Valve cover fitment

lumbee

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Put the valve cover on a fresh engine rebuilt this weekend and after tightening down the heads bolts (not torquing) I noticed the right side intake rocker would no longer freely move (though I could still turn the engine over). I pulled the valve cover off and after greater inspection noticed this raised area on the head. There is not a corresponding area on the valve cover that matches up with this. It almost looks like a washer is on there, but it's not, it's machined into the head. I think what is happening is that when I tighten down the valve cover, that the mismatch is causing the head to warp which is stoping the rocker arm from moving. I got this motor as a basket case, so it's possible these are not matching heads/valve covers. Anyone see this before, or know what year this head is from based on this raised area around the bolt hole?

Thanks in advance!

upload_2021-12-6_7-59-30.png
 

RustiePyles

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Are the valve cover/head a matched pair? They are line bored at the factory to matched pairs, they should have same numbers tamped on them. They're not really interchangeable, a rocker box from one head will not fit another head it was not originally mated with.
 

kshansen

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Are the valve cover/head a matched pair? They are line bored at the factory to matched pairs, they should have same numbers tamped on them. They're not really interchangeable, a rocker box from one head will not fit another head it was not originally mated with.

As Rusty says check for the matching numbers. They are located at the front of the head/cam cover right behind where the oil line goes up the front of engine. I removed oil line from engine on bench to get this picture of one of my engines:
head cam cover.JPG


I notice many time heads for these engine will be offered for sale on Ebay or such with the cam cover not included. Apparently by someone who has no real understanding of what they are selling!
 

kshansen

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I suppose in a perfect world they should be able to be swapped around but if say the one head or cam cover was the last one machined before the cutter was replaced or made on the next line over there could be a slight difference between the two.

I'd say if you had two of each that came off the machining line next to each other they would be close enough to work without a problem. But if one was made on Monday and the other on Friday all bets are off!

I recall one of the first diesel engines I worked on back in the 1970's. As we were getting ready to pull the crank we noticed that the numbers on the main bearing caps were out of order. Something like 1 2 3 5 4 6 7. To be safe we asked the boss what to do about this. His answer was more or less "If the engine ran that way for a few thousand hours and there was no real problem with the bearings just note the order they are in and put it back that way!" So that's what we did and that motor ran for years with no problems!
 

lumbee

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...crap shoots are part of the fun right? If it were not for the obvious issue with the tappet being stuff I'd run it. The image in my initial post seems to indicate an intentionally machined area...not just a "mismatch" of a horizontal cut.
 

gggGary

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Put the valve cover on a fresh engine rebuilt this weekend and after tightening down the heads bolts (not torquing) I noticed the right side intake rocker would no longer freely move (though I could still turn the engine over). I pulled the valve cover off and after greater inspection noticed this raised area on the head. There is not a corresponding area on the valve cover that matches up with this. It almost looks like a washer is on there, but it's not, it's machined into the head. I think what is happening is that when I tighten down the valve cover, that the mismatch is causing the head to warp which is stoping the rocker arm from moving. I got this motor as a basket case, so it's possible these are not matching heads/valve covers. Anyone see this before, or know what year this head is from based on this raised area around the bolt hole?

Thanks in advance!

View attachment 202772
You know that with the cam on, at least one valve is ALWAYS open on the 650 motor? there is valve overlap and at TDC on the non firing side both valves are open. Correct me here but "you cannot loosen the adjusters enough to have all 4 rockers free at the same time".
 

lumbee

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You know that with the cam on, at least one valve is ALWAYS open on the 650 motor? there is valve overlap and at TDC on the non firing side both valves are open. Correct me here but "you cannot loosen the adjusters enough to have all 4 rockers free at the same time".

Correct...I rotated the engine so the rocker in question was not resting on a cam lobe.
 

kshansen

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I'm assuming you tried backing off the adjuster some on the valve in question? Is there any clearance between the rocker and the valve stem?

Was this head assembled on this "basket case" motor? While you have the cover off can you try to measure the height of the valves to see if the one you are having a problem with is noticeably taller than the others? Or have you checked to see if there is a difference in the rocker arms or adjusters? Not sure if different years used different rockers or adjusters.

