Engine breathing and oil consumption.

Technical MGB discussion
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Charles Farran
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Forename: Charles
Surname: Farran
Location: Warwickshire

Re: Engine breathing and oil consumption.

Post by Charles Farran » Wed Apr 17, 2019 12:42 pm

Dave,
You seem to be sorting out your problems! As i am sure you know the condenser tends to work or not work & for the little expense worth substituting & then trying the car without changing anything else to establish if that component is causing the problem. Some years ago i had problems with the pigtail wire that had got freyed insulation that caused an issue. I assume your distributor cap is in good nick as well as the rotor arm?
I had a misfire some year's ago that occurred at hugher speeds that turned out to be one incorrect plug gap (too large) - thought i had checked & double checked these , but it was still wrong picked up by a neighbour who has siimilar tastes in old cars ! Very cheap to fix)!
Cheers, Charles
1980 Roadster

Dave Wheatley
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Forename: Dave
Surname: Wheatley
Location: SW Scotland

Re: Engine breathing and oil consumption.

Post by Dave Wheatley » Wed Apr 17, 2019 2:12 pm

Thanks Charles,

This morning car running ok.

Took air cleaners off to check balancing and noticed aluminium pieces between carbs and air cleaners upside down. Now replaced correctly and had to slow down tick over. Could this affect breathing?
1978 MGB GT
1931 Austin 7 RM
1955 Standard 10
1972 Ford Cortina
No modern!

User avatar
Charles Farran
Posts: 210
Joined: Fri Oct 31, 2014 11:08 am
Forename: Charles
Surname: Farran
Location: Warwickshire

Re: Engine breathing and oil consumption.

Post by Charles Farran » Wed Apr 17, 2019 3:57 pm

Dave,
The two spacers have to be the right way up with gaskets. The narrow gap holes should be at the top. If placed the wrong way round the carbs don't fu ction correctly.It does affect the breathing!
Cheers, Charles
1980 Roadster

Vic Butler
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Joined: Wed Dec 21, 2016 6:07 pm
Forename: Vic
Surname: Butler
Location: North West Hampshire

Re: Engine breathing and oil consumption.

Post by Vic Butler » Thu Apr 18, 2019 7:53 am

David, it would be interesting to see what happens now if you used the original breather system.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine

Dave Wheatley
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Forename: Dave
Surname: Wheatley
Location: SW Scotland

Re: Engine breathing and oil consumption.

Post by Dave Wheatley » Thu Apr 18, 2019 12:31 pm

Vic, i am boing to do that today.

Will report back.

Dave
1978 MGB GT
1931 Austin 7 RM
1955 Standard 10
1972 Ford Cortina
No modern!

Dave Wheatley
Posts: 122
Joined: Fri Sep 28, 2018 4:55 pm
Forename: Dave
Surname: Wheatley
Location: SW Scotland

Re: Engine breathing and oil consumption.

Post by Dave Wheatley » Thu Apr 18, 2019 6:10 pm

Well, reverting to original breathing still smokes a lot, so back to previous owners system for now. Distributor now got the earthing pigtail wire, and the original condensor appears to be OK.
New problem now though see new thread - oil pressure.
1978 MGB GT
1931 Austin 7 RM
1955 Standard 10
1972 Ford Cortina
No modern!

ChargedAutoGT
Posts: 33
Joined: Wed Nov 21, 2018 9:37 pm
Forename: Graham
Surname: Moore

Re: Engine breathing and oil consumption.

Post by ChargedAutoGT » Fri Apr 19, 2019 12:45 am

Dave
When you say open pipe to cloth filter- are you referring to one of those mini K&N type ones that sits on the top of the pipe. If so, i suspect your problem is as follows.

i am guessing your front tappet cover gauze has been removed. not uncommon as after a few decades without cleaning, they turn into a solid block.

So the original owner had crank fumes condensing at the cloth filter and running back into the sump via the tappet cover pipe.

But now, they are going into the carbs and being burned in the engine.

I would buy one of the MGB V8 flame traps. Also used on landrover.
https://www.ebay.co.uk/itm/251074429166 ... K:MEWAX:IT
if they are as they should be, they will contain a gauze.

add this into the pipe which you have re-routed to the Y piece and then the carbs. i think you will find it helps the fumes to condense and return to the sump unburned. position it close to the tappet cover so it's orientation promotes flow back to the engine.

I tried this one mine, it worked and my oil consumption went down from a pint every 150 miles to a pint every 650. I know for a fact my gauze is missing. i was advised at the time not to replace it. poor advice.

G

Dave Wheatley
Posts: 122
Joined: Fri Sep 28, 2018 4:55 pm
Forename: Dave
Surname: Wheatley
Location: SW Scotland

Re: Engine breathing and oil consumption.

Post by Dave Wheatley » Fri Apr 19, 2019 9:56 am

ChargedAutoGt. Thanks for that.

The 'filter' was simply a small piece of cloth tied over the end of the up pipe from the side cover plate.

When I blow down the open up pipe to the front side plate, there is absolutely nil resistance, so your comment about removal of the gauze and any crud makes sense.

Your oil consumption problem seems to replicate mine, so I have ordered the Flame trap set, and will report back after trials.

I don't fancy removing the front side plate, unless I have to!

The 'pipe to catch tank' system is actually working quite well at the moment.

D.
1978 MGB GT
1931 Austin 7 RM
1955 Standard 10
1972 Ford Cortina
No modern!

ChargedAutoGT
Posts: 33
Joined: Wed Nov 21, 2018 9:37 pm
Forename: Graham
Surname: Moore

Re: Engine breathing and oil consumption.

Post by ChargedAutoGT » Fri Apr 19, 2019 10:41 am

well i hope it works for you. attached is a pic of mine when i removed it some years ago. the pile of crud is just a fraction of what actually came out.
G(raham)
[attachment=0]crank breather.jpg[/attachment]
Attachments
crank breather.jpg

Dave Wheatley
Posts: 122
Joined: Fri Sep 28, 2018 4:55 pm
Forename: Dave
Surname: Wheatley
Location: SW Scotland

Re: Engine breathing and oil consumption.

Post by Dave Wheatley » Fri Apr 19, 2019 10:59 am

Wow!

D.
1978 MGB GT
1931 Austin 7 RM
1955 Standard 10
1972 Ford Cortina
No modern!

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