Rocker Cover Breather - Is it necessary??

[K4TRV]

There is a thread running within the TVR Speed Champs participants on the need to extend the Rocker Cover "breather" via a pipe to a catch tank. MSA Blue Book - Section S 10.3.5 refers unless the system uses a closed loop system for the oil breather system.

During scrutineering prior to a Sprint/Hillclimb, some Scrutineers have deemed the standard breather is likely to lead to oil being deposited on track, therefore, requiring pipes and a litre catch tank. I have other Scrutineers say the Rover has a closed oil system therefore the breather isn't deemed part of the oil system.

So whats the use of the breather, surely not for the oil breather system ?? It has a needle sized hole which allows air into the rocker cover via the v small foam filter - nothing to do with the oil system ???

Can anyone tell me if I block the breather, that is seal it up, it won't interfere with the engine breathing/running??

I just can't see with 4 litres (plus) of swept volume/air in the sump/valley that a needle sized breather at the top of the Rocker cover will do anything really to the "Oil System".

Can I block it up and therefore remove the need for a pipe and a catch tank????

Comments, speculation or even the "truth" on the breather would be appreciated. Tks

Trev

[CarlosV8]

From what I gather through rebuilding the EFi system on my old SD1 Vitesse (flapper rather than hotwire, but should be the same principle) this breather is very important to the crankcase ventilation system. Air is drawn in through the LH breather, and due to the vacuum in the plenum dirty air is drawn out through the RH breather and burnt off through the engine. The wire mesh in the RH breather helps ensure that no actual oil is drawn into the plenum (although inevitably some will, which is why they can get gunked up).

This air by-passes the air flow meter, therefore must be carefully metered to ensure the engine keeps the correct air / fuel ratio, hence the pinhole size on an EFi engine. If it's blocked off you're gonna stop the breather system from working which isn't likely to yield pleasing results!

Not sure where that leaves you in terms of the MSA. The breather is pulling in air rather than pushing it out, and at 0.040" (just looked it up) I doubt whether oil could even escape anyway. Would connecting the breather to an induction pipe mean it was classed as closed loop?

Cheers

Carl

[K4TRV]

CarlosV8 said:

Snippity.... If it's blocked off you're gonna stop the breather system from working which isn't likely to yield pleasing results!

Not sure where that leaves you in terms of the MSA. The breather is pulling in air rather than pushing it out, and at 0.040" (just looked it up) I doubt whether oil could even escape anyway. Would connecting the breather to an induction pipe mean it was classed as closed loop? ....Snip

Cheers

Carl

Hi Carl,

Tks for your thoughts. Decided not to connect to anything, it's just 0.04"!! Instead of "sorry sir failed scrutineering....." I have removed breather and sealed the rocker hole up. Driven 20 miles locally, and can't feel/see/hear any difference. With such a small orifice (sorry/hole), i just couldn't see what difference it would make. If it does "change" things I can revert easily!!

Off in the morning to run in the TVR CC Speed Champs at Gurston. That'll test it and the Scrutineer, if he notices..........!!!

Trev

[Ant.]

Not sure if I have fully understood your question, but it is commonly known that a sealed RV8, i.e no flame trap or breather inlet , will start to leak via the seals as the pressure builds in the block.

[haircutmike]

I don't know the answer, but when I emptied my catch tank after about 18 months and many T/D's, there was a smidgen of oil and about a small cup full of water in it??

[Pupp]

If the rest of the system is in place, sealing off the mushroom vent will cause oil to be drawn excessively into the inlet on overrun. It is key to the function of the oem system

[K4TRV]

Ant. said:

Not sure if I have fully understood your question, but it is commonly known that a sealed RV8, i.e no flame trap or breather inlet , will start to leak via the seals as the pressure builds in the block.

All is in place (Flame trap/all inlet pipes) except the mushroom shaped valve of the LH Rocker.

[K4TRV]

Pupp said:

If the rest of the system is in place, sealing off the mushroom vent will cause oil to be drawn excessively into the inlet on overrun. It is key to the function of the oem system

Driven 80 miles (40 there and back - quite quickly) to Gurston Down Hillclimb Sat. 2-practise & 2-timed runs. Beat my best time up the hill (now 38.8 secs) and came 4th in TVR Speed Champs with a std 400/888 tyres (but no mushroom valve!!).

Haven't seen/felt any change to engine since blocking/removing mushroom valve. Certainly no reports of a smoky exhaust or increase use of oil.

I'll keep monitoring, but still find it rather difficult to believe a 40 thous hole (0.040") on the rocker has much effect?? Clearly (to me) a throw-back to Land Rover installations which it may have been a key element on their applications?.

Thanks Pupp for your comments.

Trev