Big Block head Breather lines

[1down5up]

Looking for the collective wisdom/opinions.

The early big blocks loops didn't have the breathers lines from the valve covers, I believe they appeared with the tonti frame bikes.

I can't imagine they do anything for crank case pressure with the big Breather hole in the back of the case, and I can imagine they breath buch considering its only going though a banjo bolt.

I'm sure they put them in for a reason, but I can't quite see it.....

Asking as I am on my 3rd set of Breather lines that keep coming apart at the crimp on my 850 Lemans, and thinking of just blocking them with a bolt in the valve cover.

[Guzzistajohn]

You can get a braided steel version. My CX has had 'em for years

[guzzista]

 

You can get a braided steel version. My CX has had 'em for years

  Oil feed lines from block to heads can be had in stainless coated teflon. Breather hoses are either smooth rubber or fabric wrapped rubber ( round heads Tontis). You can reuse the banjos and use better quality rubber hose purchased by the foot and  save  some $ ( Guzzi content)

[jacksonracingcomau]

Looking for the collective wisdom/opinions.

The early big blocks loops didn't have the breathers lines from the valve covers, I believe they appeared with the tonti frame bikes.

I can't imagine they do anything for crank case pressure with the big Breather hole in the back of the case, and I can imagine they breath buch considering its only going though a banjo bolt.

I'm sure they put them in for a reason, but I can't quite see it.....

Asking as I am on my 3rd set of Breather lines that keep coming apart at the crimp on my 850 Lemans, and thinking of just blocking them with a bolt in the valve cover.

One of those things that had me for years, why ?
So a few years ago I built the luddite cali 1100 engine, with cam, gears, twinplugs, points and carbs
I went for v700 box without rocker breathers and rocker covers no vents.
Orig breathers in head became rocker feed cos of inner plugs.
Oil return line as yours, behind clutch
Never blown a drop of oil, no leaks
Except when flapper valve stuck (got removed pdq, but first time it actually happened on my bike)
And an oil leak from o ring on my cam sensor removal plate
Araldite fixed that, forever.

50 odd thousand miles now, nothing else broken, nor had to come apart at all, hammered always, ridden as designed

So categorically I can sayI have no use for rocker breathers at all, will remove them from all of mine
That there can be no mayo, the icing on the cake

[blackcat]

Except when flapper valve stuck (got removed pdq, but first time it actually happened on my bike)

Is it absolutely necessary to have the flapper valve? My CX has been doing some weird breathing things, I looked at the check valve and it’s fine and I considered the Agostini breather box but I don’t want to spend $140 bucks for a non-racing bike.

[jacksonracingcomau]

Is it absolutely necessary to have the flapper valve? My CX has been doing some weird breathing things, I looked at the check valve and it’s fine and I considered the Agostini breather box but I don’t want to spend $140 bucks for a non-racing bike.

No, break out flapper valve. POS, keep pcv, or better, use new late model one, with circlip,
All will be good

[jwinwi]

The lines attached to the valve covers are to vent water vapor. They appeared on the Tonti-framed round fin big twins but were eliminated when the square fin motors arrived so maybe they were not very effective or necessary.

Edit: LM3, Cal2, T5, SP2 and Sport 1100 do not have water vapor vents but all other square fin motors DO have vents at the top of the cylinder head.

[blackcat]

No, break out flapper valve. POS, keep pcv, or better, use new late model one, with circlip,
All will be good

I eliminated the valve in the breather, it is still rattling around in the box, but what about the stock valve on the engine? I have read that some people remove them too but they were talking about racing applications with the Ago breather.

[wirespokes]

Orig breathers in head became rocker feed cos of inner plugs.

Could you explain? I'm not following when you say they became rocker feed. Not familiar with the inner plugs either.

My 85 LM4 has the head breather tubes. The breather hoses were all hard and rotted when I got the bike so mounted a ford pinto PCV valve at the engine and ran a hose to the forward attachment point on the backbone. Then I ran a hose from the right head to the left. It's not blowing any oil, so guess it's working. Seems I could plug the holes in the head, but wonder what you did with them instead.

[Frenchfrog]

Jackson...I'm a bit dense ....why would you eliminate the valve in the breather box or does having that and the ball valve allow higher crankcase pressures than good? I'm running both currently and to be honest am a bit lazy ...so convince me to get my finger out and disable it !!!

[Rick4003]

Could you explain? I'm not following when you say they became rocker feed. Not familiar with the inner plugs either.

To have space for the inner plug it is common to move the rocker oil feed to the breather pipe position, as the standard feed runs right were you would like to have your spark plug. The original feed hole is blocked in some way and a new passage is drilled from the breather hole to the rocker oil feed.

[wirespokes]

Thanks, Rick! I didn't get that it was for a dual plug conversion. Thanks for the explanation.

