Breather with twin carbs

[mattd1984]

Has anyone that is running twin carbs connected the breather tube from the oil filler neck to the top of the carbs?

Im interested as either going to fit a breather box or do this?

 

[easy]

What carbs are they dood?

 

[mattd1984]

Webber ict 34's

 

[Tezzah]

Yes, I have.


Sent from my 32Gb iPhone 4 using Tapatalk from the hell that is work.

 

[dubdubz]

breather box is a bit overkill, but it is best to T and vent both, as the carbs do benefit from the oily fumes - apparently it helps lube the valves or something in the head? sure that's what Laurie Petitt said in a post once?

 

[mattd1984]

Cheers so if you have done it have you just cut a hole in the top of the filter and run it to there? Just one of the carbs?

 

[dubdubz]

I haven't done these carbs yet but you can get a right angle barb fitting that you drill a hole that they fit into........ I did a T on mine so both carbs got the pressure

 

[Loxy]

Cheers so if you have done it have you just cut a hole in the top of the filter and run it to there? Just one of the carbs?

When i fitted my drlas I tapped holes in the tops of the filters and put a barb in the right hand one for the oil breather and another in the left hand one for the fuel tank breather.

 

[sparkywig]

 

[skin69]

I was warned that some barbed connectors can be restrictive as they've got verry narrow holes in them.
I ended up getting some 15mm copper pipe (plumbing) fittlins from a DIY shop, they work a treat and only cost pennies...

 

[mattd1984]

Ok cool, so best to tap into the top of the filters then and leave the rocker covers alone? Just a little worried the oil may gunk up the carbs but im sure im worrying about nothing as dont think there would actually be that much oil.

 

[sparkywig]

The oil vapour, if any, condenses in the breather box and then dribbles back down into the oil filler.

 

[mattd1984]

Ok cool, ill go for that rather than the rocker covers.

Now just to decide on the bugpack or the cb tower breather? What you think?

 

[Dirty Harry]

Ok cool, ill go for that rather than the rocker covers.

Now just to decide on the bugpack or the cb tower breather? What you think?

Go for the CB tower is has a larger volume (important) and looks better, just my 2 cents.

 

[six]

sparkywig what is your setup doing? are there 3 pipes? 1 is the drain to the oil filler, 2 from the carbs?

for the dumb (me) could you explain I have no idea how they work, but ti think maybe i should get one

 

[Zcat7]

I've been working a lot on crankcase breathing since fitting my twin Solex carbs as I started to get some oil blowby at the stock filler neck. I have a breather box the same as Sparkywig's but the one thing I don't understand is how the oil doesn't dribble out from the lid? My version of this box is designed to be mounted with the logo facing upwards as the lid is not sealed to allow it to breath. Did you grind the little pedestals off and seal it then rely on the carbs to draw the vapour out?

My setup didn't start to work effectively until I ditched the mech fuel pump and installed a crankcase breather there. It's lead me to think that my stock breather is blocked... I now have vents in both rocker covers, the stock outlet and the fuel pump outlet.

All seems to be OK now performance/leak wise but I do fid that I get some faint oily smells when driving hard, I guess because ultimately I am still venting into the fresh air side of the engine bay through the breather box. I'm considering running a pipe to each carb to draw the fumes away.

Regarding the CB Tower/breather - I saw some reports that this could be troublesome for filling depending on pipe configuration, in that there are 2 pipes at the bottom of the tower (I guess to run into the rocker covers) that are lower than the oil fill neck. Basically oil will start to flow into the rocker covers before it reaches the filler neck. If you block off these 2 pipes you will get a little sump of oil there.

http://www.thesamba.com/vw/forum/vi...postorder=asc&highlight=oil+breather&start=20

Neil

 

[sparkywig]

I've been working a lot on crankcase breathing since fitting my twin Solex carbs as I started to get some oil blowby at the stock filler neck. I have a breather box the same as Sparkywig's but the one thing I don't understand is how the oil doesn't dribble out from the lid? My version of this box is designed to be mounted with the logo facing upwards as the lid is not sealed to allow it to breath. Did you grind the little pedestals off and seal it then rely on the carbs to draw the vapour out?

No, works fine with no leaks.

My setup didn't start to work effectively until I ditched the mech fuel pump and installed a crankcase breather there. It's lead me to think that my stock breather is blocked... I now have vents in both rocker covers, the stock outlet and the fuel pump outlet.

All seems to be OK now performance/leak wise but I do fid that I get some faint oily smells when driving hard, I guess because ultimately I am still venting into the fresh air side of the engine bay through the breather box. I'm considering running a pipe to each carb to draw the fumes away.

Because you're not venting back into the carbs/air filter, so causing positive pressure in the crankcase.


Neil

sparkywig what is your setup doing? are there 3 pipes? 1 is the drain to the oil filler, 2 from the carbs?

for the dumb (me) could you explain I have no idea how they work, but ti think maybe i should get one

The reason why I've fitted a breather box was that I'd replaced the stock oil filler/breather. The breather system works on creating negative pressure in the crankcase, as stock, so that you don't pressurise the case causing oil leaks or oil blowby.
Yes, 3 pipes. 1 from the oil filler neck that takes any vapour into the breather box where the oil condenses and runs back down into the filler neck, and the other 2 take any fumes back into the engine to be burnt in the combustion process.

 

[Zcat7]

Looks like your's breather box must be a different type to mine, though I confess I have considered sealing the lid to promote some negative pressure when I reconnect to the carbs.

Apparently some leaks through increased backpressure are common when fitting twin carbs as the stock breather system is borderline for a 1600 engine (being basically the same as for a 1200 unit). The extra power produced will unsuprisingly cause more piston blow-by and the whole unit revs so much more freely with the short inlet manifolds causing extra "pumping" in the crankcase.

Feeding only the stock breather outlet into one air filter wasn't enough for my setup hence the tweaking I've been doing (although as I said earlier I now suspect my stock breather is partially blocked...).
The other problem of course is that the aftermarket breather fittings from most VW stockists tend to be 12mm OD and with a narrow bore (maybe 9mm?) whereas stock is 17mm OD (I think), so you have to be careful to ensure you don't end up with a smaller bore than stock when swapping to some aftermarket parts...

Neil