.:HSTuners::

01-23-2003, 05:02 PM

what is a 3/4 angle valve job? what exactly do they do to your valves?

silver · 01-23-2003, 05:22 PM

it's actually a sexual position

01-23-2003, 05:23 PM

I think that a 3/4 angle valve job refers to two different types of valve jobs. i.e., a three angle valve job and a four angle valve job.

When the valves are finished during head work, the "back" of the valve(the part that's facing the stem) is "cut". the cut is made by rotating the valve (think of the valve as a wheel on an axle, and the spinning is done with the same orientation. the valve is placed at an angle while spinning and then pushed against a grinding implement. the purpose of this is to cause the air/fuel charge coming in to the cylinder to tumble and swirl. i can't answer the "why" as to how that works. anyway, depending on the angle of those cuts, and the number of different angles, there will be a different amount of swirl and tumble. i think the more of these two that there are determines a large amount of how much power a given cylinder volume will make (everything else equal)

the "3" and the "4" refer to the number of different angled faces along the portion of the valve that contacts the valve seat. it's been a long time since i had to think about this- it just occurred to me that i don't remember exactly if the valve and the valve seat are beveled (cut) or if it's just one or the other.

edit: just kidding, i searched google- the answer is that it's a treatment of the valve seat, not the valve, but the net effect is the same that i was talking about above

i took this:
The valve seat area is the most critical part of the flow path in a competition cylinder head. As you go upstream or downstream from the valve seat, the port is much less sensitive to modifications. The effect of changing the valve seat throat by just .010-inch can be greater than grinding .200-inch of material at the port entrance.
from here:
http://www.rehermorrison.com/techTalk/30.htm

i'm not sure if the way i wrote this makes sense, that is, can you visualize what i'm talking about?

01-23-2003, 05:02 PM	#1
yelizardking Posts: n/a	what is a 3/4 angle valve job? what is a 3/4 angle valve job? what exactly do they do to your valves?

01-23-2003, 05:22 PM	#2
silver Registered User Join Date: Dec 2002 Location: so cali again Age: 43 Posts: 820	it's actually a sexual position __________________ Distributor of proven performance products from top manufacturers such as: Top Secret, Ings+1, J's Racing, Varis, Amuse, ASM, GP Sports, Air Walker, Garage Defend, Kakimoto, BuddyClub, Feel's, Fujitsubo, Porterfield, KG/MM, ORC, Spoon, Mugen, and more than 200 others. If it's in a Hyper Rev, it's in our reach. http://www.bulletproofautomotive.com

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01-23-2003, 05:23 PM	#3
FasterThanLight Posts: n/a	I think that a 3/4 angle valve job refers to two different types of valve jobs. i.e., a three angle valve job and a four angle valve job. When the valves are finished during head work, the "back" of the valve(the part that's facing the stem) is "cut". the cut is made by rotating the valve (think of the valve as a wheel on an axle, and the spinning is done with the same orientation. the valve is placed at an angle while spinning and then pushed against a grinding implement. the purpose of this is to cause the air/fuel charge coming in to the cylinder to tumble and swirl. i can't answer the "why" as to how that works. anyway, depending on the angle of those cuts, and the number of different angles, there will be a different amount of swirl and tumble. i think the more of these two that there are determines a large amount of how much power a given cylinder volume will make (everything else equal) the "3" and the "4" refer to the number of different angled faces along the portion of the valve that contacts the valve seat. it's been a long time since i had to think about this- it just occurred to me that i don't remember exactly if the valve and the valve seat are beveled (cut) or if it's just one or the other. edit: just kidding, i searched google- the answer is that it's a treatment of the valve seat, not the valve, but the net effect is the same that i was talking about above i took this: The valve seat area is the most critical part of the flow path in a competition cylinder head. As you go upstream or downstream from the valve seat, the port is much less sensitive to modifications. The effect of changing the valve seat throat by just .010-inch can be greater than grinding .200-inch of material at the port entrance. from here: http://www.rehermorrison.com/techTalk/30.htm i'm not sure if the way i wrote this makes sense, that is, can you visualize what i'm talking about?