pistons.
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[mark tucker]

you could notck what is needed for clearance then mill a trough with a minor raidi about 1.75"-2" wide across the piston about 1/2" from each edge, to lower cc's more. you could do it on a test peice & then cc it and find out how much you need to cut. or work on the heads some too.try to mill in the chamber aera and not on the quench aera.idealy a reverse of the chamber shape would work great.

[modok]

You'd have to dish most of the piston a good .060"? or so to get that much

[kielbasa]

http://www.thesamba.com/vw/forum/viewtopic.php?t=498246

From this thread, it shows .160 notches gave this guy 6cc not sure how big those are but I suppose I could do 2 48mm notches start with .100 and check then go from there.

This motor had been built before heads are done by Jeff Denham and I don't want to mess with his chamber work, and don't have much left of a budget to have work done to them again. I believe they are 49cc and I counted 1cc for the tiny notches I had previously cut. I had to run geers .031 copper gaskets to get closer to 10: 1 I'm just trying to get rid of the .090+ deck.

Also motor has very few miles on it maybe 100 at most. And running total seal gapless top rings so I have a good $100 in rings. Will removing piston from cylinder screw up ring seal completely or as long as they go back in the same hole they came from it will be okay. Would quick seat stuff help anything at all?
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you don't do valve notches for CCs, you do them for piston/valve clearance. You dish pistons for CCs.
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[modok]

I guess it would depend on the pistons, most cannot go that deep

If you know the relief size and angle it is possible to figure out how many CC it is, I think a vw head is 12 degrees but I'm not really sure, do you recall?

As long as you put everything back where it came from the rings ought to stay sealed

[kielbasa]

There are several dish designs I've noticed what would be the best way. I'm going to needs to cut the valve notches another .031 deeper to keep the same clearance for taking out head gasket. I could just make everything an even .100 and figure out a small dish design afterwards. It would seem like it would only take a very small dish to get it right

Does the chamber have anything to do wish dish design? Any photos to show relation between the two?
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Ideally your dish perimeter would match the chamber on the head.
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[mark tucker]

[yamaducci]

For a point of reference here is an 8CC dish cut in Wiseco 94mm Pistons.
IIRC it is about .030" deep.



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[kielbasa]

It seems like a dish so wide in diameter would act as just adding deck. How and why does dishing benefit over excessive deck. Does that 1/4 inch ring around rhetoric deck really help?
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when you dish the edge of the piston is still tight to the head deck, for squish. When you add deck, the squish is destroyed. Not even close to the same thing.
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[yamaducci]

When you leave the edge around the piston as in my picture above you can run a zero deck to the top of the cylinder which keeps the initial combustion heat and pressure out of the cylinder and away from the sealing surface. The initial combustion force is exerted downward on the piston; as apposed to outward toward the sealing copper ring and upper cylinder. Many benefits exist but keeping the heat and pressure in the head are the main two reasons for running zero deck while maintaining a resonable compression ratio with the dish.
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Cox Racing Engines
Class 5-1600's; Stock 1600 to 2498cc Type 1's. Custom Built for you in Maryland

[catbox]

[mark tucker]

[kielbasa]

So a mirror image of chamber is best? I don't really have money or patients to d my self. I found an online calculator to figure out volume of a cylinder. 3.200" would be diameter of the dish. Then I can mess around with different depths to figure out jowls many cc other takes
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[kielbasa]

I have calculated that a .030 dish with the radius of 1.6" gives me 3.955 cc close enough to the 4cc I need. The heads are in the shop getting valve guide bosses repaired, they will be doing some welding most like so I'm sure they are doing to surface the head to make sure Its flat. So I'll wait before doing the work
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[modok]

Well, you know, since you will be doing the valve reliefs on the mill anyhow maybe you stay with your 48mm diameter and have them adjust back to say 8 degrees? or so, and flycut a valve relief shape all the way across, or at least connect the two reliefs together, that would be more slick than having both a dish AND reliefs.

CC could be calculated as a trapezoid/wedge shape 48mm by about 90mm by average depth

[kielbasa]

I could maybe do something like that. Only dish the piston to a near shape of the chamber just a bit deeper then it would be all the way around.
_________________
Gotta give my props to:
Wolfsburg Motorsports
Dubbers Toy Box
Jeff's VW Speed and Fab
4inbore.com
Kielbasa Industries