Stock Rocker Wipe Pattern Width
Thread Starter
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Stock Rocker Wipe Pattern Width
I have been going back and forth on whether to install my Crane setup (fully adjustable) or the stock rockers. I did a wipe test tonight on my stock rockers and they appear to have a fairly wide wipe pattern. Has anyone checked the wipe pattern with the stock rockers?
I don't have the heads on the car yet, but the block is ready and so are the heads. I am doing a simple mark test at valve closed and valve open and the marks indicate the rockers are wiping much wider than I can set up the adjustables.
How wide have people found their wipe pattern to be on the stock rockers?
I don't have the heads on the car yet, but the block is ready and so are the heads. I am doing a simple mark test at valve closed and valve open and the marks indicate the rockers are wiping much wider than I can set up the adjustables.
How wide have people found their wipe pattern to be on the stock rockers?
Safety Car
Joined: Sep 2003
Posts: 3,558
Likes: 2
From: Cape Coral FL
I know you've been working on this for a while. I found this link and it's a great read for info on the subject. Mid-Lift
My take on this from reading the above link, until I got a headache, is:
The distance from the rocker boss bolt center and valve tip center is fixed. The rocker arm length is also fixed. So, to get optimum wipe, and therefore optimum lift at the valve, the rocker arm tip must be exactly 90 degrees to the valve stem at mid-lift, and the rocker tip should be in the exact center of the valve stem tip at that point.
This will guarantee that the rocker will waste the least lift due to lateral motion and the valve acceleration will remain as close to constant as possible.
What I gather from this also is, all things above being equal, the more lift you have on your rocker, the wider your wipe pattern will be.
The other side of that is, the narrowest pattern you can make with your given lift is the closest you will get to accurate mid-lift geometry, also making sure the wipe pattern is centered.
The only way we have to accomplish this is to either shim or mill the rocker stud bosses.
I know you have been working to get your wipe pattern as narrow as stock, but according to the above information you shouldn't be able to. One could use the gross rocker lift and deduce the wipe using geometry to arrive at the narrowest, or ideal, wipe width, then shim or cut to get that. I think that with a cam with around .100" more gross lift than stock you would see approx. .015"-.02" wider wipe than stock.
My take on this from reading the above link, until I got a headache, is:
The distance from the rocker boss bolt center and valve tip center is fixed. The rocker arm length is also fixed. So, to get optimum wipe, and therefore optimum lift at the valve, the rocker arm tip must be exactly 90 degrees to the valve stem at mid-lift, and the rocker tip should be in the exact center of the valve stem tip at that point.
This will guarantee that the rocker will waste the least lift due to lateral motion and the valve acceleration will remain as close to constant as possible.
What I gather from this also is, all things above being equal, the more lift you have on your rocker, the wider your wipe pattern will be.
The other side of that is, the narrowest pattern you can make with your given lift is the closest you will get to accurate mid-lift geometry, also making sure the wipe pattern is centered.
The only way we have to accomplish this is to either shim or mill the rocker stud bosses.
I know you have been working to get your wipe pattern as narrow as stock, but according to the above information you shouldn't be able to. One could use the gross rocker lift and deduce the wipe using geometry to arrive at the narrowest, or ideal, wipe width, then shim or cut to get that. I think that with a cam with around .100" more gross lift than stock you would see approx. .015"-.02" wider wipe than stock.
