mk1-forum.net

Not sure if this is the correct place for this, but anyway............

How have you guys done your engine breathers for your racers, climbers, rally and trackday toys ??

Currently I'm running the standard breathers from the timing chain cover and the transfer gear case separately into each of the twin SU's I'm running. On track I think this gets overwhelmed as following tight corners I get a big puff of oil smoke out the exhaust.

Should I add another breather off the rocker cover and pipe all three to a catch tank somewhere ??
Does anyone plumb the vent from the catch tank back to the carbs somehow to promote some suction or just let it vent to atmosphere via a filter ??

I see some racers have huge diameter breather hoses (perhaps 1 inch diameter) from the transfer gear case to the rocker cover and out to a catch tank under the wing. Is that really necessary or will half inch do ?? These large size breathers seem to do away with the standard oil separators, so do you rely on the catch tank to de-aerate ??

Any advice, experience and pictures most welcome !!

Thanks in advance.

Phil.

Hi Phil,


I have all 3 breather pipes, running into a catch tank, and no connection from tank to carbs, or inlet manifold.

I only use the std breathers on rocker cover, transfer housing, and timing chain cover.

Jens Christian

1"???? Tiny stuff

http://home.online.no/~lyngset/71gt.cfm ... =&pExPic=0;

As the smoke comes after corners (closed throttle) what happens if you repeat similar conditions in a straight line? Could be worn valve guides?

The 'oil seperators' are flame traps in a closed breather system. Do not connect 'open' hoses directly to the manifold

We run a 1380 hillclimb car with two 3/4" breathers into a catch tank on the inner wing, this then has a vent pipe to a rear leg on the front subframe so fumes go under the car, not into the cabin.

Mike.

COOPERCO wrote:As the smoke comes after corners (closed throttle) what happens if you repeat similar conditions in a straight line? Could be worn valve guides?

The 'oil seperators' are flame traps in a closed breather system. Do not connect 'open' hoses directly to the manifold

We run a 1380 hillclimb car with two 3/4" breathers into a catch tank on the inner wing, this then has a vent pipe to a rear leg on the front subframe so fumes go under the car, not into the cabin.

Mike.

Hi Mike

Nothing happening on the straights, but then you'd be at wide-open throttle so little vac on the carb to draw any vapours out of the breathers, or have I misunderstood how it all works ??

Yep I understand the concept of the flame traps and the positioning of the ports on the carbs to only draw under vac. I'm currently using the standard type of breathers with the built-in flame traps, so nothing goes direct to the carb or inlet manifold.

I'm guessing by the placement of your vent pipe under the car you also benefit from some negative pressure draw at speed thus helping the engine "breath" when at wide-open throttle which you wouldn't get from the standard carb breather set-up.

Phil.

Vegard wrote:1"???? Tiny stuff

http://home.online.no/~lyngset/71gt.cfm ... =&pExPic=0;

Yeah, I'm thinking of the ones like on Swiftune's Apendix K racers etc. They must be at least 1", maybe more like 1.5"

Far be it for me to question Swiftune but is it really necessary to be that big ??

Phil.

No it isn't but stops 'em getting gunked up.

Hi,

1. standart breather, into the rocker cover, other side out of the rocker cover, catch tank.
2. other standart breather, catch tank. 12mm are enough.

A-series with g'box under like to breathe.... Big hose = less pressure.... so:

1" tube from flywheel housing into rocker-cover --- 1" -90degree outlet from rocercover and 1" tube to catchtank... Tried and tested setup as used by ..... errh everyone?

Add to that - if you're running an S-block: std size tube from tappetcover and into catch tank or better yet.
This setup will allow any oil being 'thrown up' from sump - to exit onto the rocker cover intead of the catchtank.

Sorry to dig up a old thread .
I was experiencing fumes in my car (exhaust was fine ) I have A+ in mk1 with a kn breather filter on flywheel housing and one on timing cover . So i am interested in all words of wisdom on this to improve the situation once I have got car running after its winter rebuild.

To recap : Route flywheel housing pipe into rocker cover and via a 90 degree outlet run pipe to catch tank with tank vent pipe down front frame rear leg .
Where does timing cover pipe go ? I take it the Swiftune tank has 1 inlet and a vent outlet , anyone got one ?

Thanks