Can any one explain how this works and what the vent path to atmosphere is supposed to be? I had a wet sump situation on a new purchase and fully expected oil to be ejected from the breather hole at the end of the cam . Nothing came out.
This is one of those areas that we just have to take on faith.....it would seem the logic behind this cork nightmare was only known to Hopwood . I've had a couple people try and explain this to me but my BS detector was blaring , I suspect they were simply using big words to make me "think" they knew????
Anyway , seriously , I think I have a couple of bottom ends open on the shelf , I'll take a closer look , if anything I'll see if the cams are hollow ?I seem to recall they had a timed disk but it only had one hole ,and I seem to recall seeing a few of them with the driving tabs broken , I could be completely wrong...it's been a while and me memory is shorter than my .....what were we talkin' about??
Your A10 crankcase is supposed to vent excess pressure/vapor/blow-by via the timed breather on the end of your camshaft gear and discharges out of the left hand crank case on the drive side. When the pistons are on their downstroke the hole in the timed breather should be lined up with the gallery in the inner timing case which allows the release of the excess pressure. This gallery continues through both crank case halves and vents to atmosphere out of the left hand crankcase on the drive side just behind the primary chain case. The exit hole is just below the camshaft blind bush area of the case. Stick your finger down there and you'll feel the hole. Some A10/A7's had a nipple there at the exit to attach a pipe/hose.
Ok guys, cam is definitely not hollow, nor does it have the later disc and driving tang set up. Salty dog-good answer thanks-I cabn see that the timing case and crankcase get connected with the timed breather- still do not quite follow how the port to atmosphere is opened/closed?, cam is solid running in a solid bush. Is there a drilling/port that is opened and closed somehow? Rob
Rob , I took a quick look and it sorta came back to me , completely different arrangement than an A-65.This is sorta complicated to try and describe but I'll try . First there is a cross drilled passage that is blanked off in the inner timing cover below the magneto. this connects to another passage in the crankcases through a manifold in the top of the inner timing cover and eventually is dumped to the atmosphere sorta under the cam on the left side case .The timing seems to be achieved by the cam position.The cam drives a sorta top hat shaped piece that rides in the inner timing cover,they are keyed together so that a pair of cross drilled holes align with the drilling in the cover at the bottom of the stroke (or wherever they set it ?) allowing crank pressure to be ducted away at a certain point and the undrilled surface of this tophat piece block the passage at all other rotation.I've heard that the thickness of the cork is the key to getting this right .
BTW, just consulted the olde Haynes manual and there are some pics and a description of assembly procedure . They strongly advise to replace the cork with proper thickness to insure no endplay in the breather.Also a small cutaway drawing of the breather setup in the Bacon twin resto book on page 57.
OK guys, have discovered that there is a drill way located under the cam lube trough . It runs parallel with the cam and joins up the timed breather with the verical vent to atmosphere located on the drive side also below the cam.So pressure passes into the timing case then through the port in the timed breather , down this drillway to atmosphere.A poor fit on the cork seal will not only give to much end play ,it will also reduce the breather efficiency. Going to try it all again ! many thanks Rob
Rob, The breather route is through a drilling, below the bolt hole, in the lug in the crankcase mouth. The drilling below the camshaft is for oil from the relief valve which sprays onto the cam. There is also another drilling behind the timing gears from this gallery.