Cam lobe issue?

[88bluestar]

Car was running fine after break in. Started popping and initially thought I had distributor issues but after repeated attempts to remedy it I decided to tear down to inspect the cam and lifters. What causes the lifter to get this groove, possibly not rotating in the bore? All other lifters had regular wear.

[swampbuggy]

that almost has to be what happened, IMO Mark H.

[af2]

No spin. Either cam has no taper or lifter bore seized.

[Kbails]

take better pic of the lifter maby with a flat edge on it. hard to tell in the pics

[88bluestar]

It has a thin cave in to it but it right in the center, no more than 25-30 thousands wide. Was never ran on track and never seen anything over 3500 rpm

[volodkovich]

OHC bucket followers usually spin via offset lobe to lifter centerline. That hasn't been spinning- if the bore and lifter seem fine check the offset and taper on the cam lobe.

[DaveMcLain]

It has a thin cave in to it but it right in the center, no more than 25-30 thousands wide. Was never ran on track and never seen anything over 3500 rpm

Low RPM running can cause this sort of thing to happen for a few reasons. I think what happened is simply that the cam and lifter started gaulling, transferring metal and then the game was over. After a short time the lifter can't rotate any more because of this wear.

Flat Cam

[CamKing]

There seems to be a bunch of SBC timing sets out there, where the bore in the gear that the front of the cam fits in, isn't deep enough, so the cam sits too far back in the block. That can cause all kinds of wear issues.
Pull the lifters out, and see how the lobes line up with the lifter bores. The centerline of the lobes should be slightly forward(towards the front of the block) of the centerline of the lifter bores.

[F-BIRD'88]

On the SBC the cam has to be able to "walk" forward to self find its happy spot under the lifters. It does this all by itself by the function of the crowned lifter face and tapered cam lobe. This then allows the flat tappet lifter to spin when running. Do not use a cam button on a SBC with a flat tappet cam.
Do not restrict the FLAT TAPPET cams natural for aft movement in the block.
Cam Buttons are only used on roller cams on a SBC.
Next time put a lil Moly M2SO4 in the oil and lighten up on the valve spring seat and open load to near OEM stock loads for the critical flat tappet cam break in.
The Moly (and zinc) in the oil prevent galling and metal transfer between cam and lifter face especially during break in.
Or use a oil that has some Moly and zinc in it already.
Set the initial valve lash TIGHTER than the cam card hot lash spec...especially for the inital break in.

When it is all broke in THEn change the valve springs to correct spring seat and open load spec for the job at hand. Excessive valve springs pressure ( especially during initial run in) is real hard on the new cam and lifters.


When you run increased seat and open valve spring loads ( over OEM stock spring loads) for max performance on a high perf racing flat tappet camshaft the little bit of Moly in the oil really helps reduce early cam lifter failure and extends life.
It also helps reduce wear/extend life on stuff like lifter bores, pushrod tips etc etc.

[superpursuit]

On the SBC the cam has to be able to "walk" forward to self find its happy spot under the lifters. It does this all by itself by the function of the crowned lifter face and tapered cam lobe. This then allows the flat tappet lifter to spin when running.

Actually the crowned lifter face and tapered lobe and the distributor gear all act to pull the camshaft backwards.

A little information , on what engine type this is, and clearer photos taken under better light would be helpful.
It seems people are trying to guess what engine this is.

[MadBill]

<EDIT: Written before seeing above post.>
Lobe taper, lifter radius and oil pump drag* all pull the SBC/BBC flat tappet cam rearward. (*Although it's not constant enough to totally prevent float, I've seen the front thrust surface of a BBC block chewed up shortly after a way-high oil pressure relief spring was installed.)

Also, on Chevs I have checked, the crank sprocket is offset perhaps 0.025" rearward from the cam sprocket, adding an additional rearward load due to the chain drive tension.

