Change Your Flame Guard Filaments!

[Ryan1980]

thanks mate - let me know what you find out!

[HAKO]

To Brettj

My engine is 110983, 280 SE and there is nothing in the breather hose, nor in the air filter housing.

Besides I do not see how these flame guard filaments ' pug up from crud ', once they are fitted in a breather hose, not a blowing one.

Harry

[oscar]

What year is your 280 HAKO?

It seems that the 280's that are supposed to have a flame guard filament are those that have a vent valve rather than a vent jet.  The text says flame guard filaments are used up until 1977.  You can see where the vent valve or vent jet (picture) is located in the first pic below.  If a flame gaurd filament is fitted, it goes where the breather hose attaches to the air filter housing regardless whether carby or d-jet, second picture.  Later carby 280's didn't have them and I think most k-jets don't need them.  Pre 1977 seems to be the changeover so maybe some early k-jets had the filaments but the text doesn't say so.  The defining factor seems to be whether the engine has a vent valve or vent jet.

Re the crud in the filament and the change to vent jets over vent valves: under idle or coasting, fresh air travels through the breather hose into the crankcase.  Under high load or accleration, blow-by gasses moving past the piston rings force oil fumes and combustion byproducts past that vent valve or jet and into the air filter housing for recombustion.  The vent valve I understand is more open under these high load high blow by conditions and is why a flame guard is used and why it can foul up.  I think the vent jet without flameguard combo on later models is because the vent jet is too restrictive in that a flame couldn't travel past the small jet opening.

[brettj]

Hi Oscar,

I think you are correct on the last flame guard question. In looking at the manuals I have, it seems that 1974 models  definately still used flame guards carrying over to 75. Looks like 1976 might be the last year for them.

[koan]

The M-B folks must have had a change of thinking around '74 or '75 and done away with the valve (and flame guards) and gone for the restricting jet.

The 6.9 vent diagram shows it to be bi-directional. At idle and part throttle air from the air filter enters one rocker cover, passes through the engine and is drawn out the other rocker cover through a small orifice or jet located in the idle speed / aux air valve / warm start casting and finally into the inlet manifold. At full throttle it shows blowby gasses exiting both rocker covers.

The text in oscar's pic mentions white arrows but I can't see them, are there two vents on the 280 engine so it could work in the same way?

koan

[Niclas]

Checked yesterday, didn't have any on my -75 euro 450. But as I mentioned in other threads I had a whole shit load of soot and varnish stuck in my intake manifold. My car don't have any restricting jet either.

Conclusion: Filaments are (fila)ment to be there.

/Niclas

[13B]

My 1975 engine in my 450SE has them.

I bought a couple of cam covers off Noel which came from his 1974 450SEL, and it didn't have them.

Go figure.

I.