Short Push Rods

[60s Refugee]

How important is it to use shorter pushrods if milling a head 30 or so?

My 200 six build has resulted in noisy lifters since day one and now, after 40,000 miles it acts like I have a bad lifter. I at first thought the clatter was just from the headers, but it's more than that. I used a set of "green stripe" pushrods in my rebuild (60 short) and have since been told that the stock length would have been OK to use, and I should put those back in.

I am about to buy a new set of lifters but I need advice about the push rods.

The head was milled 30, polished, ported, big valves, hardened seats, cammed up (240 cam). Hydraulic Lifters!

Thanks

Harry

 

[rocklord]

Are you using the adjustable rockers? If not, it's difficult to get the valves adjusted right when the head is milled.

 

[JackFish]

I don't think that a .030 shave off the head warrants shorter pushrods.
I'm sure someone else may chime in with the specifics, but with non-adjustable I seem to recall you can go like over .060 at least before needing non-stock pushrods.
Did you go to a thicker head gasket too?

 

[60s Refugee]

These are hydraulic lifters, non adjustible rockers.

I used an NPD head gasket so it is whatever standard issue thickness is these days.

Harry

 

[CZLN6]

Howdy Back Harry:

THe thickness of the new head gasket is the pickle in this salad. You will need to find what brand NPD is selling so we can comput that into this equation.

For example, if you milled the head .030" and then added a FelPro head gasket at .050" you just added .020" to the pushrod length. Add to that wear on all the parts involved in the cam to valve train and you've probably exceeded the accomodation range of the lifters to accomodate. I'd switch back to the stock push rods immediately and see if that helps. If it does, you will know you are on the right track. While you have the valve cover off, be sure to check to see that oil is flowing to the front rocker within a few seconds on a cold start up. The front rockers are the last to get oil on start up and the first to show signs of wear. If needed, you may have to dissassemble and clean the rocker shaft and rocker holes to re-establish oiling to the rockers.

It is also entirely possible that you have a stuck lifter. Have you tried a high detergent oil additive? A set of adjustible rockers are sure useful- both is silencing the clatter, dealing with stuck lifters, avoiding lifter pump up and in getting the most out of a stock cam.

Adios, David