[user-17438]

On the SBC the cam has to be able to "walk" forward to self find its happy spot under the lifters. It does this all by itself by the function of the crowned lifter face and tapered cam lobe. This then allows the flat tappet lifter to spin when running. Do not use a cam button on a SBC with a flat tappet cam.
Do not restrict the FLAT TAPPET cams natural for aft movement in the block.
Cam Buttons are only used on roller cams on a SBC.
Next time put a lil Moly M2SO4 in the oil and lighten up on the valve spring seat and open load to near OEM stock loads for the critical flat tappet cam break in.
The Moly (and zinc) in the oil prevent galling and metal transfer between cam and lifter face especially during break in.
Or use a oil that has some Moly and zinc in it already.
Set the initial valve lash TIGHTER than the cam card hot lash spec...especially for the inital break in.

When it is all broke in THEn change the valve springs to correct spring seat and open load spec for the job at hand. Excessive valve springs pressure ( especially during initial run in) is real hard on the new cam and lifters.


When you run increased seat and open valve spring loads ( over OEM stock spring loads) for max performance on a high perf racing flat tappet camshaft the little bit of Moly in the oil really helps reduce early cam lifter failure and extends life.
It also helps reduce wear/extend life on stuff like lifter bores, pushrod tips etc etc.

I sure hope you don't build engines for a living.

[77cruiser]

On the SBC the cam has to be able to "walk" forward to self find its happy spot under the lifters. It does this all by itself by the function of the crowned lifter face and tapered cam lobe. This then allows the flat tappet lifter to spin when running. Do not use a cam button on a SBC with a flat tappet cam.
Do not restrict the FLAT TAPPET cams natural for aft movement in the block.
Cam Buttons are only used on roller cams on a SBC.
Next time put a lil Moly M2SO4 in the oil and lighten up on the valve spring seat and open load to near OEM stock loads for the critical flat tappet cam break in.
The Moly (and zinc) in the oil prevent galling and metal transfer between cam and lifter face especially during break in.
Or use a oil that has some Moly and zinc in it already.
Set the initial valve lash TIGHTER than the cam card hot lash spec...especially for the inital break in.

When it is all broke in THEn change the valve springs to correct spring seat and open load spec for the job at hand. Excessive valve springs pressure ( especially during initial run in) is real hard on the new cam and lifters.


When you run increased seat and open valve spring loads ( over OEM stock spring loads) for max performance on a high perf racing flat tappet camshaft the little bit of Moly in the oil really helps reduce early cam lifter failure and extends life.
It also helps reduce wear/extend life on stuff like lifter bores, pushrod tips etc etc.

I sure hope you don't build engines for a living.

[randy331]

On the SBC the cam has to be able to "walk" forward to self find its happy spot under the lifters. It does this all by itself by the function of the crowned lifter face and tapered cam lobe. This then allows the flat tappet lifter to spin when running. Do not use a cam button on a SBC with a flat tappet cam.
Do not restrict the FLAT TAPPET cams natural for aft movement in the block.
Cam Buttons are only used on roller cams on a SBC.
Next time put a lil Moly M2SO4 in the oil and lighten up on the valve spring seat and open load to near OEM stock loads for the critical flat tappet cam break in.
The Moly (and zinc) in the oil prevent galling and metal transfer between cam and lifter face especially during break in.
Or use a oil that has some Moly and zinc in it already.
Set the initial valve lash TIGHTER than the cam card hot lash spec...especially for the inital break in.

When it is all broke in THEn change the valve springs to correct spring seat and open load spec for the job at hand. Excessive valve springs pressure ( especially during initial run in) is real hard on the new cam and lifters.


When you run increased seat and open valve spring loads ( over OEM stock spring loads) for max performance on a high perf racing flat tappet camshaft the little bit of Moly in the oil really helps reduce early cam lifter failure and extends life.
It also helps reduce wear/extend life on stuff like lifter bores, pushrod tips etc etc.

I sure hope you don't build engines for a living.

Randy

[F-BIRD'88]

No I don't build motors for a living. I do it my self, for myself or those that ask.
Mostly to avoid mistakes made by so called pros. And I don't have problems like this poster has seen with flat tappet cams.
Along with my other cam break in advice (light/oem level springs, moly in oil etc), do not use a cam button on a flat tappet cammed SBC BBC.
Interesting about the recent cam gear machined depth.
Funny, the only issues I have ever run into are machining errors and assembly errors Like finding a cam button on a flat tappet cammed motor. Thats why I do it and check it myself. Ya it takes longer but I don't do it for money.