M20 rough idle

[duffyboby]

hi guys, not too long ago I started experiencing a weird idle issues, this came right after adjusting the valves, it doesn't bounce off idle like it would if it was an icv problem, it idles like if it was a cammed V8, the idle is straight a 600 rpm, no problem at all there, and just off idle it revs perfectly smooth and has lots of power up to redline. now i didn't adjust the valve myself, i did it with an old mechanic that had worked on old bmw's all his life, we changed all that is required when removing the cover, valve cover gasket and the 4 rubber thigny at each end of the head. now two things, he told me he adjusted the valves a tad tighter than specs to compensate for the wear of the engine, and it is not the valve cover that was on there before, it is one i sandblasted and painted. i am a little concerned it might of been warped (if thats even possible) and letting air go into the valve train while the engine is running, i would've tried putting my other one back on but i dont have access to it at the moment. i have looked around forums and youtube trying to find something similar but can seem to find anything, has anybody ever experienced this problem? i am quite confused as to what could've caused this after a simple valve adjustment, it was running perfectly fine the day before.

[Cabriolet]

you didnt adjust your valves correctly.

the engine must be dead cold
.01" feeler gauge
measured under the eccentric - top of valve
should be snug to pull in and out the feeler when tight. but not hard or loose.

[duffyboby]

He told me they are at .008, so i guess ill be redoing those

[Cabriolet]

He told me they are at .008, so i guess ill be redoing those

well there u go. easy fix! .008 is good for tack only. but .01 is what you need for a DD car.

[duffyboby]

Perfect thanks a lot!!

[duffyboby]

Just out of curiosity, how would the engine benefit from valves a bit tighter for the track? What advantages does it give!

[Cabriolet]

Just out of curiosity, how would the engine benefit from valves a bit tighter for the track? What advantages does it give!

it's like having a cam with higher lift and longer duration. i believe the spec guys do it to get more power from a full stock engine.

[duffyboby]

it's like having a cam with higher lift and longer duration. i believe the spec guys do it to get more power from a full stock engine.

I get it, thanks!

UPDATE: Valves where really too tight, its what caused the rough idle, purrs at idle now, set at .010