cam is too far in? lifter is hitting another lobe

[John2037]

I am a pretty good mechanic but I have ran into more problems than I can shake a stick at with this 3.0 gm..... First machinist messed up the cut on the crank, second told me the head was good, seven valves later it was.... Now it sounded like another valve knock on #2 so I checked out the lifters (which are new) #2 intake lifter is all chewed up on the edge. Now I know the lifter isn't suppose to be dead on aligned with lobe but it is hitting what looks to be a unused lobe right next to it.

The block was inspected, cut and assembled by a shop and it idled pretty well until I tached it up then came the knock.

I have to pull the motor again but has anyone seen this? Thoughts?

 

[Don S]

Re: cam is too far in? lifter is hitting another lobe

It sounds like you may have a missing/broken thrust plate on the cam.

 

[John2037]

Re: cam is too far in? lifter is hitting another lobe

Maybe I just can't imange them forgetting that. Does that thust plate keep the cam from moving forward or backward (in a groove?)

 

[John2037]

Re: cam is too far in? lifter is hitting another lobe

I ask becausei was thinking maybe the pressed on gear was sliding out but if that plate holds both directions than it mustbe missing

 

[Don S]

Re: cam is too far in? lifter is hitting another lobe

Yes, there is only .003 to .008 clearance that the cam can move back and forth. It's possible the gear is coming off, but never heard of that happening before, and that engine has been around since the late 60's.

You're just going to have to pull it apart and look.

 

[John2037]

Re: cam is too far in? lifter is hitting another lobe

Thanks don, when I find out ill post cause I've never seen this and I'm sure not too many others have.

 

[John2037]

Re: cam is too far in? lifter is hitting another lobe



Gear is sliding off.... now to fix it... I am thinking new cam gear, maybe there was something wrong with this one?

 

[Don S]

Re: cam is too far in? lifter is hitting another lobe

A new gear would be my first thought. That one was too loose. Nothing happened to the end of the cam was there? No one sanded it smooth or something like that.

 

[John2037]

Re: cam is too far in? lifter is hitting another lobe

From what I can see I am not sure - the cam and gear were new for the installer. It was just pressed on have you ever heard of using some kind of bonding to garuntee this doesn't happen again - jbweld maybe?

 

[Don S]

Re: cam is too far in? lifter is hitting another lobe

JB-weld, not a chance. It's a press fit, anything you put on it will be pushed aside when the gear is pressed on. Have never heard of one coming apart like that before. Maybe the installer forgot the thrust plate and had to remove the gear and re-install it. That would for sure loosen things up.
Put a new gear on it and try it.