How much can one take off the base circle without needing lash caps?
05-05-2009, 02:54 PM
#1
Nordschleife Master
Thread Starter
How much can one take off the base circle without needing lash caps?
Here's a question about 32v engines. I spent my lunch break searching but couldn't find the answer, just this question posed before in different forms. I am probably just bad at searching, if the answer is in the archives I apologize.
So I figured I'll ask this here:
How much can one grind off the base circle of the cam without having to use lash caps for S3, S4, GT, and GTS cams? Assume hydraulic lifters, either stock or the VW lifters. Is the base circle and its distance from the cam center exactly the same for all four models?
So I figured I'll ask this here:
How much can one grind off the base circle of the cam without having to use lash caps for S3, S4, GT, and GTS cams? Assume hydraulic lifters, either stock or the VW lifters. Is the base circle and its distance from the cam center exactly the same for all four models?
05-05-2009, 06:03 PM
#2
Three Wheelin'
Here's a question about 32v engines. I spent my lunch break searching but couldn't find the answer, just this question posed before in different forms. I am probably just bad at searching, if the answer is in the archives I apologize.
So I figured I'll ask this here:
How much can one grind off the base circle of the cam without having to use lash caps for S3, S4, GT, and GTS cams? Assume hydraulic lifters, either stock or the VW lifters. Is the base circle and its distance from the cam center exactly the same for all four models?
So I figured I'll ask this here:
How much can one grind off the base circle of the cam without having to use lash caps for S3, S4, GT, and GTS cams? Assume hydraulic lifters, either stock or the VW lifters. Is the base circle and its distance from the cam center exactly the same for all four models?
05-05-2009, 06:14 PM
#3
Nordschleife Master
Thread Starter
Louie, Sterling -- Thanks to both of you. This helps with planning.
EDIT: Follow up question: Take 1mm off the diameter or the radius?
EDIT: Follow up question: Take 1mm off the diameter or the radius?
Last edited by ptuomov; 05-05-2009 at 07:31 PM. Reason: Overall confusion
05-05-2009, 06:41 PM
#4
Three Wheelin'
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Remember if you reduce the base circle 1mm you only increase lift .5mm
If the stock lifters can handle the extra 1mm of travel with out lash caps, you can reduce base circle 2mm. The issue is less the lifters and more the oiling hole for the lifters. You can get a little more lift by creeating a "Channel" on the lifter leading to the hole. Not something for a dremmel, but maybe your machine shop can handle it.
If the stock lifters can handle the extra 1mm of travel with out lash caps, you can reduce base circle 2mm. The issue is less the lifters and more the oiling hole for the lifters. You can get a little more lift by creeating a "Channel" on the lifter leading to the hole. Not something for a dremmel, but maybe your machine shop can handle it.
05-05-2009, 06:56 PM
#6
Rennlist Member
I thought when they were talking reducing the base circle, they were talking about taking 1mm off the one side. so, base circle reduction is off the full diameter?
Remember if you reduce the base circle 1mm you only increase lift .5mm
If the stock lifters can handle the extra 1mm of travel with out lash caps, you can reduce base circle 2mm. The issue is less the lifters and more the oiling hole for the lifters. You can get a little more lift by creeating a "Channel" on the lifter leading to the hole. Not something for a dremmel, but maybe your machine shop can handle it.
If the stock lifters can handle the extra 1mm of travel with out lash caps, you can reduce base circle 2mm. The issue is less the lifters and more the oiling hole for the lifters. You can get a little more lift by creeating a "Channel" on the lifter leading to the hole. Not something for a dremmel, but maybe your machine shop can handle it.
05-05-2009, 07:01 PM
#7
Three Wheelin'
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Right. Base circle is the circle created using the distance from the lowest edge to the center rotating point of the cam. If you reduce the lowest edge by 1mm, you have reduced the radius 1mm. The diameter of the base circle is now 2mm less.
However taking 1 MM of the lowest edge will add 1mm to the lift. That's what most people are thinking. But if you ask a cam guy to grind 1mm off the base circle you'll only get half of what you want. Best bet is to let them know the current lift and then what lift you want to achieve. Let them figure out the math.
On my extra S cams I had Delta take off 1mm form the lower edge (2mm Base Circle reduction) for a 0.513 Lift. $200 well spent. Not as nice as a true weld and grind as base circle reduction also changes duration and lift rates. Cams are going in this weekend. We'll see fi the G-Tech and my butt dyno can tell the difference over the JME cams.
However taking 1 MM of the lowest edge will add 1mm to the lift. That's what most people are thinking. But if you ask a cam guy to grind 1mm off the base circle you'll only get half of what you want. Best bet is to let them know the current lift and then what lift you want to achieve. Let them figure out the math.
On my extra S cams I had Delta take off 1mm form the lower edge (2mm Base Circle reduction) for a 0.513 Lift. $200 well spent. Not as nice as a true weld and grind as base circle reduction also changes duration and lift rates. Cams are going in this weekend. We'll see fi the G-Tech and my butt dyno can tell the difference over the JME cams.
