i decided to check my valves today on the Z6 head. the manual says the clearances are supposed to be .18-.22 for intake and .23-.27 on the exhaust. put the 1st cylinder at TDC, tried to slide a .18mm feeler gauge between the top of the valve and the end of the rocker amr. i really expected more than .22 cuz i have never checked before and this thing has about 60k miles on it. but the gap came out to be .127mm !!! it's even smaller than the allowed lower limit! how is this possible? i mean, the gap is supposed to get bigger w/ age, right? and if the previous owner of the head had done a valve job on it, why whould anyone set the gap to be so small? the car runs fine, i've put about 2.5-3k miles on it since the head swap..

btw, other cylinders are close to the same, it's either .127 or .152 on the intake. the exhaust is also smaller than it should be, but i forgot the values i got.

could someone tell me if im doing something wrong here? and if not, then does anyone know why there would be such a tiny gap on my head?

 

Are you sure you are not mixing mm's and thousandths on your measurements or your feeler guage? BIG difference. I would think somewhere between .005 to .015 thousandths would be normal clearance on most Honda heads.

 

yea, im sure. at least that's what the helms manual says...

 

Just wondering did you check the valves when your car is totally cold?

 

yep, the car was off overnight and it was about 40F outside at the moment...

does anyone know if im checking it correctly and in the right place? if i check the gap between the cam lobe and the pusher, whould it not be the same?

 

I just figured out what your problem is. It is the statement that the valve clearance should get larger with age. Actually, the oposite happens. As the valve seat in the head wears out, it allows the stem of the valve (where you are checking your clearance) to actually raise itself deeper into the head. As the valve wears out, it does the same thing. So for every mm the valve and seat wear out, you lose 1 mm of valve clearance.
Example: You set your valves at .012 clearance. Over time, the valve face wears .002, the seat wears out .003, your new valve clearance is .007.
Earl

 

earl, thanx for the info, this makes more sense

ok, i adjusted the vales. the gaps were too small, so i increased them to the honda spec values. but now they are knocking!!! how is this even possible? they didnt knock before and i had tiny gaps. now that i've increased the gap the valves should be going in less than before. therefore, they cant hit the pistons. but there is a deffinite knocking in my engine after about 2.5-3k. and i tightened the lock screws good. and i rechecked the gap before closing the valve cover. i dont understand, can some one please explain this phenomenon that's happening to my head?

 

Tighten them back up and see if the knocking goes away. If valves are too loose, there should be more of a metalic click or tapping noise on top. I still think you may be mixing mm's and inches in your adjustments. Anywhere from .006 to .012 (in general) measured in inches should be your clearance...I admit I don't know the specific clearance on your engine but Helms gives you measurements in mm and in, so be careful.
PS: A quick way to check your valves is to put the eng. on #1 TDC. Check Intake and Exhaust. Then check the Intake of #2 and then the Ex. of #3. Rotate the engine 360 degrees at the crank putting #4 at TDC. Adj #4 Intake and Exhaust, Then #2 Exhaust and #3 Intake. Saves you the time of finding TDC on all cylinders and you just need to line up the timing mark twice.
BTW, #1 cylinder is the one nearest the timing belt.
Good luck