Reading HR cam question - HELP!

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octanejunkie

Mopar Padawan
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I am trying to "read" my new cam

Cam is a 287/298 duration with .512/.525 lift

Reading the lift at the lobe, I am getting .308 and .313 between intake exhaust and intake.

Simple math tells me
.308 x 1.6 = .492
.313 x 1.6 = .500

I read the cam installed in the block, off the lifter and off the lobe itself using a dial indicator on a magnetic base zeroed on the base circle of each lobe.

Am I reading the cam incorrectly, is my math wrong or is the cam ground wrong?
 
I would have done it the same way.
something is not right.
Who is the cam manufacturer, give them a call.

onig
 
Sounds like it's off. Intake should be .341 if it's advertised lift is based on 1.5 lifters or .312 if it's based on 1.6s.
 
If you are checking and the indicator is not in line with the lifter angle, you'll lose some reading from that angle.
 
What you can do: remove the cam, measure the diameter of the base circle. then measure the highest point of the lobe; bigger value minus smaller value = lobe lift.

Michael
 
Sounds like it's off. Intake should be .341 if it's advertised lift is based on 1.5 lifters or .312 if it's based on 1.6s.

I was expecting to see .328 on intake and .320 on exhaust to get to .525 and .512

If you are checking and the indicator is not in line with the lifter angle, you'll lose some reading from that angle.

Agreed, which is why I also read straight off the lobe

What you can do: remove the cam, measure the diameter of the base circle. then measure the highest point of the lobe; bigger value minus smaller value = lobe lift.

Michael

Pure genius Michael, I'm ashamed I didn't go there myself... genius
 
make sure your dial is at 90 or youll get deflection error also i tend to use a .500 0r .375 button on the end of the dial instead of the factory .125 ball crap it will read better and absorb indescrapancies
 
Re-read the cam per 360duster's recommendation, making sure to keep my caliper at 90 degrees to the lobe, the results were sickening actually - sending this cam back, I think the guy at the grinder was high :homework:

The cam was supposed to be .525 intake lift and .512 exhaust lift at 1.6, which by my calculations means .330 and .320 respectively at the lobe. Here is what I measured working from the front of the shaft to the rear, each lobe in it's respective position.

#1 EXH .310 x 1.6 = .496
#2 EXH .314 x 1.6 = .502
#1 INT .307 x 1.6 = .491
#2 INT .305 x 1.6 = .488
-----------------------------
#3 INT .310 x 1.6 = .496
#4 INT .307 x 1.6 = .491
#3 EXH .309 x 1.6 = .494
#4 EXH .308 x 1.6 = .493
-----------------------------
#5 EXH .312 x 1.6 = .499
#6 EXH .308 x 1.6 = .493
#5 INT .306 x 1.6 = .489
#6 INT .306 x 1.6 = .489
----------------------------
#7 INT .305 x 1.6 = .488
#8 INT .311 x 1.6 = .497
#7 EXH .312 x 1.6 = .499
#8 EXH .318 x 1.6 = .509

The bigger problem, not that this isn't bad enough, is the inconsistencies in the base circles.
#1 EXH base circle measured 1.245
#2 EXH base circle measured 1.241
#1 INT base circle measured 1.236
#2 INT base circle measured 1.240
-----------------------------
#3 INT base circle measured 1.242
#4 INT base circle measured 1.242
#3 EXH base circle measured 1.237
#4 EXH base circle measured 1.251
-----------------------------
#5 EXH base circle measured 1.238
#6 EXH base circle measured 1.251
#5 INT base circle measured 1.253
#6 INT base circle measured 1.249
----------------------------
#7 INT base circle measured 1.247
#8 INT base circle measured 1.243
#7 EXH base circle measured 1.243
#8 EXH base circle measured 1.236

With pedestal rockers, not adjustable, I would need different length pushrods for each lobe to maintain proper lifter preload/lash.

With things being this inconsistent on the lift alone, I'm afraid to look at duration - sending the cam back as soon as the call tag arrives.
 
Put the cam in the block and drop the indicator straight down through the valley. Measure it that way.

Check what you find this way against your other measurements on the same lobes.
 
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