Simple one - 325i valve lash

[RB5_245]

Could anyone tell me the valve lash for these? mine's an '88 btw.

Just picked one up from a mate and it sounds a bit like a sewing machine with a bent needle.

What a brilliant engine though! great noise (not the rattle that is). I'd only driven a few 4 pot BMs before this.

Oh and firing order could save me a bit of time, but no odds really. Is there a torque setting for the cam cover?

Cheers
Dave

(could have searched for this I suppose but oh well)

[liam012]

valve lash - is that clearances?
if so look no firther than:
http://www.e30zone.net/modules.php?name ... echnva.htm

[MrDazzle]

'lash' is the proper engineering term for clearances, such as valve clearance, in moving assemblies.

[Templ8e30]

Welcome to the E30zone

There's no specific torque setting for the rocker cover, just don't overdo it and strip the threads

Firing order is 1-5-3-6-2-4.

Cheers,

Iain T

[RB5_245]

Thanks guys.

[RB5_245]

0.25mm for inlet and exhaust? (taken from link above) can't be right surely?

I've never seen them recommended to be equal on any engine before.

[handpaper]

Yep, that's right; 0.25mm cold, 0.3 mm hot.

[Brianmoooore]

'lash' is the proper engineering term for clearances, such as valve clearance, in moving assemblies.

Sounds decidedly American to me!
My dictionary makes no reference to machinery under "lash", but "clearance" has a reference to the distance between parts on machinery.

[RB5_245]

I would only use lash in reference to cam driven applications, I don't know why.

Just looked it up on the internet too, no idea where it comes from. Never thought of it as sounding american??

Handpaper, if you set the 'clearance' at 0.3 hot, then it will be even larger than 0.3 when cold.

Sure it's not something like 0.3 hot side, 0.25 cold side?

[handpaper]

Nope, same clearance both sides.
And gaps/holes get bigger when assemblys are heated, too, especially with dissimilar metals.

[nickso]

according to the american manual for my stepmums hyundai, lash is the american word for play or clearance in a technical way.

it goes on about steering lash and such like.

[RB5_245]

oh god, i've been Americanised without knowing it. That sucks

The clearance is there as when hot, the valves and rockers expand. This closes the gap. Otherwise you would set it to near as possible to 0. If you think about it, as they're 2 different things set in place (as such) the only way they can expand is out - toward each other.

Anyway, I'll set them both to 0.25mm. Cheers for the help.

[Brianmoooore]

The clearance is there as when hot, the valves and rockers expand. This closes the gap. .

But there's a big chunk of aluminium alloy between them which pushes them t'other way!

[MrDazzle]

As far as I've seen/used the term, 'Clearance' is for bits that never touch (i.e. that are meant to clear each other) and lash is for slack/play/etc. between bits that do.

[handpaper]

The clearance is there as when hot, the valves and rockers expand. This closes the gap. Otherwise you would set it to near as possible to 0. If you think about it, as they're 2 different things set in place (as such) the only way they can expand is out - toward each other.

Anyway, I'll set them both to 0.25mm. Cheers for the help.

The clearance is there to ensure that, even after a service/check interval of wear, the valves will still close fully and seal on their seats. Noisy tappets will be noticed and get checked whereas a poorly seated valve (especially on the exhaust side) may not be apparent until it has melted and destroyed a piston.
The valves and rockers are not the only things to expand - the whole cylinder head does, too, in *all* directions. It gets longer, wider and taller. Since it's aluminium, it expands more than the valve stem/rocker combination, which is why the clearances are larger when hot - to ensure that when the engine cools, there's still sufficient clearance.

Damn you, Brianmooore - beat me to it!

[RB5_245]

As far as I've seen/used the term, 'Clearance' is for bits that never touch (i.e. that are meant to clear each other) and lash is for slack/play/etc. between bits that do.

That seems to make sense. I'll stick with that description.

[RB5_245]

The clearance is there to ensure that, even after a service/check interval of wear, the valves will still close fully and seal on their seats. Noisy tappets will be noticed and get checked whereas a poorly seated valve (especially on the exhaust side) may not be apparent until it has melted and destroyed a piston.
The valves and rockers are not the only things to expand - the whole cylinder head does, too, in *all* directions. It gets longer, wider and taller. Since it's aluminium, it expands more than the valve stem/rocker combination, which is why the clearances are larger when hot - to ensure that when the engine cools, there's still sufficient clearance.

Damn you, Brianmooore - beat me to it!

So you're aiming for, that if you set 0.25in say the summer, that will allow enough leeway not to hold a valve open the in middle of winter? If i can be bothered I'll do a before and after check when i do mine.

However, this is in contradiction to the operating condition or every other engine i've worked on in the last 8 years as an engineer (petrol and diesel , 2 and 4 stroke of all sizes).

Gives me a bit more motivation to get out there and do it now

[handpaper]

I think wear would be more of a factor than ambient temperature, since liquid-cooled engines operate at...operating temperature, controlled by a thermostat.
It's a fairly quick and easy job (I like eccentric adjusters ).

[MrDazzle]

The clearance is there as when hot, the valves and rockers expand. This closes the gap. Otherwise you would set it to near as possible to 0. If you think about it, as they're 2 different things set in place (as such) the only way they can expand is out - toward each other.

Anyway, I'll set them both to 0.25mm. Cheers for the help.

The clearance is there to ensure that, even after a service/check interval of wear, the valves will still close fully and seal on their seats. Noisy tappets will be noticed and get checked whereas a poorly seated valve (especially on the exhaust side) may not be apparent until it has melted and destroyed a piston.
The valves and rockers are not the only things to expand - the whole cylinder head does, too, in *all* directions. It gets longer, wider and taller. Since it's aluminium, it expands more than the valve stem/rocker combination, which is why the clearances are larger when hot - to ensure that when the engine cools, there's still sufficient clearance.

Damn you, Brianmooore - beat me to it!

To expland on this point...

The valve are hardfaced, that is, the surfaces that contact the cylinder head are err...hard! With hardfaced valves you have to press them shut quite a lot to get a good seal, so you need some clearance in the valve train so that the valves will always have a good solid force holding them closed and providing a good seal.