So when the second plug is installed, the head breather goes away with no ill effects. And since the newer bikes don't have it, plugging is a good option. I'll have to check into removing it totally.

[jacksonracingcomau]

To have space for the inner plug it is common to move the rocker oil feed to the breather pipe position, as the standard feed runs right were you would like to have your spark plug. The original feed hole is blocked in some way and a new passage is drilled from the breather hole to the rocker oil feed.

This, weld the orig feed, drill for new

Jackson...I'm a bit dense ....why would you eliminate the valve in the breather box or does having that and the ball valve allow higher crankcase pressures than good? I'm running both currently and to be honest am a bit lazy ...so convince me to get my finger out and disable it !!!

They both do same job, flapper stuck shut on mine, not that unusual but first time for me, my orig lm box still virgin.
So not really for a gain but removing flapper can do no harm
Early pcv’s could  stick too, post mid 80’s have circlip, have never had problem with them.
But oil return must be under oil level, that one caught me out.
Spiney style drains to sump plug an easy mod for frame breathers, after blocking rocker / head breathers.

[Stevex]

Those breather lines are just mayo traps.
On my LM2 I've removed them, blanked the valve covers and turned them around, also blanked off the crank breather valve where the head breathers used to enter.

[Frenchfrog]

Thanks jackson...would you go to the trouble of getting the breather out and getting rid of the flapper???It does seem that I'm getting slight weepage from somewhere in the clutch after a complete rebuild and seal and it does seem to be engine oil...I did the epoxy on the cam plug trick and all the other recommendations, fresh seals obviously...wonderi ng if this "flapper " working might  mean too much resistance to crank venting ?
 

[jacksonracingcomau]

Thanks jackson...would you go to the trouble of getting the breather out and getting rid of the flapper???It does seem that I'm getting slight weepage from somewhere in the clutch after a complete rebuild and seal and it does seem to be engine oil...I did the epoxy on the cam plug trick and all the other recommendations, fresh seals obviously...wonderi ng if this "flapper " working might  mean too much resistance to crank venting ?

Would be a very long shot, when they stick, the symptom is oil chucked from vent pipe, pressurised cases send oil up the return pipe and with nowhere else to go it jumps ship.
Two of my 3 big blocks still have the flapper AND PCV, both with ludicrously high mileage and no problem.
Of course all came with both and most have survived without the issue
The one that failed was a nos orig v700 one, less than a year in use but possibly actually made in 60’s.

Prob more to be gained by getting rid of rocker breathers on both my others but neither of them make mayo so no pressing issue for me. A “one day” job in a list of many, probably when apart for something else
Can’t hurt to deflapper and derocker vent yours, fixes two potential issues but unlikely to fix your leak

UNLESS
Leak is at connection to breather box and draining behind clutch, wouldn’t be first time for that one.

SO
In your case I probably would but be prepared for another crab if leak stays.
The only sure fire test is bell housing full of water and (15psi max ) compressed air in hot cases.
Game is to strip as much as possible, then run to working temp, quickly pull motor, nose in car tyres, air in through breather vent, other hoses plugged, look for west ham theme song.

[Antietam Classic Cycle]

Jackson...I'm a bit dense ....why would you eliminate the valve in the breather box or does having that and the ball valve allow higher crankcase pressures than good? I'm running both currently and to be honest am a bit lazy ...so convince me to get my finger out and disable it !!!

You don't want to do that. One or the other, but not both. In my experience, they can counteract one another and cause crankcase presurrization.

[Frenchfrog]

Thanks for the advice from both of you.....I will get the breather box and disable it soon !!

[brider]

The lines attached to the valve covers are to vent water vapor. They appeared on the Tonti-framed round fin big twins but were eliminated when the square fin motors arrived so maybe they were not very effective or necessary.

Edit: LM3, Cal2, T5, SP2 and Sport 1100 do not have water vapor vents but all other square fin motors DO have vents at the top of the cylinder head.

My Cal 2 square-fin with NO valve cover breathers suffers from mayo, I find it whenever I take the covers off to adjust valves, and it POs me to no end that there are no vents. Mayo traps? I suppose, if they are too small diameter, but I'd rather have them as an ATTEMPT to vent the covers than no vents at all.

[jacksonracingcomau]

My Cal 2 square-fin with NO valve cover breathers suffers from mayo, I find it whenever I take the covers off to adjust valves, and it POs me to no end that there are no vents. Mayo traps? I suppose, if they are too small diameter, but I'd rather have them as an ATTEMPT to vent the covers than no vents at all.
[/quote

Easy to add if you want to, opposite logic to mine.
Much written on here, search for pages and pages of mayo talk

[1down5up]

Thanks for all the input, I think I will just block them off with some stainless bolts, and plug the corosponding vents on the Breather box.