Best way to test 0 clearance valves?

unless youre starting with a fresh cylinder head and valve job where the machinist tipped your valves at just the right length to get the clearance you want it is a crap shoot

During my last clearance, I ran into similar where next shim size up would have placed me at .16mm which was out of range... Meaning this would have been an order for a new shim and being new would have been .05mm... Now I could have left it in on the low side but I'm anal that way.... :blush:

Anyhoot, in speaking with my grumpy friend Plum he mentioned something I just didn't think about.... In a 30 year old shim, as hard as they are and all, they will loose some thickness!

DOH! :pinch:, sure enough using my caliper on some older shims I have, found a shim in the range needed to keep me under the desired range for ideal clearance in my build....

As Plum mentioned, yes all exhaust sides are hotter but the point I was trying to get at was performance builds will run even hotter....

Anyhoot, measure and you'll find the right size desired... If you stay with spec clearances you'll be good....

OMR

.015mm = .0059"
.016mm = .0006"
.017mm = .0066"

You guys go way overboard on valve adjustments.

On race engines, I'll run .008 - .0010" on the exhaust side with .006 - .008" on the intake side.

Make no mistake, it's very good to pay attention to details but there are times when a half thou is a mile and times when it's nothing to worry about...

staniel wrote:

Yeah, I gotcha, and that makes sense. But let's take a weird scenario.. I have a one cylinder bike.... .

???

larrycavan wrote:

.015mm = .0059"
.016mm = .0006"
.017mm = .0066"

You guys go way overboard on valve adjustments.

On race engines, I'll run .008 - .0010" on the exhaust side with .006 - .008" on the intake side.

Make no mistake, it's very good to pay attention to details but there are times when a half thou is a mile and times when it's nothing to worry about...

I'm not ball busting, just correcting for the sake of correctness here. It should read as follows:
0.15mm = .0059"
0.16mm = .0063"
0.17mm = .0067"

I also think that you meant to say that you would run 0.008" to 0.010" on the exhaust side.

In any case I completely agree with what Larry has to say here. First all of the translation back and forth between metric and inches can lead to math errors quickly. Second, if you think that you can even tell the difference between 0.15mm and 0.16mm with a set of feeler gauges, then your kidding yourself. Third, if you think that you can measure down to 0.01mm accurately with a set of calipers, then you should check your measurments to a good OD micrometer, or check your calipers against a calibrated gauge block. Calipers are guessing sticks when it comes to those close measurements. Although the lcd screen on your calipers goes to 0.01mm if you check the specifications it is likely not accurate to any better than 0.03mm.

Good point Testa...

Same time, this is all most of us have to accomplish and even the OEM specs are using feeler gauges so again, if you can get it within specs for known tools available, good to go...

Not sure I agree with the caliper thoughts, doesn't truly matter if I do or not, as mechanical engineers and machinists have been using calipers for ages now, I think their measurement capabilities are going to be as close as you can get to accuracy in a hand tool. Close enough for us anyways without using a micrometer, rig set up for measuring microns and such :S :laugh: ....

As Larry menitoned and most of us do the same since we learned off guys like Larry, Plum, Timebomb and several others who have been working on these KZ's as a profession the majority of their lives (racing and non racing engine builds), just use the higher end of the range for the exhaust side versus being on the low side due to addtional heat and you'll be golden...

Old Man Rock wrote:

Good point Testa...


Not sure I agree with the caliper thoughts, doesn't truly matter if I do or not, as mechanical engineers and machinists have been using calipers for ages now, I think their measurement capabilities are going to be as close as you can get to accuracy in a hand tool. Close enough for us anyways without using a micrometer, rig set up for measuring microns and such :S :laugh: ....

This is an area where I have professional experience. I am a machinist, and I use both every day. It is possible to get significantly closer with a good OD micrometer than a caliper. I routinely machine parts with a tolerance that is down to 0.00016" or 0.004mm and when checking on the shop floor the micrometer is the only way to go. I back up my measurements with a set of gauge blocks that are traceable to NIST, and also to a Starret Visual Measuring system. I trust my calipers down to a tolerance of about +/- 0.001" or 0.025mm, but I'll take my micrometer for any tolerance tighter than that.

With that said, do your best with the feeler gauges, and get as close as you can with the 0.05mm steps in shim sizes.

Plum's advice for measuring shims is very valuable. Especially when you measure a clearance and order what you think is the right size shim and then the new clearance doesn't come out right.

See there you go... Your one with the knowledge and additoonal tools most of us just don't have... :blush: :laugh:

Ah well, feeler gauge and caliper is good enough... Hmmm, Harbor Frieght has micrometers right? :woohoo: Plum just cringed.... :pinch:

No shim for the size you want, something in between what is sold, right. Well most machine shops will have a magnetic chuck shim grinder, they can shave a shim easily. For us without that we can take a shim to some wet sand paper over a piece of glass, shaving the "Back" side of the shim if new, and checking with a Micrometer to check that the "parallel" has not been changed. .0005" will come off in a few minutes, and a Permanent marker can be used to write the new dimension on the back again.
Used shims should be checked for being "Dished" or "cupped" on the contact side, as this will wear unevenly on your cam lobe, especially with high spring pressures and increased lift. They can be made flat again, then micro polished in the same manor just with a much finer grit.
Nothing fancy just basics.

I tried shaving a 22mm shim on sandpaper and then a hard cutting stone and never got even the slightest bit off. All I wanted to take off was .001". It hardly seemed to even polish the surface. I was told they are surface hardened and the one I was working on was the hardest piece of metal I have ever run into. gave up after my arm got tired.

I've done both the little 13mm and the 29mm with great results. It will take some time with a bigger material loss in mind. Parallelism between the two side is very important, the more you take off the more apt to loose this, careful measuring is the key.

yep..typos.... and .017mm is .006929" not .007 :laugh:

I've seen more than a few old aftermarket cams where you'll get up to .002" lash variance depending on where you position the base circle.

.001" in lash is nothing compared to.001" in shell bearing clearance

I know a guy with a whipped set of 8x Andrews in a 1327 motor that ran 5.95 1/8th last Friday night. His valves are at .006 - .008" across the board. When I say whipped I'm talking lobe tips that are all starting to point out :lol:

Personally, I'd toss them but he can't afford cams at the moment so he's running them...