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Measuring cams

848 Views 15 Replies 5 Participants Last post by  DDG
Can I use a digital caliper to measure the lobes of the cams?
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How? I've never had to b4 so I'm a little list. What/were do I measure from?
Lil I just watched that vid & used that guid to measure. I still must b doing it wrong.
Ronald G Wainwright+ said:
Lil I just watched that vid & used that guid to measure. I still must b doing it wrong.
Measure the "base circle" and then measure the base and the lobe, subtract that from the 1 measurement (base circle) and that will give you total lift.
There is a fudge factor in that solid tappets have "lash" or a small amount of play and I assume hydraulic tappets do as well, this means the valve will never see that much lift....
This has a greater affect on duration which is usually measured @ .050" of lift.
Someone with more experience can elaborate on this topic....

PS. this also assumes your valvetrain is not using rockers with more than a "1:1" ratio....
Do I measure in inches or mm?
Ok, did the measurements & came up with .349'ish lift.... That sound rite?
Well, if you said what cam/engine you were measuring that might help to tell if you measured it correctly.

Factory Audi cams are usually in the 8-10.5mm range, which is 0.315-0.413".
Whoop, 7A
7A exhaust - 10.5mm/0.413"
7A intake - 9.6mm/0.378"
varia said:" onclick=";return false;
Something's wrong with Cuatrokoop's spread sheet, some of the calculations are incorrect:

Intake/Exh Overlap: 7A, if the exhaust closes @ 3deg before TDC and the intake opens @ 6deg before TDC, then there's only 3 deg of overlap, not 12

Intake/Exh Overlap: 3B if the exhaust closes @ 9deg before TDC and the intake opens @ 3deg before TDC, then there is no overlap, there's actualy 6 deg of gap!! not 21 deg of overlap.

This also reinforced by that fact that several of the 034 guys have stated that you don't want allot of overlap (or none at all) on a turbo engine, opening the intake too early while the exhaust is still evacuating will reduce exhaust pressure and effect turbo efficiency.
Correct me if I'm wrong guys, am I way off base on this??
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