Valve Clearances adjusted = lumpy idle??

[Wid77]

I know there are quite a few posts about adjusting valve clearances but i can't quite find the information i need. Can anyone give me some advice?

I have an 88 325i touring (standard M20 engine) which had the usual ticking noise. I took the head off at the weekend and adjusted the clearances as shown in the helpful technical article. The only thing is that i got a bit carried away and set them at a 'tight' 0.20mm as i though they would need to be tighter than 0.25mm as the engine has done a highish mileage (127k). The engine was stone cold. I also changed the spark plugs for new Bosch ones (gap 0.7mm) as the old ones were all of different makes and at least one was ancient.

Well, the engine is much quieter as you would expect but it has a very lumpy idle. It does seem to have a little bit more power, especially higher up in the rev range. I am now worrying that the clearances are too tight and i may adjust them again at the weekend to a tight 0.25mm. Could the reason for the poor idling be down to the valve clearances or do you think it just needs a tune?

Thanks for any advice

[Ant]

set the clearances to the correct spec ASAP dude.

once set tight and up to running temp they will not fully close to the seat, the risk of burnt out valves is v high

the specs are not a guide, they are gospel dude

[Wid77]

Thanks for that advice. I better try and sort before the weekend then! Do you think this may be why it is has a lumpy idle?[/img]

[ian332isport]

Do you think this may be why it is has a lumpy idle?

Yes.

[GDBN]

When I put the new head on my 325 the guy who put the head together set them at 0.20 - I had a crap idle with stalling and all sorts of rubbish. The engine can't "breathe" properly with them that tight. Set them back to 0.25 and look for other problems,

G

[Wid77]

Thanks for that. I didn't think that .05mm would make that much difference but obviously it does. Will get it sorted asap.

Cheers.

[Mops]

I know, 0.05 is ridicolouslt small, especially for low tolerance engine like m20. I did mine to 0.22 on cold and it is sweet ass
after all, you have to compensate for the wear af 120k+ miles...

[Toby_Unna]

what are you on about when you say compensate for wear

the valve clearances are adjustable so you can compensate for the wear, you're supposed to adjust them back to the factory setting

if it sounds 'sweet as' i'd imagine you mean the top end is very quiet sounding. that isn't a good thing.

[Mops]

noy are not absolutrely silent. i still kinda hear them, but they are not as intrusively loud as before. by compensate for wear i mean compensate for wear on cam lobes and rocker arms.