Tick-over question re. the crankcase breather pipe

[Waynebaby]

Hi All,

 

I've noticed that if I take the crankcase breather pipe off the rocker cover on my Mk3 GT6 (or remove the oil filler cap) whilst it is ticking over the tick-over rate increases slightly and the engine runs marginally smoother. Does anybody happen to know if this is normal or is it indicating that there is something not quite right? I don't know if it is relevant or not but there is next to no blow-by through the oil filler cap.

 

Wayne

[Pete Lewis]

the breather is pretty much a sealed crankcase  the manifold creates the vacuum to disperse any oily fumes and they get re burnt, taking a hose or filler cap off opens the system and the in going air bypasses the throttles and the engine will then speed up, 

 

if it seems to run better with the cap off then there's some basic mixture and idle settings that are unhappy.

 

Pete

[Waynebaby]

Thanks Pete,

 

The car runs pretty well just now so rather than fiddle with the carbs I think I'll leave well alone.

 

Wayne

[John Bonnett]

My GT6 ticked over much better after I'd sealed off the carbs and ran the rocker cover breather through an open ended pipe.

[Red Devil]

Mine is identical to John. I have a pipe from the rocker cover to under the car and it is much better.

[JohnD]

RD,

An open pipe is just a touch antisocial, in an age, when cars are expected to produce only sweetness and light, not crank fumes.   Positive crankcase ventilation has been in use since the 1950s.

 

But if you don't want to recycle the fumes into the air intake (and I don't) a catch tank with a small filter on its vent will allow the worst of them to condense, and all you need to do is empty the rather yucky stuff out of the tank now and then.   There are all sizes available, with all sorts of wingdings attached from baffles to sight-tubes, at all sorts of prices, but good ones for less than £20.  See eBay!

 

JOhn

[68vitesse]

Do not understand this, if I remove the oil filler cap on my MK1 2L Vitesse it runs very badly if at all. Had same symptoms with a holed breather pipe and when the top came of the smiths emission valve.

 

Regards

 

Paul

[Pete Lewis]

Paul.   if you remove  filler caps   smiths valves or hole any  hose or part  of the sealed breather you allow air into the engine and  bypass the carburetors so negating any settings or idle control.

 

if you fit any of the suggested open breather ideas  you must plug the two suction spouts on the carb bodies or the tapping into the manifold depending on your cars designed set up.

Pete

[Red Devil]

I've clearly opened myself up for criticism here haven't I?! To be fair I wasn't aware of the consequences so will look into the solution you have mentioned.

 

To be honest when I got the car there was a short piece of pipe with a mini air filter on the end but as the car got up to temperature the running went all lumpy and then wouldn't start. Adding the long hose seemed to cure this. I'd be happy to install the original fittings/pipes but have assumed it would go back to running rough again although I don't know why given it was designed like this!

 

Will attempt to make myself less anti-social over the weekend!

 

Steve

[Pete Lewis]

Ha dont get fumming about this

 

1600 and early mk1 had open breathers so you got the pong from the crankcase vent and the gauze filtered filler cap.... I prefer steam loco pongs for nostalgia

 

guess there is some advantage in sealed , in that the vacuum saves some oil leakeage

 

pete