Shape of a Camshaft

[pkboxer]

Straight to the question, is TDC the "loosest" that my valves should be?

Or is that just where you set them?

I checked my valves (again) last night after valve noise and internet posts suggested I may have been setting them too loose.

Anywho, the exhaust valve was "inactive" when I removed the valve cover, so I just measured it and it was way loose (like loose with the .025mm feeler, I think my decimal is in the right spot??)

But after I put it at TDC for that side, it was actually tighter, closer to spec, but still loose.

I thought at TDC, that was as loose as it gets, is that not right???

[macdaddy]

Are you on compression?

[pkboxer]

Macd - I'm not sure where I was.

I did the valves just fine at TDC, the only question I had was that I thought the clearance would be the same until it started to close up, eventually becoming "0" and the valves where "active".

Is there a spot on the cam where it should/could be looser (ie. bigger gap between valve and lifter) than at TDC?

[pkboxer]

I think I'm explaining this poorly.

If you see the animation on this page, is this the shape of our cam lobes? Peap shaped?

http://en.wikipedia.org/wiki/Cam

if so, at TDC you have a gap, and then it should only ever be less than this.

At some point, just where it happened to be at when I removed the valve cover, but before setting at TDC, I measured a larger gap on my exhaust valve.

That seems wrong, yes it can always be user error, but I was wondering if this points to some issue.

Bike it running just fine....

[Deleted User 62]

Short answer, no, but are you adjusting each cylinder at top dead center? Use the kicker if you have one, or rotate the engine with the alternator bolt or rear wheel. You should see the intake valve open, then close, this is where the Top Dead Center for that cylinder should show up in the timing hole. Then rotate the engine again to do the other side. Note: there is some leeway either side of TDC for maximum lash, but it should not be more at that point, best to use TDC as baseline.

[Kurt in S.A.]

What Tim described is correct, but I think it should be added that you will have found TDC "on the compression stroke". That is an important aspect for setting the valves. Once you see the intake valve begin to close, you're heading to TDC on the compression stroke for that cylinder. You need to then watch for the OT timing mark to show up in the window as you continue to turn the engine. There is another TDC for the same cylinder...it just that the cylinder will on "on the exhaust stroke". Not the same thing.

Kurt in S.A.

[Deleted User 72]

A fool proof method I always use (important in my line of work) is to get one set of valves "rocking", that is, both valves moving at the same time. Then adjust the OTHER side's valves. Turn the engine 1 rev and repeat for the opposite side. There is enough room on the off side of the cam that deadly accurate TDC is not necessary.

[pkboxer]

OK, I am 100% sure I know TDC (even though I was typing TOC in the original post) and 100% on the correct side.

I was just curious because after removing the valve cover, before setting at TDC, the exhaust valve was not active (wasn't being acted upon by the cam, for lack of better explaination) and I measured the gap and it was larger than the gap when it was at TDC.

I thought that didn't seem right but didn't try to recreate it.

It wasn't that the valves had no gap at TDC, they were fine. It was that I had a larger measurement for the gap, somewhere else on the cam.

[melville]

When you are at TDC on the left side compression stroke, the right side is at overlap. Both right side pushrods are under pressure, and that can move the cam toward the left by the amount of the bearing clearance. A few degrees after TDC and the right exhaust will be off the ramp, possibly letting the cam rest in a more neutral spot, and with a little pressure applied via the feeler gauge shoved in under the rocker the cam can be shifted a touch toward the right. This would appear to be a larger valve clearance. Similar for a few degrees before TDC and the intake valve.

Not a big factor with stock T1 VWs, as they have nearly no overlap, but I've seen similar effects with aftermarket cammed VWs. Airheads are like VWs with BIG cams.

[pkboxer]

Melville, thanks.

That's exactly the type of answer I was looking for.

What could/would make for a "gap" larger than TDC.

I kept reading the responses and the rereading what I posted to see what I was saying wrong.

Sometimes, with forums, someone gets down a road with the answer and all the follow up takes you farther down that road.

Especially on things that are hard to explain in print, rather that if we were talking in person.

Thanks everyone.

Now, no one say that Melville is full of it and I have bad bearings!