refresh my memory on how to check cam lift

[Michael F.]

I want to check the lift on my cam for wear without removing anything but valve cover...where do I check for acturate measurement. I have dial indicator and holder so do I measure at rocker or remove rocker and check at pushrod or ????? thanks guys

[Timothy B.]

Re: refresh my memory on how to check cam lift

Michael,

I will probably be corrected saying this but you will get a more accurate check by measuring valve lift in the area under the rocker cover. The problem here is rocker ratio because it's not always 1.5 to 1 so it's not accurate to convert to the lobe lift in inches.

The better area is on top of the tappet with the dial meter parallel to the axis of the tappet. You may be able to experment with the push rod end of the rocker and see what the reading is but the angle changes as the rocker lifts so measurment may not be as accurate as valve lift..

[Clem Z.]

Re: refresh my memory on how to check cam lift

do the lobe as the valve lift is all a calculation of the lobe lift times the rocker ratio. this works the best of you have the heads off. http://www.race-mart.com/items/produ...838-detail.htm

[Duke W.]

Re: refresh my memory on how to check cam lift

Remove the rocker arm and place the dial indicator tip against the pushrod. Get the indicator as close as you can to "inline" with the pushrod.

Rotate the engine until the indicator reaches it's lowest point. This is the base circle. Zero the indicator and rotate the engine until max lobe lift is achieved.

Lobe lift specs for all OE cams are in the appropriate year service manual.

Duke

[Michael F.]

Re: refresh my memory on how to check cam lift

thanks duke, will try that first, don't want to remove heads, thanks again for responses.

[Larry T.]

Re: refresh my memory on how to check cam lift

thanks duke, will try that first, don't want to remove heads, thanks again for responses.

I am going through this now and concur with Duke that the dial indicator must be in an almost perfect line with the pushrod. With the setup I was using it was not possible and by the time the pushrod was all the way up the tip of the indicator had changed position on the pushrod. I can not be sure, but I think it gave me a false reading by as much as .025. I have a new lobe checking fixture on the way that has a greater range of adjustment. Good luck.

[Duke W.]

Re: refresh my memory on how to check cam lift

The error is a function of the cosine of the angle that the indicator is off from the pushrod axis - actually the lifter axis.

If the angle is 5 degrees, the actual lift is the indicator reading divided by the cosine of 5 degrees, which is .9962, so the error is about 4 percent, which is .012" on a .3000" lobe.

If you're careful setting up the indicator, you should be well within 5 degrees.

Duke

[Larry T.]

Re: refresh my memory on how to check cam lift

The error is a function of the cosine of the angle that the indicator is off from the pushrod axis - actually the lifter axis.

If the angle is 5 degrees, the actual lift is the indicator reading divided by the cosine of 5 degrees, which is .9962, so the error is about 4 percent, which is .012" on a .3000" lobe.

If you're careful setting up the indicator, you should be well within 5 degrees.

Duke

For me it was even worse because even with the most care I could use the tip of the dial indicator could not stay engaged in the oil passage recess of the pushrod. As the pushrod moved up the tip of the indicator repositioned it self to the uppermost tip of the pushrod, above the recess of the oil passage hole where it began.

[Timothy B.]

Re: refresh my memory on how to check cam lift

I know it's more accurate at the tappet but just under the rocker cover I would try valve lift and compare to specs.