Combat breather modification

Fritz · Oct 10, 2008

Hoping to settle an on-going debate with a mate of mine. Discussion centers on performing the modification by moving the breather to the timing case.

Question is, would doing the mod AND leaving the original breather also in place (rear of crankcase) be a bad thing...or does the original need to be blanked off? Thanks in advance for any opinions!

Hortons Norton · Oct 10, 2008

There is a bit more to it than just moving the breather, You need to machine the cases for the oil to have a place to pool and return. Look it up on the Old Britts site, Chuck.

Fritz · Oct 10, 2008

Hortons Norton said:
There is a bit more to it than just moving the breather, You need to machine the cases for the oil to have a place to pool and return. Look it up on the Old Britts site, Chuck.

Yes, that being said, if the case was machined for the oil pickup would the fact that both breathers are present be a bad thing? Or would it be absolutely necessary to install a blanking plate over the original breather?

Hortons Norton · Oct 10, 2008

I guess you could run a t in the line and do it that way, But why would you want to do it that way? Chuck.

L.A.B. · Oct 10, 2008

Fritz said:
if the case was machined for the oil pickup would the fact that both breathers are present be a bad thing?

I don't see how having the two breathers could do any harm?

bill · Oct 10, 2008

<I don't see how having the two breathers could do any harm?>

It could try to push oil up the breather hose. not saying it will just a possibility with it so close to the sump pickup.

windy

L.A.B. · Oct 10, 2008

bill said:
It could try to push oil up the breather hose. not saying it will just a possibility with it so close to the sump pickup.

Bill,

Apparently, that can happen with the rear crankcase breathers anyway, if the sump is full of oil on start-up, according to at least one of our members, the excess oil simply returns to the oil tank via the breather tube rather than through the scavenge pump.

I don't see how having an extra breather could increase crankcase pressure over that of the original so that it would be likely to cause any kind of problem, as the crankcase modification can be done successfully without the breather modification being needed, as far as I know?

grandpaul · Oct 10, 2008

As long as you route the rear breather hose vertically to as high a point as possible to reduce the chance that oil could easily flow back to the breather inlet of the oil tank, it's not a problem.

L.A.B. · Oct 10, 2008

grandpaul said:
As long as you route the rear breather hose vertically to as high a point as possible to reduce the chance that oil could easily flow back to the breather inlet of the oil tank, it's not a problem.

Would there be much point trying to route a breather hose to "as high a point as possible", as it would be difficult to route it significantly higher than the ('72) oil tank breather inlet anyway? In any case, what would be the problem with a certain amount of oil finding its way to the tank through the breather?

grandpaul · Oct 10, 2008

You're correct, I was thinking of the air box inlet; different bucket of pig's feet.

Combat breather modification

Fritz

Hortons Norton

Fritz

Hortons Norton

L.A.B.

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bill

L.A.B.

Moderator

grandpaul

L.A.B.

Moderator

grandpaul