Valve Adjustment Below Spec

[Smitsky089]

Hey guys.
I'm in the middle of a valve adjustment for the first time. When I went to check the valves for clearance, it appears that nearly every valve is (significantly) below the spec (too tight). Most intake clearances were about 0.004" (spec is 0.007-0.009"), and most exhaust clearances were about 0.009" (spec is 0.011"-0.013").

I'm a bit confused/concerned how this could be. I figured I would be finding a few valves above the spec and need to add shim thickness. Is it actually possible for the clearances to get smaller as the vehicle is driven, or did the PO possibly adjust the valves incorrectly.

Everything visually looks good, and I don't have any shiny metal on the cam lobe base circle.

Any ideas would be greatly appreciated.

Figured this one might have been asked in the past on M3F, but didnt see anything yet on this forum. Regardless, good to have the forum back!

[andrebxp]

As the valve seats wear down, the clearance will decrease. Adjusting the valves adds the clearance back by using a smaller shim.

[lunardds]

The primary wear is on the valve seat. The valves seat deeper and the clearance gets tighter. Or the guy before you just had diff feeler gauges.

[Desert_M3]

Just re-shim it to get it back to spec, no big deal. And for what its worth, I use MM instead of inches when I do valve adjustments. .18-.23 intake and .28-.33 exhaust. Either way works.

[mrgizmo04]

What size shims are in there now? If they are 2.75mm maybe po didn't do it right. If they are closer to 2.25, then maybe that spells some issues with seat wear.

How many miles on engine? How long ago was last valve adjustment? Visually you won't notice anything, we are talking a few mm (if that) here and there. Engine run strong?

[Smitsky089]

Thanks for the replies everyone!

The valve seats wearing down make sense, I was just shocked there was such little clearance compared to spec.

What size shims are in there now? If they are 2.75mm maybe po didn't do it right. If they are closer to 2.25, then maybe that spells some issues with seat wear.

How many miles on engine? How long ago was last valve adjustment? Visually you won't notice anything, we are talking a few mm (if that) here and there. Engine run strong?

When I just went back out to pull a shim to answer this question, I tried to find the worst case scenario with the smallest gap. To my surprise, it now seems like all valves are 0.006-0.007" on intake and 0.010-0.011" on exhaust, so very close to spec. The only difference I can think of between yesterday and today is that by now I have spun the engine a few times and there is now more oil around the cam, causing the gauges to slide in easier. Prior to this, the engine had not run for 5 months, so maybe that was my issue.

Either way, if the "true" gap is at the low side of the spec, is it still recommended to change in order to get it more in the middle? Example: on intake valve, making an adjustment to move it from 0.007" to 0.008". I am worried that if I need to make a 0.001" correction on nearly every valve that I will eventually run out of a certain shim size in my kit.

[mrgizmo04]

Thanks for the replies everyone!

The valve seats wearing down make sense, I was just shocked there was such little clearance compared to spec.



When I just went back out to pull a shim to answer this question, I tried to find the worst case scenario with the smallest gap. To my surprise, it now seems like all valves are 0.006-0.007" on intake and 0.010-0.011" on exhaust, so very close to spec. The only difference I can think of between yesterday and today is that by now I have spun the engine a few times and there is now more oil around the cam, causing the gauges to slide in easier. Prior to this, the engine had not run for 5 months, so maybe that was my issue.

Either way, if the "true" gap is at the low side of the spec, is it still recommended to change in order to get it more in the middle? Example: on intake valve, making an adjustment to move it from 0.007" to 0.008". I am worried that if I need to make a 0.001" correction on nearly every valve that I will eventually run out of a certain shim size in my kit.

Since the engine hasn't been run for a while, possible there was some dry oil droplets or something else that was preventing you from sliding in the bigger feelers. Within spec is 7-9 thou on intake, so if you are at 7 on some of them, you are in spec, so no need to try to get a smaller shim in there to get to 8thou clearance. Equivalent on exhaust from 11 to 13.

[Tbonem3]

Engine was dead cold the first time?

[Smitsky089]

Engine was dead cold the first time?

Yes, dead cold. Has not run since end of October (winter storage).

[Arith2]

I ran into this issue with my new engine. Cylinder 4 intake valves were both below .005" which is the lowest guage I have on my set. I fixed it but I'm hoping valve seats aren't collapsed or something. I'd say listen to the engine for excessive ticking. Apparently that's how they determined whether our cars got valve adjustments or not at BMW. I bet most of our cars didn't actually get the valves adjusted.