Silly question about cam lobes and lifters

[2012ChargerBlacktop]

Here it is: where should the lifter on a hydraulic flat tappet cam sit on the lobe? Does it rest dead center of the lobe or toward the timing chain side of the lobe?
I ask this because of what I’m seeing on my car which is the lifter only riding on the front half of the cam lobe as the engine is rotated. Using a pry bar(gently), when the engine is at rest, I can move the cam toward the front of the block about half the width of the cam lobe at which point the lifter is centered on the lobe.
I understand that the lobes are ground so as to cause the lifters to rotate in the bore and that there is some “walking” allowed to make this lifter rotation happen. I called the cam manufacturer to discuss this issue and was assured that this was normal for the above reason. I just would like a second opinion because I can’t wrap my head around the idea that that much cam movement is normal. This is the first classic mopar engine that I’ve ever worked on so I’ve got zippo experience. Thanks in advance!

 

[2012ChargerBlacktop]

It’s a 400 big block, necessary info right?! Lol!

 

[bm02tj]

You want the lifter outside edge to be close to the edge of the lob so it spins the lifter more efficiently
if the lifter stops spinning the cam will fail

 

[Kern Dog]

All cam lobes on NON roller engines have a taper to them. This taper does two things: It encourages the lifters to rotate and it tries to keep the cam from walking.

 

[gkent]

When you install the front timing sprocket it will position the cam properly (I'm thinking you should check that the sprocket has properly fit over the cam snout and isn't misalligned and pushing the cam too far into the block). The lobes are ground with a taper - the purpose of which is to rotate the lifter during operation. The taper is also ground on the front side of the lobe which makes the lifter put slight rearward pressure on the cam - thus negating the need for a cam button. The lifters also have their faces ground with an ever so slight curve.

So to answer your question the lifter should still be pretty close to centered on the lobe. And moving the cam with a prybar is proving nothing.

 

[Mike67]

Think about it this way if the lifter sat perfectly centered on the lobe how would it rotate? It wouldn't, it would ride on the crown of the lobe, the slight offset & taper allows the lobe to spin it much like spinning a basketball on your finger. You don't spin the very bottom of the ball, you swipe the lower 1/3.
It doesn't lift the ball it basically gives it an axis to spin on...

 

[gkent]

Think about it this way if the lifter sat perfectly centered on the lobe how would it rotate? It wouldn't, it would ride on the crown of the lobe,

No, it would rotate just fine. The cam has a taper - no crown. The taper ensures it only contacts one side of the lifter

 

[Mike67]

No, it would rotate just fine. The cam has a taper - no crown. The taper ensures it only contacts one side of the lifterView attachment 631385

You don't understand what I was trying to describe, he asked about sitting dead center on the lobe which technically can't happen.
Nice doodle though...works with the basketball comparison.
Scroll down to Lesson 5
http://garage.grumpysperformance.com/index.php?threads/camshafts-8-lessons.5154/

 

[cryplydog]

Do to dimensonal runouts of all parts you can tap or swage in the rear welch plug to adjust any glaring misalignment of the lifter/cam face.

 

[bm02tj]

The cam location is set by the thrust on the cam gear with the lifters pushing the cam back
you can not use cam plug to push forward

 

[miller]

So how about telling us, if your engine is a SB, or BB...makes a difference.

 

[miller]

It’s a 400 big block, necessary info right?! Lol!

Ah, skipped right over that. Rear surface of the cam gear sets end play. If you have that much play in the cam, need to look at your timing chain, for slack. Sounds like the chain is too loose! (Probably one of those plastic thingys.)

 

[BSB67]

Here it is: where should the lifter on a hydraulic flat tappet cam sit on the lobe? Does it rest dead center of the lobe or toward the timing chain side of the lobe?
I ask this because of what I’m seeing on my car which is the lifter only riding on the front half of the cam lobe as the engine is rotated. Using a pry bar(gently), when the engine is at rest, I can move the cam toward the front of the block about half the width of the cam lobe at which point the lifter is centered on the lobe.
I understand that the lobes are ground so as to cause the lifters to rotate in the bore and that there is some “walking” allowed to make this lifter rotation happen. I called the cam manufacturer to discuss this issue and was assured that this was normal for the above reason. I just would like a second opinion because I can’t wrap my head around the idea that that much cam movement is normal. This is the first classic mopar engine that I’ve ever worked on so I’ve got zippo experience. Thanks in advance!

You're fine.

 

[miller]

You're fine.

Don't think so...not with that much movement on the cam.

A 400 is still a BB, meaning the distributor is up front, with the dist/oil pump drive gear. That drive gear meshes with the cam, so that itself limits fore/aft cam movement. Main thing is the cam (chain) drive gear, the rear face fixes rearward movement of the cam.
If I remember right, like on the 400s, could have nylon teeth on that gear. Should be something to look at. If parts and pieces are right, the cam lobes would be centered at the lifter bores.

 

[wyrmrider]

you can move the cam a long way forward but none back which is what counts
everyone's correct
the taper puts the point of contact off center even if the lifter was centered but most I've seen have the lifter offset on the cam lobe
remember the Hemi and Six pack came with less taper and less radius on special no longer available lifters
We tried grinding cams with less taper and refinishing the lifters- which are sometimes terrible finish or have chamfers
did not seem to make much difference