Hi Guys , these are in my new 427 chevy, I know it’s guide plate wear but why ? On big block chevys the pushrods do rub the guides but not to this extent, I now have metal in the top of the head from a 30 second start up. Anyone have any ideas about how to correct this ? Thanks

 

You have to adjust the pushrod guides to have .005 min clearance by tapping them before Torquing down the studs into the heads. I've had to use a dremel to grind out the guides slots on some. There are lots of online videos of how to do it.

You do NOT want any friction!

 

Pushrods are too short.

 

I wondered about the ware up by the taper.

 

Definitely way too short and possibly not hardened as they should be. But that is secondary to the length issue.

JIM

 

Different pushrod diameters require different slot widths. My first guess was the slots are too tight for the diameter of the pushrod.

The way those are designed I would be shocked if they were not hardened.

 

Looks to me you have some geometry issues going on.
As Straub mentioned longer pushrods would probably fix it. But from your pic they would have to be a "lot longer".

Your pushrods are wearing from red arrow to red arrow. And the pushrod is tapering to a smaller diameter at the same time. Not good. They will wobble to the "left" when the valve is closed on the small diameter section. And then press strongly on the guide causing wear when opening the valve, while everything is under "load". If you look at your guide pic their wear pattern is actually tapered also.

Here is my BB from this past week:

My pushrods retain their standard diameter thru the .625 valve lift and do not taper until the very end. The above pic is at valve closed, and the blue lines indicate the pushrod wear marks as the valve opens. All wear is within the guide area.

If your lift is roughly 1/2" then your pushrods appear to have taper section that is at least 1" long. That is just too much. The taper section on mine is only about a 1/2" long. I would buy new / different pushrods that have a shorter taper section. The paralllel pushrod section of the pushrods must be inside the guideplates at both valve closed and at valve open.

Whether or not you need / want longer pushrods, well that is a whole 'nother question, and depends on your valvetrain geometry. You may need longer ones as well. I know that mine are bordering on "too short" but at least they "work".

As long as your tapered section is, your pushrods would have to be .300 or .400" longer to clear the guides properly. Is that even an option with your rocker arm geometry.

I was working on valvetrain geometry this past week, and actually had a similar problem, when my "checking" pushrod (right side above) actually hung up on the guide due to the "step" it has at the end. At least it wasn't running. Crisis averted.

What diameter are yours? Mine are Jesel and 3/8"