Rocker issue

[Russ85]

i have an 85 gmc with a 305. Engine started knocking yesterday and shut off. I took the valve cover off and saw that one of the rockers was lose and off of the valve. I pulled the push rod and noticed it was worn down also. The rocker next to the lose one is very lose also but all others seem to feel fine. I can obviously replace the damaged parts but I was wondering what caused it to happen. Previous owner says the guy he bought it from said the engine was rebuilt. Any ideas?
Thank you

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[Honky Kong jr]

Do you have a bore scope? You could send it down the push rod hole and have a look at the cam. May have flattened the lobes.

 

[gpmorgan]

That is a fairly common issue with that style pushrod. I always use the one piece style.

 

[74 Shortbed]

Pushrod was the cause of that, those are junk..

 

[Russ85]

Well now it seems to be more than what I thought. The new pushrod drops too far down. I must have a lifter and or cam issue as well. If it has a bad lifter any chance you think the cam would be okay?
Thanks

 

[Honky Kong jr]

Well now it seems to be more than what I thought. The new pushrod drops too far down. I must have a lifter and or cam issue as well. If it has a bad lifter any chance you think the cam would be okay?
Thanks

Pulling the intake for sure at this point is the next course of action.

 

[RustyPile]

It's possible the lifter jumped out of the bore. It might be quite a task, but see if you can get some light into the lifter area and check to see if the lifter is still in the bore.. 305's of that era were famous for their soft cams.. Couple that to the lack of ZDDP in today's oils, cam failure is not uncommon. You may have some serious work ahead of you..

 

[gpmorgan]

Well now it seems to be more than what I thought. The new pushrod drops too far down. I must have a lifter and or cam issue as well. If it has a bad lifter any chance you think the cam would be okay?
Thanks

Are you sure the cam lobe is at the top of its stroke?

 

[Russ85]

It looks like I'll have to pull the intake off and dig into it. After turning the motor over the new pushrod never contacts the rocker. It does move up and down but it's dropped too far down. I'm hoping it's the lifter and not the cam but I doubt it.

 

[gpmorgan]

Measure the lift and compare it to one of the other lobes. That should give you an idea if the cam is damaged.

 

[Honky Kong jr]

It looks like I'll have to pull the intake off and dig into it. After turning the motor over the new pushrod never contacts the rocker. It does move up and down but it's dropped too far down. I'm hoping it's the lifter and not the cam but I doubt it.

Probably collapsed the lifter. Either way the intake has to come off.

 

[Honky Kong jr]

Oh and pics are a must.

 

[RustyPile]

If that lifter has significant wear/damage on the face, it's a pretty sure bet the cam is done for also..

 

[Russ85]

Thank you for the help everyone

 

[Honky Kong jr]

Thank you for the help everyone