Breathers, can anyone help.

greg brillus

greg brillus

Well Known and Active Forum User
VOC Member
I had pondered on this topic whilst building the racer....In the end I just used the original timed breather, but enlarged the outlet pipe and ALL associated fittings to 3/8 bore, and fed it into the kickstarter cover. After the National titles a few weeks back it had put no more than a table spoon of oil/ water into the bottom, which I suck out with a piece of clear tube. There is more to the story, but it seems to work fine for me, as they said, nice round and true bores with correctly sealing rings is the answer. Cheers..........Greg.
 
T

timetraveller

Well Known and Active Forum User
VOC Member
They were not extra breathers. They were replacements for the timed breather which was not fitted and the outlet hole not machined out. Only one 'D' type breather was fitted to each engine but minor changes were made to the top valve guide seat in order to let the air flow more freely past the rocker bushes, past the top valve guide, the valve spring and out of the banjo bolt which interfaced to the breather tube.
 
P

peterg

Well Known and Active Forum User
Non-VOC Member
Howdy highbury,

To scale this unit, the body is 3/4 inch dia, the inlet nipple 1/2 inch, it is 1 3/4 inches long where it portudes from the valve inspection cap to the end of the nipple and the hose I have fitted is of 365 thou inner diameter. That hose of the same exterior appearance as the other fuel/oil lines and sourced from John Healey over here and these lines made to look somewhat original. This hose run is made as short as possible to exit point to minimize the effects of pressure drop on these lightly springed shuttle valves as restrictions on either side alter their performance.
 
L

len.c

Well Known and Active Forum User
Non-VOC Member
This thread is really interesting and just in time as I am trying to improve the heavy breathing my mate suffers from, ( his twin ) not himself as far as I know. I was tempted to ask about using both the D and the C breathers in conjunction but having read the suggestions I have some questions answered . I do like the idea of going ahead with using both but installing a a blow not suck valve on the D type, this engine has not bedded in yet after new barrels pistons etc my advice to anyone undertaking this type of rebuild would be seek out a reliable machinist who can do a proper matching job between pistons and barrels, or better still talk to Clev Trev
 
Top