In Australia, pre pollution control Minis had either of the two carburetor types you described. Pollution control Minis had an inlet pipe on the rocker cover with a small control hole and sealed oil filler cap. The fresh air was drawn from the charcoal canister where it was filtered as well as drawing in the petrol vapors collected from the carburetor vent and fuel tank vent. This is the best venting for a smell free drive. I'm so glad you talked about this. It seems most people's attitude is, "pollution control, rip it off it'll go better". As you pointed out. No, it doesn't.
In Australia we had vent from the top of the rocker cover with a short hose to the air box/side of carb and a tube out of the lifter cover at the back of the engine. I assume our oil caps were meant to have the filter, but I’ve never owned a mini with it in the cap. All of mine were just hollow.
Thank you for the very informative video. In my case I have an engine with blow-by. Would it be wise to connect the breather hose to the carburetor as I have it going to a catch tank? Many thanks to AC Dodd for introducing you through the live sessions!
I have the full breather setup on my 1275 Metro engine, but I am still being asphyxiated by fumes. Especially when I open a window. Definitely a fuel/fume smell. No fuel leaks found anywhere.
Question: I have a '94 SPI mini that's back to twin SU carbs now. Runs great. Stinky (fuel smell) though! I have the venting of the main crankcase breather going back to the carbs as you have. I THINK though a lot of the stink is the float bowls of the SU carbs venting to air. What I've done is connected the two carb float bowls vents together then teed off to the carbon filter under the wing along with the fuel return vent line which was already going to it. Seems to cut the stink in the cabin a fair bit. Does this make sense to you? Thoughts on this as a solution to the stink/venting? There is NOT a return line (or valve of any kind) from the carbon filter on my car though going back to the carbs to burn off any vapour stink that builds up in there. Do you think I could put a return line teed into the crankcase breather that feeds to the carbs to reburn vent gases that would pull more and more vacuum on the charcoal cannister as the RPMS get higher? Does this make sense how I've outlined it?
No you can't connect the canister to the breather port. The canister was supposed to be operated with a solenoid controlled by the ECU. Can try connecting it to the air filter housing. It may draw the fumes out.
@darrensrestorations991 Thank you for this timely video, very much appreciated. Question though. The breather from the tappet cover on the back of the engine, which you show going to the carb, you also mentioned that it sometimes goes to the air filter housing on earlier cars (what year is earlier?). Like the mini you showed at the very start and the very end, the black air filter housing around the carb, the port on the right side of the air filter housing is open. Is that supposed to go somewhere or should it be open? My mini is a 1978 Morris 1000cc, and the only breather it has is on the tappet cover. It has nothing on the chain timing cover and nothing on the transfer case. So just trying to work out where mine should go (I am rebuilding my mini, brought it not running). So I simply do the tappet cover breather to the carb, or does it go to the intake manifold? Just curious as yours shows the air filter housing port open, and I have seen that alot on google images, and I cant work out what should be on that... Thanks
The tappet breather should go to the carb. The port on the black plastic filter housing is not open. The early filter housings made of metal have an open fitting.
@@darrensrestorations991 ah you are right, the port on the black plastic is open on one cover I have, but not on the other. I think the open one is however not factory done. Wonder what this is for.... Thanks
Evening Darren, caught parts of the live stream last night and wanted to ask more about PCV & breathers. I have a 1310 A+ engine almost fully rebuilt with a wrath of new parts, one being a MED belt timing cover (which doesn't have the breather) I had planned on using the fuel pump hole and transfer case and pipe these back to Carb but then heard talk about oil being pushed up the pipe (which I didn't foresee) How do I best proceed? Will the transfer case breather provide enough pressure relief to be ok back to the carb or do I need to go back to a catch pot? This is a fast road build and now understand a timing belt minus the breather may not have been the best idea (hindsight 😅) Any help would be greatly appreciated? Understand with a new build there won't be as much blow by the pistons but am I walking into a bit of a problem.
Not really a problem as there are a few options. The fuel pump hole needs a baffle as mention on the stream. Can also use a valve cover with a breather pipe.
