41 replies to this topic

[new_zealand _minis]

i have a non vented cheap aftermarket on that has been on my metro for ages .. the car has only done 40.000kms .. its mint never let me down. purrs .. but if you take off the cap when it is running it dies down and idles really low untill you put the cap back on

so that is not right saying no caps were made with no vent !!!

[midridge2]

http://www.minisport...ategory37_1.htm dan, do you just dream these things up? read what it says at the top of the page on the tmf website, if you dont know for sure, say this in your reply.

[liirge]

i have a non vented cheap aftermarket on that has been on my metro for ages .. the car has only done 40.000kms .. its mint never let me down. purrs .. but if you take off the cap when it is running it dies down and idles really low untill you put the cap back on

so that is not right saying no caps were made with no vent !!!

All A-series engines do this even ones with vents, the vent as mentioned previous is used to restrict air flow into the crank case NOT stop it. Opening the cap whilst running and your engine will do what you describe.

Edited by liirge, 12 September 2011 - 10:52 AM.

[liirge]

http://www.minisport...ategory37_1.htm dan, do you just dream these things up? read what it says at the top of the page on the tmf website, if you dont know for sure, say this in your reply.

But Dan was bang on...
In his first post he said that they changed from the breather to the vented oil filler cap with the built in restriction as to meter the control of the crankcase ventilation.....maybe you should read with more care..

Edited by liirge, 12 September 2011 - 10:55 AM.

[midridge2]

because you can't get any oil caps without a vent.

that is what dan said.

[liirge]

Well I think you are hard pushed to find them over here in the UK - seems a bit pedantic really for such a hard message.

Edited by liirge, 12 September 2011 - 01:26 PM.

[midridge2]

Really no oil cap you've ever owned is vented? that's odd....pretty sure Dan has already mentioned above that you cant get caps with out a vent in them.,,
as said by liirge,

so both roy and myself and new zealand minis all need to read with more care because "you cant get caps with out vent in them"
means you can get them but because they are listed in australia i am being pedantic.
well i just found them listed on miniamania in usa and thats after a quick search.

so the real question is can you get non vented oil filler caps as fitted to rocker covers with the breather pipe or were non vented oil filler caps never made for minis?

[Jack BRCG]

Is this a 998 or a 1275?

its a 1275 bored to 1293. but it i think its had the head skimmed many times and the block a few times to so it runs a realy high compresion, and i thought maybe this could lead to higher oil pressure?? not sure.
so i assumed adding a breather at the top end would lose a bit of that pressure, as well as the oil filler which does have the hole in.....

[liirge]

Really no oil cap you've ever owned is vented? that's odd....pretty sure Dan has already mentioned above that you cant get caps with out a vent in them.,,
as said by liirge,

so both roy and myself and new zealand minis all need to read with more care because "you cant get caps with out vent in them"
means you can get them but because they are listed in australia i am being pedantic.
well i just found them listed on miniamania in usa and thats after a quick search.

so the real question is can you get non vented oil filler caps as fitted to rocker covers with the breather pipe or were non vented oil filler caps never made for minis?

Be quiet you're not helping the initial question if you wish to argue further PM me, if you must

Is this a 998 or a 1275?

its a 1275 bored to 1293. but it i think its had the head skimmed many times and the block a few times to so it runs a realy high compresion, and i thought maybe this could lead to higher oil pressure?? not sure.
so i assumed adding a breather at the top end would lose a bit of that pressure, as well as the oil filler which does have the hole in.....

Right, what breathers do you have on at the moment?
in theory as long as your rings are in good condition the CR should not make a difference to your Crankcase pressure. When the engine is running and you remove the breather pipes, is there a lot of puffing out of the breathers? even oil itself, do you have both breathers? or just one?

[Jack BRCG]

just the two crankcase breathers atm. unless theres more i dont know of ha. the engine pressures are so high i blow head gaskets every 3 to 4 months, altho the metro turbo one seems to be lasting atm. theres just the normal amount coming out of the crank case, no oil tho.

[liirge]

How do you know the pressure?
Crankcase pressure wouldn't kill a head gasket.

are you talking about Oil pressure? as that is irrelevant to the breathers.

[Jack BRCG]

ah right. i duno then ha sorry im not the most knowledgeable. i think im gona leave it for now as im going on the rollers at the end of the month and the guy who runs it used to be big and downtown back in the day so im sure il get a good answer. shame its being rollered a few days after castle coombe tho ha

[midridge2]

Be quiet you're not helping the initial question if you wish to argue further PM me, if you must.

or you could just admit you were wrong, you told roy he was wrong and now you dont want to admit it on the forum.

[Jack BRCG]

by the way thanks for your help liirge.

[Dan]

i wanted to do it as i get oil leaks at high pressure. all gaskets have been checked and the crank case breathers have been cleaned out.

Are your breathers currently connected to the carb as they should be? If so then changing to an open vented system will only increase the pressure in the system and so increase oil leaks, if you wish to try adding a port into the rocker cover connected up to the other breathers as Roy (BMCEcosse) suggests then give it a go but I'm fairly certain it won't help much. I think Roy and myself were misunderstanding each other there slightly, we both frequently advocate the use of the proper closed loop PCV system but I think he may have been under the impression I was suggesting to ditch it and I briefly thought he was suggesting to make an open system. He suggests using a port into the rocker, I believe that doesn't leave enough draught through the rest of the engine to properly clear it out and that's a very minor difference really. As Lirge says, crankcase pressure and oil pressure are not really related. The oil system is closed off from the crankcase essentially, the breather system ventilates pressure that builds up in the crankcase as a result of heating, pumping and blow by and draws out the various noxious fumes that collect in there. I do apologise for not being more thorough and saying:
"You can't currently get a non vented rocker cap in the UK to my knowledge, even all the aftermarket ones are vented. It has after all been many decades since they were used as a standard part, and fitting a vented one to an older type of breather system even with the large flat breather valve fitted makes little difference to how it performs."

I will freely admit I didn't know you could get them in other countries, but don't think it's that relevant and I don't believe I ever claimed they were never fitted. I also don't believe I've ever claimed to be infallible, in fact quite the opposite. I regularly point out that I am not a qualified engineer, not a professional mechanic and am nothing more than a fairly experienced enthusiast trying to help people. I don't know what it is I've done to upset you Midridge and I'm fairly sure we've never met but it seems clear from recent threads and posts made with increasing frequency that you have some sort of deep seated personal problem with me. Whatever it is, would you like to discuss it by PM rather than constantly picking up on largely irrelevant minutia and diverting threads away from their topics?