Camshaft Specs?

#1

Anyone know how to check a cam for wear? Getting my head done this winter and want to make sure the cam is up to spec.

Thanks

#2

Use a fingernail gauge.

Seriously, I can get some numbers together on a stock and a performance Shrick wanna-be, Ireland “regrind” that is actually a new cam. Big differences. I have both at the ehop.

Unfortuneately for us Regional Directors, I don’t think I can measure the cam once it is installed?

How-to, anyone?

RP

#3

Some months ago I spend 3 weeks testing rocker arms and cams. I used a dial gauge and spent 4-6hrs a night measuring valve lift of different rockers, cams, and the lobes on the cams. My intent was to find out the state of wear of my cams and rockers, and to find out if one kind of rocker arm had more lift than other kinds of rockers.

What I found is that rockers from teh same mfr tend to vary, so febi rockers will vary, OEM rockers will vary and Ireland HD rockers will vary. Also, old rockers are not as good as new rockers, and my cams were all in pretty good shape.

If you are really interested in knowing the state of wear of your cams you will have to test it against a new cam. You will have to create make yourself a little fixture so you can mount your dial gauge on your head, install one cam, measure valve lift every 5deg, do it a couple more times to be sure of your #'s, then put in your worn cam and repeat.

If you are a curious soul, drive on. If you’re not, pay the $160 for a new cam and be done with it.

#4

Or have you r cam profiled by someone with a Cam Doctor or equal.

#5

[quote=“jlevie” post=69638]Or have you r cam profiled by someone with a Cam Doctor or equal.[/quote] Ya, that’s a better idea. They’ll need our cam card tho.

#6

Jim, what is the Cam Doctor?
How do we check an installed cam for big lift?

Thanks, Robert

#7

[quote=“Patton” post=69641]Jim, what is the Cam Doctor?
How do we check an installed cam for big lift?[/quote]
A Cam Doctor is a machine that measures cam shape as a function of revolution. That curve can then be compared to the known curve for a stock cam. This is the best way of telling if a cam is worn.

With the cam installed on the engine you can use a dial indicator to check how much the valve moves. And you can check cam timing the same way. I’ve been told that a stock cam is in time when the intake valve is 0.005" more open than the exhaust at valve overlap TDC. Those checks will not rule out a modified cam as the shape of the lobe can’t easily be measured.

#8

Thanks everyone…I guess I’ll have my machinest take a close look…Besides, don’t want to bump up against the new HP rule :slight_smile:

#9

Jim, you got that backwards…exhaust should be open 005" more than the intake valve at TDC overlap.

#10

Must have been a “senior moment”. I have the correct specs in my notes.

#11

A bunch of us have been trying for years to bump up against any hp rule. It’s pretty damned hard. Sure ain’t gonna happen by accident with unmolested OEM hardware.

#12

A bunch of us have been trying for years to bump up against any hp rule. It’s pretty damned hard. Sure ain’t gonna happen by accident with unmolested OEM hardware.[/quote]
I agree. I’m of the opinion that there are too many variables (and too many ways to cheat) for dyno testing to be useful for other than catching blatant cheaters.Blantant cheaters are pretty obvious on track.

Now if the dyno testing was done with an engine dyno, the results would be more meaningful.