Head resurfacing, should I degree the cams?

[Guest]

1978 gs550e

I have the head off, the gasket surface is warped and is going to need at least 0.009 milled off to be flat and level.

If I proceed to have the head resurfaced, would the cams being 0.009 closer to the crank make a noticeable difference to the timing?

Any source for slotted cam sprockets, or thicker head gasket?

 

[Big T]

That's not enough to worry about

 

[Guest]

Thank you. I have reconsider another way of measuring the head. I'm using a surface plate and a dial indicator.

Considering the head, the gasket surface is supposed to be parallel to the cam bores.

It may be that the intake cam bore is deeper then the exhaust, for I'm getting a sloped reading as I move my dial indicator from the intake side to the exhaust.

 

[zed1015]

Are you wanting to skim the head because you have gasket sealing problems or is it that now it's off you have found that it is VERY SLIGHTLY warped ?
If it's the latter then leave well alone.
Skimming a warped head can cause cam binding issues once the head is torqued down as it will throw the cam bores out of true.
The first line of action is to bolt the head to a surface plate, heat it in an oven and let it cool to true it up.
For that tiny 0.009" (0.09mm) i'd leave it alone as it will be rectified once the head is torqued back down.
As for the cam timing.
Even from the factory they are never spot on to the design specs due to manufacturing tolerances in the deck heights etc so that 0.009" won't make a difference but from a general point of view degreeing in the cams even on a stock bike can sharpen up the motor depending on which end of the tolerance range they are at.

 

[bwringer]

Are you wanting to skim the head because you have gasket sealing problems or is it that now it's off you have found that it is VERY SLIGHTLY warped ?
If it's the latter then leave well alone.
Skimming a warped head can cause cam binding issues once the head is torqued down as it will throw the cam bores out of true.
The first line of action is to bolt the head to a surface plate, heat it in an oven and let it cool to true it up.
For that tiny 0.009" (0.09mm) i'd leave it alone as it will be rectified once the head is torqued back down.
As for the cam timing.
Even from the factory they are never spot on to the design specs due to manufacturing tolerances in the deck heights etc so that 0.009" won't make a difference but from a general point of view degreeing in the cams even on a stock bike can sharpen up the motor depending on which end of the tolerance range they are at.

We need a "like" button... I agree that the OP is splitting hairs that don't need to be split.

Also, bear in mind that this is not a water-cooled engine; the only places that need to seal are the "fire ring" in the gasket in a circle around each cylinder and the four oil passages at the corners. After 40+ years, some cylinder heads have some pretty grungy surfaces in those in-between spaces, but that also doesn't really matter. You can do far more harm than good and remove way too much metal by trying to clean up the entire surface.

 

[Rijko]

Skimming a warped head can cause cam binding issues once the head is torqued down as it will throw the cam bores out of true

Zed, could you please explain how skimming .009 inch
could cause that ?

 

[zed1015]

Zed, could you please explain how skimming .009 inch
could cause that ?

If the head is warped in it's free state then the whole casting is warped including the cam journels but when it's torqued in situ the whole thing is pulled straight on the block and the journals run true.
If you skim the warped head then the gasket face will be true but the casting won't be pulled straight when torqued down which leaves the cam journals in the free state warp which can cause the cams to bind.
The severity of course depends on the ampount of initial warp and the tolerance of the cam journals.
0/009" is negligable and won't cause any issues and as previously mentioned any warpage on these types of heads should be relieved by bolting the head to a surface plate and heat normalised to true up the entire casting.