Mathmatical Way to figure PTV clearance??(valve relief size)
09-25-2003, 08:45 AM
#1
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Mathmatical Way to figure PTV clearance??(valve relief size) I'm going to be rebuilding my shortblock. I already know what the rod length, how much the heads are milled, and the valve sizes. I also know what the cam specs are going to be. I will definately need some valve reliefs. Is there a way I can figure out how big the valve reliefs need to be before getting my hands on the cam card with just the general specs?
Basically I'm wanting to get the parts ordered for the shortblock so I can get it together while saving for the other parts. I'm thinking of going with some JE forged pistons.
Basically I'm wanting to get the parts ordered for the shortblock so I can get it together while saving for the other parts. I'm thinking of going with some JE forged pistons.
09-25-2003, 11:14 AM
#3
Re: Mathmatical Way to figure PTV clearance??(valve relief size) I think its a yes... but its a tricky one.
THe reason I say that is that you have to keep track of the piston and the lift of the cam, in a particular lockstep way. While the piston is going to move in an 1 dimensional elliptical fasion up and down the cylinder, the edge of the valve will move along a lobe (ideally) which does not have an equation assigned to is. You could take a bunch of lift points and map an equation to it I suppose.... You would also have ot know how far the lower edge of the valve rests from TDC of the piston. That included several factors including how far into the seat the valve rests, and some trigonometry to figure out where the edge is itself.
IMHO, you would have to know so much about the system that its probably far easier to clay it up.
Sorry bout that...
chris
THe reason I say that is that you have to keep track of the piston and the lift of the cam, in a particular lockstep way. While the piston is going to move in an 1 dimensional elliptical fasion up and down the cylinder, the edge of the valve will move along a lobe (ideally) which does not have an equation assigned to is. You could take a bunch of lift points and map an equation to it I suppose.... You would also have ot know how far the lower edge of the valve rests from TDC of the piston. That included several factors including how far into the seat the valve rests, and some trigonometry to figure out where the edge is itself.
IMHO, you would have to know so much about the system that its probably far easier to clay it up.
Sorry bout that...
chris
