Rocker spacing

[Stangman]

curious about how everyone spaces there rockers on the shaft. Is there a spec like .025 between rocker and shims or is it just a feel thing. Theres gotta be something. I had a rocker break  once and changed just one and somehow it got tight when hot and upon tear down at the end of the year had a cam bearing worn on the opposite side of the rocker so it was like putting pressure on bearing. As some may know I have motor out and today took cam out which wouldnt come out easily and found 2 cam bearings like that. I did just get new rockers and put it all back the same way everything seamed like it had the right play but I never checked them hot. you would never know there was a problem. The first time it happened and i found the tight rocker after i got it  all back together after 500 miles I checked it to make sure it was fixed. So apparently I have the same thing happening. So I will be spacing all the rockers again from scratch but was wondering if there is a certain way to do it. If they have to much play does it bleed off oil pressure??. Alittle help please 

[dcm0123]

You add spacers under the pedestals to correct the geometry of the rocker system so the rocker arm contacts the tip of the valve in the proper location.

You change push rod length to change preload on the lifter.

I assume you are running hydraulic lifters. If you had so much preload you bottomed out the plunger (piston) in the lifters, you would have significant valve overlap and a poor idle.

If your idle is OK, I would look at other issues which could influence the amount or quality of oil at the bearings and verify the bearings were installed properly to start with.

If you are concerned you have to much preload you should buy an adjustable push rod with the same diameter balls on the tip which your engine requires. It is used to determine the proper length push rod you need.
With the cam set in the proper position you install the rod loose then increase the length so you take up all the free play but do not preload the lifter. You remove it and measure the length of the rod. Then add to the measurement the amount of lifter preload you want. Preload for conventional lifters is .030" to .040". Then you order rods of the correct length. Someone just posted NAPA sells push rods which are .03 longer or shorter than standard for $5 each.

If you measure the existing rod and someone installed the wrong length you may still have the problem even if you install a rod .03" shorter. The push rods these engines require do not have holes in them because the rockers are lubricated through the oil feed holes in the head.

The difference in preload between hot and cold should not cause a notable change in clearance/preload.

[Stangman]

Thank you but I’m talking about on the shaft you know rocker,,shim,,spacer,,rocker and so on. How much space or clearance between them

[dcm0123]

Sorry I misunderstood what you were asking.
Do you have an OEM system with springs between the rockers to keep them in position on the shaft? If so, you do not need to set the spacing.

If not then you should review what the manufacture recommends. An example from Sharp below lists the side to side clearance at .008-.012 is attached.

www.harlandsharp.com/instructions/4006BKE%20webpage.pdf

[Stangman]

That’s what I’m looking for thanks.

[gregaba]

What I find wierd is that the shims go in different locations depending on if it is a stock head or an Edelbrock head.
Greg

[fe468stroker]

I went by the recommended spacing cold and found that the gap shrunk to nothingness when hot.  Went with the .008 difference between hot and cold setting on lash (solid roller) plus their recommended gap on the rocker spacing.  Seems close now.                                       

[fairlaniac]

Make sure your shims are truly flat. Last year I was setting up my Harland Sharp rockers and would get a good dimension. Then I'd be working on others, go back and check to find they were tighter or more loose? Some of the shims were a tad wavy.

[Stangman]

If you were to leave them a little on the loose side would it bleed off oil pressure. Or that’s got nothing to do with it because of the rocker on the shaft.

[gt350hr]

   Which cam bearing position are you losing?

[Stangman]

number 2 and 3  I wish I took pictures the wear was at 3 and 9 oclock. might have had a smidge on 4. None on 1 and 5. Originally years ago it was on number 4. There was no wear at 12 and 6 oclock.

[Stangman]

this is not my cam bearing and it is not shearing like this one i just want to show the wear at 3 and 9 oclock. Mine also doesnt have any wear at 12 and 6.

[gt350hr]

  "To me" it sounds like a housing bore issue. The only time "I" have had FE bearing issues was at 6 o'clock. Usually 1,2,3 never 4 or 5. BUT this is only "my " experience.

[Stangman]

You mean cam housing, I know when there are new bushings the cam spins free. Well its at machine shop getting bearings installed so he said he will check with a cam

[cjshaker]

What I find wierd is that the shims go in different locations depending on if it is a stock head or an Edelbrock head.
Greg

Edelbrock heads use a wider valve spacing. I'm no expert on Edelbrock heads, but I thought they had 2 different spacings, depending on their '390/428' heads and the '427' heads. By "stock", they would have to mean factory 390/428 heads, and not MR, HR or TP.