Breather Valve Problem ?
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pvisseriii said:
Mk3 850s and early 750 engines dumped the oil that overcame the oil pressure relief valve into the timing chest through this hole.
Most 750 Commandos and all 850s except the Mk3 dumped the overpressure oil back into the inlet side of the oil pump through these holes.
To reduce the amount of oil going into the timing chest ; tap and plug the hole in the first picture, drill a new hole like in picture two, and make sure your engine case has the passage in picture three drilled. Most do but a few rare ones don't.
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hobot said:Before I did the Combat oil drain mod, I'd whipped up pre-Peel into oil lather to find most of her 14 total leak sites. Never saw foamed oil to matter anywhere.
But I don't understand why Combat excess oil can pile up since the way the breather mouth is configured, oil should just shoot up through the baffle into big hose and out top of oil tank. I see this on wet sump start up pump downs, why not more so on the fly?
Peel standard Combat and TS breather mount plus the three 1/2" vents seemed and a tank top Dreer-Krank PCV solved all rpm wet sump and air free oil return to tank, and oil leaks/weeps, mists, even in breather hose, white glove dry as a bone inside up to tach pegging rpm. Only difference I've not seen others mention, is the extra big plus extra 3rd hole to connect biggest volumes. I made 3rd hole up by barrel.
Steve,
Air is not moving out of an open breather- it is moving in and out. If you have enough blowby to keep the oil moving out of the cases up the breather you won't have enough compression left to make any power.
I plug all the holes between the timing chest and the crankcase except for one 1/4 inch hole down low to drain the oil. No holes-no pumping losses. Vent through a reed from the crankcase. Jim
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Jim,
Yer dead right, just after I'd posted that message I realised it would make it worse.
The Mk3 850 Norton manual states that the oil return was modified to feed back into the supply. I remember LAB pointing out that printing error, and I never got round to doing anything about it, 'if it aint broke don't fix it', well perhaps it is and it might be worth doing this winter.
I wonder if that factory mod had anything to do with changing the breathing ?
Thanks,
Cash
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Got ya on mostly nuliifying pressure waves than active pumping out of blow by.
Apparently more than one way to skin this breather cat. Mine to increase volume with so so sealing, slow closing Krank PCV. Yours to keep small volume but add more efficient reed check valve. Like your way better, duh, as valve don't have to show and no need to drill/weaken with case vents. I'm still newbie, didn't know of your option back in early 2000's, just that other reed valves didn't work out as hoped.
I'm leaving Trixie Combat factory to keep a toe hold on old Earth, Peel OIF must function at extreme angles in all axls plus not empty oil out upside down a long time till recovered and hopfully just rode away. So I figured an active evacuation with no free path to ambient venting is way to go for Peel.
Low moderate rpm is not much an issue for regular breathers if working right, its the hi rpm hi throttle states that can benefit form active evacuation. We are both doing that, you but mechanical pump, Peel by Benelli[sp] chimney sweeper.
Exhaust suckers can be tricky, as some only work at low speeds until exhaust back pressure builds up, others only work good when exhaust flow is fast and furious.
Some, maybe Peels work well as at any rpm. Most car size suckers have to use tiny .125" restrictor to limit liquid oil pulling out along with vapors. I'll valve Peels. Found a cute little 1/8" AN aircraft valve in dirt pile but cleaned up ok.
Peels Exhaust Eductor is complicated by temp probe and big O2 bung/sensor in path, don't know where to tap in the sucker pipe, before or after O2 probe or how far away or close up. I may have to put Peels one piece 2-1 header on Trix and experiment with taps while plugging error holes.
http://www.lotecinc.com/exhausts_5.htm
Peel has another issue that may prevent your reed location, alternator butts up close to the mag blanking plate so may not have room for a 90's hose fitting.
Apparently more than one way to skin this breather cat. Mine to increase volume with so so sealing, slow closing Krank PCV. Yours to keep small volume but add more efficient reed check valve. Like your way better, duh, as valve don't have to show and no need to drill/weaken with case vents. I'm still newbie, didn't know of your option back in early 2000's, just that other reed valves didn't work out as hoped.
I'm leaving Trixie Combat factory to keep a toe hold on old Earth, Peel OIF must function at extreme angles in all axls plus not empty oil out upside down a long time till recovered and hopfully just rode away. So I figured an active evacuation with no free path to ambient venting is way to go for Peel.
Low moderate rpm is not much an issue for regular breathers if working right, its the hi rpm hi throttle states that can benefit form active evacuation. We are both doing that, you but mechanical pump, Peel by Benelli[sp] chimney sweeper.
Exhaust suckers can be tricky, as some only work at low speeds until exhaust back pressure builds up, others only work good when exhaust flow is fast and furious.
Some, maybe Peels work well as at any rpm. Most car size suckers have to use tiny .125" restrictor to limit liquid oil pulling out along with vapors. I'll valve Peels. Found a cute little 1/8" AN aircraft valve in dirt pile but cleaned up ok.
Peels Exhaust Eductor is complicated by temp probe and big O2 bung/sensor in path, don't know where to tap in the sucker pipe, before or after O2 probe or how far away or close up. I may have to put Peels one piece 2-1 header on Trix and experiment with taps while plugging error holes.
http://www.lotecinc.com/exhausts_5.htm
Peel has another issue that may prevent your reed location, alternator butts up close to the mag blanking plate so may not have room for a 90's hose fitting.
That was the theory of old, that Combat engines returned more oil up the breather than the pump return.
Now I understand, that's a better explanation than I've seen before. I just could not get my head around oil NOT finding it's way into timing chest and at least some going up the breather.
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So if you fit a reedvalve breather, externaly, would it be a worthwhile idea to fit a pipe like LUDWIG'S ,minus the breather,blocking off one hole, with the breather pipe, and getting it breathing from the crankcase, and if so would it need a baffle over the end to stop oil getting throwen up the pipe or would that make no difference.
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Fred's modification works if you are using the brake booster valve or other inefficient check valve. They don't react fast like a reed valve so they don't create much of a vacuum in the cases beyond idle. It is a good simple mod that has it's benefits. The biggest drawback I found was the short life of the brake booster valve.
When you install a reed valve up close to the engine where it really works to create a vacuum, it needs to breath from the crankcase. I have not seen a need to shield it from oil. I have not found that a little oil flowing out the breather hose and back to the tank causes a problem. Jim
When you install a reed valve up close to the engine where it really works to create a vacuum, it needs to breath from the crankcase. I have not seen a need to shield it from oil. I have not found that a little oil flowing out the breather hose and back to the tank causes a problem. Jim
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