Just tossing out random thoughts of what could be the problem.
 

lumbee

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I'm assuming you tried backing off the adjuster some on the valve in question? Is there any clearance between the rocker and the valve stem?

Was this head assembled on this "basket case" motor? While you have the cover off can you try to measure the height of the valves to see if the one you are having a problem with is noticeably taller than the others? Or have you checked to see if there is a difference in the rocker arms or adjusters? Not sure if different years used different rockers or adjusters.

Just tossing out random thoughts of what could be the problem.

Correct...all basket case parts. Rockers all moved freely (if engine/cam rotated so rocker not on a lobe) with bolts semi-tight, but after putting a bit more torque on them (maybe 50%) then the one rocker locks up. Inspected both the head/valves and the cover/rockers and nothing seems out of place.
 

gggGary

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Only one in place in this photo, but two diagonal head studs holes have (had) locator sleeves to positively align head and cover.
cylinder head rocker cover.JPG
 

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  • cylinder head rocker cover.JPG
    cylinder head rocker cover.JPG
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Jan_P

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Thinking out loud
I have no reason to doubt Mr Pyles statement that they are machined as a pair
But if I recall right there is a like a plane surface that I feel is machined in one setting.( Milled or Ground usually )
# 11
But usually the surface is machined ( Milled ) Without shifting the part clamping just because the surface shall be plane

Something sticking out I feel is not Normal
Is it plane otherwise and are the locator sleeves all the way in moving " Freely "
Putting it out here .. ?? what happens if you file the protrusion away

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lumbee

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Thinking out loud
Something sticking out I feel is not Normal
Is it plane otherwise and are the locator sleeves all the way in moving " Freely "
Putting it out here .. ?? what happens if you file the protrusion away

View attachment 202778

..yep, flat otherwise, I suspect if I file it down all would be well. Not a factory fit, but maybe good 'nuf with an extra layer of grey bond?!??
 

RustiePyles

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Thanks...I'll look for numbers. I know its not impossible to mismatched head/valves covers to work; but sounds like its a crap shoot.
Indeed, it is possible to run mismatched pieces. I have mismatched head/rocker box on my chopper motor, I got lucky. Often times they will not line up.

..yep, flat otherwise, I suspect if I file it down all would be well. Not a factory fit, but maybe good 'nuf with an extra layer of grey bond?!??

Doubtful, It can cause valve timing issues if they don't fit properly. But if you're a gamblin man, you might also get lucky.
 

gggGary

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I was going to mention filing but it's such a fine art, doing it properly is not all that common. You'll need to have the head back off. A fine large flat file. NO sawing, you keep that file flat across the surface and remove only what sticks up. I find some mineral spirits or other thin cutting fluid with frequent file cleaning helps. NO roto disks, angle grinders, etc the LAST thing you want to do is create a low spot on either surface, which would ruin the part with no recovery..
 

Jan_P

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I have heard of Cylinder heads on Brit bikes ..getting the ?? Misuse
Kan be of interest
Having a flat surface like a glass pane marble stone or steel
that is larger than the item getting the treatment
The cylinder head is moved across / around on that flat surface
I have also heard of wood surface which is not as good
with suitable grinding paper ( Carborundum ) or so on the surface.
In that manner it is more difficult to create a low spot

Not done this myself but heard of Old School people talking about.it.
The Low quality easier to fix the bike yourself ... tale

And as far I can tell also good -->
I find some mineral spirits or other thin cutting fluid
 

lumbee

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Doubtful, It can cause valve timing issues if they don't fit properly..

How so?

I was going to mention filing but it's such a fine art, doing it properly is not all that common. You'll need to have the head back off. A fine large flat file. NO sawing, you keep that file flat across the surface and remove only what sticks up. I find some mineral spirits or other thin cutting fluid with frequent file cleaning helps. NO roto disks, angle grinders, etc the LAST thing you want to do is create a low spot on either surface, which would ruin the part with no recovery..
I know my way around hand file :cool:
 

RustiePyles

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Because you're ultimately limited by the cam bearing bosses, so if you remove material from the mating surfaces that can cause the rocker box to not sit flat which will affect the rocker trunnion to cam center angle which will in turn affect valve timing.
 
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