guillaumeber

Hello!

I have a simple question here!

Today, I wanted to check my valve lift to diagnose a problem I have and I'm suspecting the camshaft.

I removed my valve cover and put a dial indicator on the valves retainers and rotated the engine via the crankshaft bolt (sparkplugs removed). I realized that I couldn't check the valve lift that way because I have hydraulic lifters and when under pressure, they discharge slowly and my dial indicator needle drops slowly. So I can't get a good reading that way... about impossible.

The cam manufacturer of my camshaft (Comp cams) also gives the ''lobe lift'' spec, so I decided to remove the rockers and put my dial indicator directly at the tip of the pushrods. I figured that the internal pressure of the dial indicator was not strong enough to compress the hydraulic lifters and that I should get a pretty good reading. (The pressure of the dial indicator is pretty low).

I wanted your opinion if that is a proper way to check the camshaft lobes lift?
The reading i got seems pretty bad if that is the case...

Please let me know!

Have a nice day!

G.b.

MelWff

Unless you remove one of the valve springs and install a light spring your method should give you the correct lobe lift.

REELAV8R

yes that would work. You might have to push down lightly on the pushrod to get the lifter to follow the cam lobe back to the base circle.

guillaumeber

Humm, Yeah! I completly forgot to push down on the pushrods when doing the test... maybe that's the reason of my bad readings..! only 2-3 lobes on the 8 I checked were near the specs... the other were muchh lowerr!

thanks!

g.b.

jnb5101

I thought that when the lifter rises into the bore, the fill hole is closed(by contact with the bore hole) and it will not compress. The "adjustment" is when the lifter is on the base circle and the fill hole is exposed to engine oil pressure. Please correct me if I'm wrong!

guillaumeber

That seems right to my understanding too, but when I'm checking the valve lift with my dial indicator, the lifter has to be at it's bottom position at some point (on the base circle) and then the oil drips out...giving bad readings...

g.b.

Danish Shark

With the motor running, yes (dynamic scenario).
With the motor stopped, no (static scenario).
With the motor stopped the oil has time to flow through the openings created because of the tolerances needed both inside the lifter and between the lifter and the block.

REELAV8R

Oil would only run out if you had bad lifters. Otherwise oil stays in the lifter unless it's pushed out. Other wise you would have a whole lot of lifter noise on every start up until the lifters pumped up.

Listen to an 80's vintage Subaru for reference. They regularly had lifters go bad and clacked to beat he** at start and/or while idling.

guillaumeber

Maybe my lifters are all bad then ... or maybe to much play between the lifters and their bore... but my dial indicator indeed show a little drop of the lifters on the indicator... a slow leak in the lifters... but the engine did not clack or make noise... fortunatly...

thanks
g.b.

Danish Shark

With checker springs or regular valve springs?
That's normal if you have the regular valve springs in it. That way the oil is slowly pushed out of the lifters.

guillaumeber

I did using regular springs! That would explain the slow leak.

I figured that I was better of taking the reading directly on the top of the push rods instead of the valve itself to avoid buying and installing all checker springs and then back to regular springs.

thanks
g.b.

larrywalk

Yes, this method is correct and works well because there is a spring inside of hydraulic lifters which pushes the push rod cup up to the top of the hydraulic lifter. This spring is a lot stronger than the tiny spring internal to the dial indicator. As noted, just make sure that the lifter follows the lobe on its descent by applying a slight pressure downward on the push rod to make sure it's not sticking in the lifter bore.

As determined, this is only cam lobe lift (from the base circle to the peak of the lobe); valve lift will be this value times the rocker ratio when the rocker is replaced. For solid lifters, it will be times the rocker ratio less the valve lash.