Engine breathing

[GavinL]

I have a 68 saloon with a 1098 engine, however it has twin SUs from a MG Midget. The engine has the standard tappet cover open tube vent, and a replacement rocker cover with an unvented filler cap and no vent connection. I'm assuming from other threads there may be insufficient venting of the engine and I need to add a vent to the rocker cover as a minimum? Also I've picked up Tappet cover with an oil interceptor, and I'm considering fitting it and connecting it to the carbs the same as the Midget set up. Any comment/ suggestions welcome.

[edd_barker]

Loads of info on this on the forum, quick search will dig it up!

General consensus, fit tappet cover breather (ensure correct one or it will foul rad hose) and plumb to carb. No rocker breather required as long as filter cap is vented.

Edd

[GavinL]

Thanks - yes i'd found a lot of the info on the forum, just wanted to check - i was curious if i need to change the existing tappet cover pipe, as it is obviously original, but i was wondering if they are prone to 'leaking' oil - i remember on british bikes it was common practice to route the engine breather to discharge over the chain to help keep it lubricated! also my rocker filler cap isn't vented, and the cover cant take a normal vented filler ( it is a chromed after market type) so i assume i'll have to change it for a standard A series which will take a vented filler, which fine as my wife hates the shiny one So i'm on the lookout for a standard rocker cover, and they appear plentiful on eBay.

[IslipMinor]

Gavin,

Yes, if you have a crankcase ventilation connection on the carburettors, then connect that, via a 'Y' piece, to the oil separator on the front tappet cover and fit a vented/filtered oil filler cap to the rocker cover - no vent hose from the rocker cover!

The system uses a small amount of vacuum from the throat of the SU's to create a partial vacuum in the crankcase. That in turn draws in fresh, filtered air through the oil filler cap and also helps to reduce the oil leakage past the rear main scroll (no rear main crankshaft seal as such).