[링크] Valve Adjustment - M30 Big Six

Link: http://member.rivernet.com.au/btaylor/BMWText/technical/SettingValvesM30E28.html

Valve Adjustment - M30 Big Six

From: "Brett Anderson" <Bretta@bestweb.net>
Date: Fri, 5 Jun 1998
Subject: Re: M30 Valve adjustment too tight? (Brett A.?) BA

> From: Benjamin_Trapp@Dell.com
> Date: Fri, 5 Jun 1998
> Subject: M30 Valve adjustment too tight? (Brett A.?)
>
> Okay, I was able to quiet the valves down by tightening up the gaps.
> Some were a little loose, but just for kicks I gapped them really tight
> and now they're at about 9 thousandths. Man, the car has excellent
> throttle response now! Only problem is that it's "camming" right now
> and has a lumpy American V8 idle that shakes the car. I took off the
> plug wire to the No. 2 cylinder and that smoothed things out. So I
> probably have some carbon in my No. 5 valves and will check it out
> this weekend. (Any ideas on why this cylinder is acting up?)
> Here's my question: I know the gaps are supposed to be between
> 12 and 14 thousandths, but they were too loud at 13. I want to adjust
> them again tomorrow and was wondering if leaving them at around 10-11
> thousandths would be okay. Many of you M30 owners say you gap yours
> to10 thousandths anyway--do you guys have any problems? Brett, what do
> you think? Will my rocker arms snap at 6800 RPM (I have a Jim C chip)
> if they're this tight? Accelerated cam wear? The valves are very quiet
> with things as tight as they are now and I think if I can check the
> adjustment on the No. 5 cylinder, the whole engine should be smooth and
> quiet again. I want to make sure I'm not going to driving a
> ticking-time-bomb when I put that valve cover back on for good.
>
> Thanks,
> Ben
> benjamin_trapp@dell.com
> PCA / IDSA / CIP / BMW CCA #156642 (NCC)

Adjusting the valves this tight causes misfire at idle, your HC will be through the
roof, you will probably fail any emissions sniffer test the car needs to go through.
You will also run severe risk of eating the cam in a very short time. The system is
designed for 12 -14 thou, it has been my experience, along with many others,
that 14 thou, dead cold, is ideal. Attempting to quiet the valves is a stupid idea,
if you want your engine to run as quiet as a Honda, buy a Honda. You should be able
to hear every single valve, plus the clicking of the injectors. If the valves are louder
than the injectors, the valves are due for adjustment. If the injectors are still louder
than the valves, you are ok
( Note: When I recently had a cam installed, the valves were set to 13 thou cold, then
with the engine hot, each valve was checked to make sure it was set at exactly
14 thou. I'm told this delivers the best performance. Many Mechanics set them
to 13 thou warm, because it saves time not having to wait for a cool engine. Ed. )
Brett Anderson
BMW and ASE master technician
http://frontpage.bestweb.net/~bretta

---

From: Don Eilenberger <dje@mail.bellcore.com>
Date: Mon, 20 Feb 95
Subject: RE: E28 valve adjustment Q's

Aaron asks:

> The Bentley manual specs the following for both
> intake and exhaust gaps on my 88 528e as:

> cold: 0.010"
> hot: 0.012"

>Is the book wrong? It seems to me, the wider gap
>should be used when cold. Am I mistaken to think
>not all metals have a positive coefficient of expansion?

>Also, how 'slight' is a 'slight drag' in Bentley terms when
>using the feeler guage?

To which I answer - the book is wrong - but not about what
you think.. IF it was possible to adjust the valves with the
engine hot - larger is the way it should go, since we're
talking about expansion of LOTS of metals here - the valve
stems, the camshaft, the camshaft mounts and the head.. which
brings up why I consider the book WRONG on this point:

I have NEVER - EVER been able to do a reasonable valve
adjustment on a car with an aluminum head when it's hot -
'cause it doesn't stay at the same temperature long enough.
On BOHICA - when I tried it, I did from front to back, and then
as is my usual proceedure, went through them and checked them
all - and ALL the front ones were now too tight - the engine had
cooled enough to change the settings - even from front to back.

SO - what you SHOULD do is let the engine cool overnight -
preferrably at 60F or above - and use the cold settings, without
starting or running the engine for more than a few seconds. Doing it
this way I can get repeatable readings when I do my check run
through after doing the adjustment.

As far as what they mean by slight drag - until you're used to it
and get a real feel for "slight-drag" - use a feeler 0.001" over and
one 0.001" under in combination with the correct (0.010") one. The
over should go through with noticable effort - the under should slip
right through - and the correct one will go through with "slight-drag"..

Don't get anal about the adjustments - within 0.001" is probably close
enough - and it's better to err on loose than tight (loose=noise,
tight=burned valves). After you do it several times the eccentric
adjuster won't seem such a stupid idea... and lots of times what
sounds like valve noise is actually injector noise - under certain
conditions they can be quite noisy (at least as noisy as the valves),
a stethascope will help you to determine which noise is which (as will
a long screwdriver with the handle to your ear, and the tip touching
the various parts).

Best of luck - Don Eilenberger

---

Date: Wed, 10 Feb 1999
From: Dave Kan <dkan@america.net>
Subject: Re:Bad running E28

Snip...
There are other things to try to fix the idle on an E28. Check for
vacuum leaks such as your hoses and your oil filler cap and your oil
dipstick. Adjust your valves to .012 while the engine is cold. I tried
to adjust them to .014 but got plenty of noise and clatter and lost some
power. Adjust your spark plug gap on your silver plugs (always WR9LS)
to .035
Snip...

Good Luck.

I am not an expert. Just a man on an endless journy to smooth out my
car's idle.

Dave Kan             ______'86 535i 200K      o/______\oBMW CCA 154020     (oo=00=oo)                   []=----=[]