Camshaft core shift

[threewood]

On a flat tappet cam the lobes are tapered and the lifters are wider than the lobe. If the core shift is bad enough the lifter will jump or drop everytime it is rotated and crosses the place were the core shift is. I have seen the lifter drop .002” whenever it crosses the seem on a cam that had terrible core shift. I sent it back, the cam was junk.

This shift is more left and right. The lobe grinds look good. All lifters rotated in the bores. I'm almost thinking I could grind down that seam to get it to work lol.

 

[beebest]

Thanks for posting this. I have a new cam coming from Crower, hopefully by end of the month. I'll be looking at it more closely now. I think I'd just grind the casting flash, especially if turn around time is long. I ordered my cam back in March.

 

[threewood]

Thanks for posting this. I have a new cam coming from Crower, hopefully by end of the month. I'll be looking at it more closely now. I think I'd just grind the casting flash, especially if turn around time is long. I ordered my cam back in March.

I'm in the same camp. Minimum 2 week turnaround time for a replacement cam, at best. I'm not touching the lobe faces if I remove the parting line seam.

The rest are good and do not hit any adjacent lifters. Check every lifter for rotation while spinning the cam by hand.

 

[R/T Boy 67]

Good catch, that could have turned out nasty if you hadn't noticed it.

 

[padam]

I too am thankful for the original post.

I’m still putting my engine together, and I remember seeing slight core shift on my new comp cam. The lobes looked like they were machined correctly so I didn’t think anymore of it.

But since your post I decided to take another look. I have one lobe that’s kind of close, but no interference.

I wonder if there is a huge tolerance on the lifter bore locations or it’s the camshafts?

 

[33 IMP]

If you can make it clear with a little grinder work, I would do that. But it looks like the lobe positioning of the core (front to back) is the problem. I'd be concerned about the corresponding location of the lifter on that lobe, if the lobe taper and lifter radius are compatible.

 

[padam]

In contrast to the junk we are dealing with here;
I was dropping my flywheel off at the machine shop last week.
They showed me a roller cam they were going to install. I didn’t find out what it was for, but it was obviously made from a billet. It was drilled through the center, and all of the bearing journals were undercut to save weight. It was really nice looking. Pretty sure it was a Comp too.
I should have asked the price but didn’t.

 

[Rusty knuckles]

Give me a few for the pictures. All other lobes, no issues. The lobe pictured and circled rubs on the adjacent lifter enough to bump the cam and sprocket off the machined sprocket face.

I tried two sprockets, the old one and new one. No difference. This is spinning by hand holding the sprocket into the block.
View attachment 1846612View attachment 1846613

At first I thought you were being dramatic about a rough parting line in the casting. But wow! I'm shocked.

 

[padam]

If you can make it clear with a little grinder work, I would do that. But it looks like the lobe positioning of the core (front to back) is the problem. I'd be concerned about the corresponding location of the lifter on that lobe, if the lobe taper and lifter radius are compatible.

If you do clearance it yourself, make sure to blend it well with the base circle, with a nice radius. You don’t want to create a weak spot.

 

[threewood]

At first I thought you were being dramatic about a rough parting line in the casting. But wow! I'm shocked.

I just needed to make sure I wasn't going crazy lol. I cleaned up the parting line and was degreeing it in when I banged my head open on the garage door. Had to get 6 staples in my scalp. Blood sweat and tears have been shed ha ha.

 

[eldubb440]

I just needed to make sure I wasn't going crazy lol. I cleaned up the parting line and was degreeing it in when I banged my head open on the garage door. Had to get 6 staples in my scalp. Blood sweat and tears have been shed ha ha.

we have a thread for that

busted knuckle pictures

 

[Cranky]

I just needed to make sure I wasn't going crazy lol. I cleaned up the parting line and was degreeing it in when I banged my head open on the garage door. Had to get 6 staples in my scalp. Blood sweat and tears have been shed ha ha.

I've built a few engines over the years and never seen that kind of shift with a cam and have never seen a lifter that far off the lobe. Haven't built one in long time now but remember things were just starting to get bad.....looks like you gotta inspect EVERYTHING these days. Being a machinist taught me a lot over the years but I'm still somewhat surprised at what I'm still learning.

 

[dodgeboy440]

I've built a few engines over the years and never seen that kind of shift with a cam and have never seen a lifter that far off the lobe. Haven't built one in long time now but remember things were just starting to get bad.....looks like you gotta inspect EVERYTHING these days. Being a machinist taught me a lot over the years but I'm still somewhat surprised at what I'm still learning.

In over 50 years of messing with Mopars

I’ve NEVER SEEN Anything Like That !

Can’t say a manufacturer defect can’t

Happen but ….Its Very Uncommon

It Almost Seems Like it Could Gave Been

Mis Identified? Wrong Spec ? Incorrect
Application?? OR A Deliberate Scheme Concocted To Slander The Reputation
Of Someone Heretofore Unidentified……..

It’s The Internet You Know …..

Troll Territory I’ve Heard ….

All Sherlock’s Chime Away !

 

[padam]

In over 50 years of messing with Mopars

I’ve NEVER SEEN Anything Like That !

Can’t say a manufacturer defect can’t

Happen but ….Its Very Uncommon

It Almost Seems Like it Could Gave Been

Mis Identified? Wrong Spec ? Incorrect
Application?? OR A Deliberate Scheme Concocted To Slander The Reputation
Of Someone Heretofore Unidentified……..

It’s The Internet You Know …..

Troll Territory I’ve Heard ….

All Sherlock’s Chime Away !

I’ve got a cam from the same caster that has a similar shift.
I’m guessing my base circle is bigger (less lift) so it’s not affecting it as much.

 

[threewood]

we have a thread for that

busted knuckle pictures

 

[threewood]

I got the cam degreed. Within 1° of installed centerline so I'm calling it good. Time to clean the gasket surfaces up, install lifters for placement and spin, again. I'll take pictures of my lobe blending when I pull it out again.

 

[padam]

View attachment 1846941

Da da da da ta dant dang daaaa

 

[BSB67]

……..But it looks like the lobe positioning of the core (front to back) is the problem. I'd be concerned about the corresponding location of the lifter on that lobe, if the lobe taper and lifter radius are compatible.

I agree with this comment based on the picture in post #18. The cam-lifter interface is a complicated balance of taper, radius and contact location. Fast rate cams make this balance more critical. It seems to me that having a lobe improperly offset from the lifter could be a problem.

I would send the pictures to a third party professional on this one and get their opinion.

 

[dvw]

Most if not all flat tappet cores in the U.S. come from here, regardless of the grinder. Cores | Camshaft Machine Company
Doug

 

[Cranky]

View attachment 1846941

Ouch! The older I get, the more careful I become! Seems like even minor injuries take longer to heal....