PTV clearance #s
Thread Starter
Staging Lane
Joined: Apr 2006
Posts: 57
Likes: 4
From: Space Coast, FL
PTV clearance #s I may be over-analyzing this but it seems a little odd...checked the PTV clearance with my dial indicator and these are the numbers I came up with below...mods are in the sig..
Intake Min: .120 occurred @ 10 ATDC
Exhaust Min: .213 occurred @ 2 ATDC
The intake number sounds about right but the exhuast number seems a bit high...checked it three times as well as centerline of the cam....granted that its not a "huge" cam to begin with, but I also have Crane 1.8:1 rockers so effective lift works out to about .583 and durations @.004 are 272/280....maybe I'm just looking a gift horse in the mouth here but just want to make sure the cam is correct....any thoughts?
Intake Min: .120 occurred @ 10 ATDC
Exhaust Min: .213 occurred @ 2 ATDC
The intake number sounds about right but the exhuast number seems a bit high...checked it three times as well as centerline of the cam....granted that its not a "huge" cam to begin with, but I also have Crane 1.8:1 rockers so effective lift works out to about .583 and durations @.004 are 272/280....maybe I'm just looking a gift horse in the mouth here but just want to make sure the cam is correct....any thoughts?
I think that exhaust # is larger than stock isn't it?
Are you sure you measured on the right part of the cycle? If you measured at anything other than the "overlap" period, then that number will be bigger. This is when you see the exhaust valve open, and then close. After it closes and the intake starts to open, this is the area you need to take your measurements. This is called the "overlap period". At no other point in the four stroke cycle does the valve get closer to the piston.
Are you sure you measured on the right part of the cycle? If you measured at anything other than the "overlap" period, then that number will be bigger. This is when you see the exhaust valve open, and then close. After it closes and the intake starts to open, this is the area you need to take your measurements. This is called the "overlap period". At no other point in the four stroke cycle does the valve get closer to the piston.
Thread Starter
Staging Lane
Joined: Apr 2006
Posts: 57
Likes: 4
From: Space Coast, FL
Yeah...I'm definitely in the overlap period...checked it once again a couple more times....besides, if it wasn't in overlap I would think the intake number would be higher too since it is farther from the piston as well....
My supposition is that on the Vinci cam the overlap is a little longer than most (52 degrees vs. 40ish on most other grinds) and so the piston is just that much further on its way down before the valve opens....my best guess anyway...doesn't seem like a bad thing...just thinking outloud....anyone else have any thoughts?
My supposition is that on the Vinci cam the overlap is a little longer than most (52 degrees vs. 40ish on most other grinds) and so the piston is just that much further on its way down before the valve opens....my best guess anyway...doesn't seem like a bad thing...just thinking outloud....anyone else have any thoughts?
