International Lancia Forums

I'm working on a spare engine to eventually put in my zagato and found the rockers showing wear on the cam contact areas. These rockers are original HF which means polished and shotpeened so I wish to keep them. Does anyone know if this contact area is hard chromed or if some hard material is welded on it so I can estimate the sense in trying to repair it. Rechroming is not such a problem but grinding the radius afterwards might be. Also after welding grinding is necessairy so this will be the biggest issue.
Suggestions are appreciated.
Thanks

There is a layer of hard material on the shoe. I don't know what it is. Today one would probably put stellite on. It must be something similar. If you look at the side you can guess what the thickness is (hoping the thickness is constant). The ones I have seen (many) had a very thick layer. Usually it is possible to re-grind them at least once often twice and still have enough hard material.

Yes, I have done this with success.

The wear could be due to a variety of factors; I would suspect infrequent oil changes and/or poor quality oil.

By the way,. the original HF rockers I have seen were indeed polished, but not shot-peened.

I lightened a set for myself and had them peened afterwards; the finish is very different. Valve springs are always shot peened and are a good example.

Paul

Who is able to regrind them since there is a specific radius to follow. If the radius is not according spec the cam graph is altered.

I have made a tool but the engine shop should be able to do it with their standard equipment.

Grinding them also alters the lift graph some digits after the decimal point. So does grinding the camshaft, the shape of the tip of the adjust screw, the recession of the seat, the length of the valve stem. That is life. Don't loose any sleep over it.

I seem to remember that some years ago they tested a 100 or so brand new Mercedes Benz cars which came out of production, same type, same spec. I think not even two were exactly equal in performance. It just depends how accurate your measuring equipment is.

Yes it doesn't do to worry too much - or as Huib says to lose sleep...

And who knows? Based on the Mercedes-Benz tests that Huib mentions, it might even be better!

Paul

Some theorie springs to mind. Could you positively alter the cam graph by just altering the radius of the rocker? If you make the radius smaller, lift will increase. I'm not sure how duration can be affected though...

I think the best way to find out is to grind a few old rockers and set up a cam in a spare head with a degree wheel (protractor) and a dial gauge and measure the results.

I think that the geometry otherwise would be a nightmare!

Paul

My machinist whom I spoke to just an hour ago said that grinding the rockers following the original radius is not a problem since his tool follows the contour of the undamaged part. To change the radius is a different matter and would be costly. So costly in fact that for the price of grinding 8 rockers you could almost buy new camsshafts.
But I still like the idea to modify timing with rockers only. But further brainstorming shows that enlarging the radius enlarges duration but not lift and a smaller radius might enlarge lift but shortens duration.

What I like in any technology is the seperation of functions. The designers of the Fulvia went very far in seperating functions and optimizing each one. The point also came up in the discussion about springs and shocks. Thus the cams for lift graph. The shoes for following the cams.