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ET: Engine (Twin) Identifying cam profiles

Paul Adams

VOC Hon. Information Officer
VOC Member
I understand the factory stamped the cam profile number on the end of the cams but this doesn't always seem to be the case. Many cams have been re-profiled and the lift spec modified. Is there an easy way to identify a cam, possibly by constructing a jig. Then where is the factory data to compare my findings against?
 

delboy

Well Known and Active Website User
VOC Member
I understand the factory stamped the cam profile number on the end of the cams but this doesn't always seem to be the case. Many cams have been re-profiled and the lift spec modified. Is there an easy way to identify a cam, possibly by constructing a jig. Then where is the factory data to compare my findings against?
I generally find Pre-War cams marked up and the Data in Richardson.
Delboy.
 

timetraveller

Well Known and Active Website User
VOC Member
The only way to be sure is to put the cams into an engine and do a valve lift graph. The Mk IIs have a rounder nose than the MK Is or IIIs but then there are 105 cams and all sorts of peoples experiments about. You can't even just measure the diameter of the base circle and the overall height of the cam to get the displacement as the lever followers give a geared up effect. Roy Robertson went to the trouble of making a mock up of the timing gear and valve lifting system so that he could measure the valve lift on his test bed and not on an engine. It was a lot of precision work.
 

delboy

Well Known and Active Website User
VOC Member
The only way to be sure is to put the cams into an engine and do a valve lift graph. The Mk IIs have a rounder nose than the MK Is or IIIs but then there are 105 cams and all sorts of peoples experiments about. You can't even just measure the diameter of the base circle and the overall height of the cam to get the displacement as the lever followers give a geared up effect. Roy Robertson went to the trouble of making a mock up of the timing gear and valve lifting system so that he could measure the valve lift on his test bed and not on an engine. It was a lot of precision work.
I was only teasing, as I was guessing this is a Post-War enquiry in the Pre-War category?
Equally of course, people have re-built Pre-War lobes.
And, as Norm' says really accurate measurement is tricky. I guess for most of us the practical way is with a dial gauge on top of the valve stem. But, then deciding what your measurements indicate what you have? Mk1, 2, 3, 105, Gary Robinson Regrind, Joe Bloggs profile. The possibilities could be endless.
cheers, Delboy
 

A_HRD

Well Known and Active Website User
VOC Member
Thanks Graham. You might like to also move the 'Norvin Carbs' thread out of the Pre-War section too. That went in there in Nov 20 I believe...
Peter
 
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