Camshaft question

[savage75]

I understand but the surface area of the valve matters hence oversized valves= power low mid range.... longer valves smaller surface area = power top end.

[br4inl3ss]

they're all the same unless its BIG VALVE head. 64 69 is just the lenght according to the rocker. you cannot use 64mm valve with 69mm rocker and vice versa. you can swap 64mm valve & rocker to 69mm valve & rocker and vice versa.

there is absolutly NO performance difference btween 64 and 69 because they're exactly the same. they open the same. they seal the same. they're the same size.

i repeat, 64mm IS NOT THE SIZE OF THE VALVE BUT THE LENGHT OF ITS ROD.

[sinfull]

Look at the cutaway video of the head, I don't know how to link it but it should come up when search. If I remember correctly 69mm valve has more meat and can be ported, 64 mm has a lower seat and can not be ported because of the thinness of the material, easier to blow through the port. Or the other way around, if you want performance and matched port to intake and exhaust, then go for the thicker head

[sinfull]

It is in the 49cc tech library, under 4 stroke sub category, 64mm vs 69mm, Brent already cut a head in half for us 👍

[br4inl3ss]

ok

i dont see why you are so stubborn with this nosense...

139qmb head and valve are all the damn same. no one is bigger. 69mm valve fit right in place of 64mm, and 64mm fit right in place of 69mm because they're exactly the same. IDENTICAL. not more and not less "meat".
the only difference is the LENGHT, so they can be swapped easily as long as you use the proper rocker.

if you are still stubborn with that nosense, buy both 64 and 69mm valve and compare.

i do have 4 set of valve, one from amazon one from aliexpress and the 2 other are STOCK from running engine of different generation. one had 64mm the other had 69mm. they're exactly the same but lenght. seat is the same angle is the same thickness is the same all the same.

i think you are refering to the difference between intake and exhaust valve, not 64mm vs 69mm.

[sinfull]

Brent video says different, I understand 64 and 69 are just different valve length, and both are interchangeable, my point was simply 64 length valve has a lower seat and can't be ported really, 69 length valve has a taller seat and can be ported.

Also how I tell my heads from just looking at em, valve seat down low and almost level with the deck 64mm valve, seat up high like almost at the top of the head is 69mm.

[savage75]

Hey..lol I apologize if I seem to not understand you, because I do. I'm talking about the surface of the valve PERIOD. If you have oversized valves 21.15 intake 64 or 69 mm valves their is a bigger surface area more mass for the explosion which causes more power versus a stock 64/69 mm 18/19 sized surface are valves. I also believe I do gave a true 52.4 mm valve head I have to check. If not Id like to find one or have this one ported to match like Brent's video. I'd really like to find a 4 valve. Thank you guys for your input. Let me know your thoughts.

[jackrides]

What does the size of the valve face or mass have to do with the 'explosion'?

[br4inl3ss]

watched the video 4 time again, i dont see any difference.
there is N O N E.
you are either mixing intake and exhaust valve, or didnt realize there is an optical illusion on the valve ( it SEEMS different because the "profile" on the valve top is different ( only because of different brand, not size related )

64 and 65mm are EXACTLY THE SAME but lenght. the only difference on those valve is intake vs exhaust, and brand A vs brand B.

so, last words because this is becomming a total waste of time :
64 AND 69 ARE EXACTLY THE SAME BESIDE LENGHT. IF THERE IS A DIFFERENCE, ITS INTAKE VS EXHAUST VALVE, OR BRAND A VS BRAND B.

my Glixal PoS valve look to have more meat like you say, but they're exactly the same. the top of the valve have different circle marking than my unklnown one and thats why they look different. but they're ecactly the same. all my 64mm valve weight the same, and my 2 set of 69mm that i never got to use weight the same too. orcourse intake and exhaust valve doesnt weight the same.