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Discussion Starter #1
I know, all things being equal, a dished valve will give up a few cc's to a flat valve
and I know dished valves are usually lighter....
... but what primarally dictates whether a dished valve or a flat valve is called for?

thx!
 

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I will give up a couple of cc's instead of a heavy ass valve. I have a couple of BBC 2.19 flat intake valves that weigh a ton.
 

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Discussion Starter #4
I like the the lighter weight for sure, but I was wondering about swirl and chamber shape and piston shape and how all that figures into the valve shape. Is there any gospel?
thx
 

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Idiot Savant
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I like the the lighter weight for sure, but I was wondering about swirl and chamber shape and piston shape and how all that figures into the valve shape. Is there any gospel?
thx
Get a hot cup of coffee. Pour some cream it it, watch the cream distribute, then do it again. Will it be the same way twice?

Rings are bouncing off the walls, cylinder aren't round any more, piston is shaped like an egg, rod is whipping like spaghetti, everything is moving at mach 6, spot temps are all over the where.

Gospel? Control the valve. The heavier it is, the harder it is to control.
 

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Discussion Starter #6
I get what you are saying, but I gotta add, last time I was in Seattle they were putting little hearts and flowers in the cream..... of every cup! lol!
That dish must have some aerodynamic effect, but maybe it's so inconsequential it doesn't matter.
thx
 

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i know some people of the belief the dish is another source is a partial dead pocket (like the valve reliefs area) where the air and fuel wont combsut as effcient as possible.
 

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A flat valve will out flow a tulip valve. Look and see how many tulip valves are used in an all out race motors, none.
Doug
 

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Let me rephrase: 90% or more of the automotive gas race engines benefit from a flat head valve. Weight isn't flow. Agreed weight is a serious issue at high RPM. Most of us mortals run 7000 rpm and lower using a stainless valve. Titanium would save more weight than a tulip valve.
Doug
 

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Discussion Starter #12
So if you take a head with flat valves that's maxed out at how-ever-many CFM, it can't flow any more, and you replace the valves with tulip valves, will the power decrease?
 

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Discussion Starter #15
waitaminit! .... less compression equates to less power, flat valves allow more flow.... and the power wouldn't change?
hows that work?
 

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some people need to read. the discussion is in regard to flat face vs dished face not nail head vs tulip valves which is a totally different question
 

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I would like to see a test where a flat valve and a dished valve are tested to see what happens to the air and mixture in the chamber. Does the dish cause more turbulence where as the flat just pushes it out and away from the head of the valve? Has there been a test done like this? Kinda like what John Kaase did with the clear intake runners?
 

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The tulip term is a little confusing in this thread...

I'm a weight savings junkie so I like hollow and under-cut stems and dished faces... :)
 

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I would like to see a test where a flat valve and a dished valve are tested to see what happens to the air and mixture in the chamber. Does the dish cause more turbulence where as the flat just pushes it out and away from the head of the valve? Has there been a test done like this? Kinda like what John Kaase did with the clear intake runners?
🤦🏿‍♂️
 
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