How do you mesure base circle?
#2
A little tricky.
1. You must have a known standard cam. Rotate it to the heel position and using a lifter and dial indicator -measure your inital base number. Slide the lifter out while leaving the dial in place.
2. Install suspect cam at the heel position. Install lifter under the dial indicator and check the difference.
For SBC's the usual standard base circles are .950, .900 or .875. A custom cam may have any possible number.
O
1. You must have a known standard cam. Rotate it to the heel position and using a lifter and dial indicator -measure your inital base number. Slide the lifter out while leaving the dial in place.
2. Install suspect cam at the heel position. Install lifter under the dial indicator and check the difference.
For SBC's the usual standard base circles are .950, .900 or .875. A custom cam may have any possible number.
O
#6
Originally Posted by TS1955
I thought you measure from the centerline of the cam to the heel of the lobe and multiply that by 2.
TS1955
TS1955
#7
Originally Posted by oldandtired
Now why would you want to do it the easy way????
(Great suggestion)
(Great suggestion)
Curtis
#8
Senior Member
RACING JUNKIE
Join Date: Jan 2006
Location: La.
Posts: 2,890
Doesn't make sence too me why you guys are making this so hard :shock: If the cam is installed, all you have to do is set up a 2" travel indicator (you do need to know the exact cam lift) pickup the lowest point on the cam. Then rotate the engine to the highest lift C/L. Then subtract the lowest point form the highest point, then subtract the total cam lift, you then have the base circle dia.If you don't have a 2" travel indicator use a 1" and set a 1/2" spacer under the indicator at the lowest point. If the cam is not installed, you can generally mike/measure across the C/L of the cam, since most cams donot start the lift before the halfway point on the cam (this won't be exact but will get you close enough to tell if you have a small BC cam or not) I too am a machinest for over 50yrs. and have a surface plate in my home shop and micrometers 0 to 12", plus a 1/2 doz. indicators, dial bores,Height gage, etc.
Just my 2 cents
Zip.
Just my 2 cents
Zip.
#9
Originally Posted by zipper06
Doesn't make sence too me why you guys are making this so hard :shock: If the cam is installed, all you have to do is set up a 2" travel indicator (you do need to know the exact cam lift) pickup the lowest point on the cam. Then rotate the engine to the highest lift C/L. Then subtract the lowest point form the highest point, then subtract the total cam lift, you then have the base circle dia.If you don't have a 2" travel indicator use a 1" and set a 1/2" spacer under the indicator at the lowest point. If the cam is not installed, you can generally mike/measure across the C/L of the cam, since most cams donot start the lift before the halfway point on the cam (this won't be exact but will get you close enough to tell if you have a small BC cam or not) I too am a machinest for over 50yrs. and have a surface plate in my home shop and micrometers 0 to 12", plus a 1/2 doz. indicators, dial bores,Height gage, etc.
Just my 2 cents
Zip.
Just my 2 cents
Zip.
Curtis
#10
Senior Member
RACING JUNKIE
Join Date: Jan 2006
Location: La.
Posts: 2,890
Originally Posted by doorracer
Originally Posted by zipper06
Doesn't make sence too me why you guys are making this so hard :shock: If the cam is installed, all you have to do is set up a 2" travel indicator (you do need to know the exact cam lift) pickup the lowest point on the cam. Then rotate the engine to the highest lift C/L. Then subtract the lowest point form the highest point, then subtract the total cam lift, you then have the base circle dia.If you don't have a 2" travel indicator use a 1" and set a 1/2" spacer under the indicator at the lowest point. If the cam is not installed, you can generally mike/measure across the C/L of the cam, since most cams donot start the lift before the halfway point on the cam (this won't be exact but will get you close enough to tell if you have a small BC cam or not) I too am a machinest for over 50yrs. and have a surface plate in my home shop and micrometers 0 to 12", plus a 1/2 doz. indicators, dial bores,Height gage, etc.
Just my 2 cents
Zip.
Just my 2 cents
Zip.
Curtis
Zip.
PS Curtis, CNC programming and operating CNC equipment is also what i do for a living when i work, at a plastics injection mold building com.