@darrensrestorations991 what sort of baffle would you recommend? I've seen the minimania one, but not any others. So if I baffled this vent from the fuel pump, would it still be best to pipe to carb or to a catch pot?
Always run to the carb. A baffle of similar size to the factory ones is needed. I suggest getting a vented valve cover as this would be the easiest way to add the second vent. Plus the valve covers have a baffle built into them.
@@darrensrestorations991 Thanks Darren, I've found a MK1/2 vented rocker cover on eBay with the internal baffle. Just to confirm, run the transfer case breather and rocker cover vent both back to carb and blank off the fuel pump hole I was going to use? Appreciate the help, loving your videos - great content and different from the normal videos that others put on YT 👍👍
Why would you or the engine want dirty oil soaked air being fed to it? Answer it doesn’t infact it’s bad for the engine performance! The crankcase pressure was only fitted back to the intake for emissions reasons nothing else, so what I do is after the oil catching box go straight down to the outside of the engine, jobs a good un job done simples 😃
Thanks for that great information.
I’m learning lots after watching yours & AC’s videos.
Keep them coming
Thanks, will do!
Thanks for that. I don't see much discussion on A Series engine breathers so this makes a nice change.
Yes I have come to realize that no one talks about them. Which is why I find so many disconnected. Hopefully my info will help a few new owners
In Australia, pre pollution control Minis had either of the two carburetor types you described. Pollution control Minis had an inlet pipe on the rocker cover with a small control hole and sealed oil filler cap. The fresh air was drawn from the charcoal canister where it was filtered as well as drawing in the petrol vapors collected from the carburetor vent and fuel tank vent. This is the best venting for a smell free drive. I'm so glad you talked about this. It seems most people's attitude is, "pollution control, rip it off it'll go better". As you pointed out. No, it doesn't.
Yep, exactly my thoughts. Controlling the fumes makes the driving experience so much nicer and no change in performance.
Very informative thank you
Glad it was helpful. Thanks for watching
Thanks........ useful information there. 👍
Thanks for watching.
Great information !
Glad it was helpful!
In Australia we had vent from the top of the rocker cover with a short hose to the air box/side of carb and a tube out of the lifter cover at the back of the engine. I assume our oil caps were meant to have the filter, but I’ve never owned a mini with it in the cap. All of mine were just hollow.
In that design, the engine vacuum isn't as strong and it doesn't need the filter as the fumes are being pulled into the air filter itself.
Thank you for the very informative video. In my case I have an engine with blow-by. Would it be wise to connect the breather hose to the carburetor as I have it going to a catch tank? Many thanks to AC Dodd for introducing you through the live sessions!
Yes, you can have it hooked up to the carb even with blowby.
Just be aware that it will change the air/fuel mixture when you do.
Thanks for the great information! Question though: when connecting the breathers back to the carb will this affect the mixture setting of the engine?
Yes it will change the mixture as the breather system will let more air/oily fumes into the carb.
@@darrensrestorations991 great thank you, that‘s good to know
I have the full breather setup on my 1275 Metro engine, but I am still being asphyxiated by fumes. Especially when I open a window. Definitely a fuel/fume smell. No fuel leaks found anywhere.
Then start checking for exhaust leaks. Also time for a proper tune.
Question: I have a '94 SPI mini that's back to twin SU carbs now. Runs great. Stinky (fuel smell) though! I have the venting of the main crankcase breather going back to the carbs as you have. I THINK though a lot of the stink is the float bowls of the SU carbs venting to air. What I've done is connected the two carb float bowls vents together then teed off to the carbon filter under the wing along with the fuel return vent line which was already going to it. Seems to cut the stink in the cabin a fair bit. Does this make sense to you? Thoughts on this as a solution to the stink/venting? There is NOT a return line (or valve of any kind) from the carbon filter on my car though going back to the carbs to burn off any vapour stink that builds up in there. Do you think I could put a return line teed into the crankcase breather that feeds to the carbs to reburn vent gases that would pull more and more vacuum on the charcoal cannister as the RPMS get higher? Does this make sense how I've outlined it?
No you can't connect the canister to the breather port. The canister was supposed to be operated with a solenoid controlled by the ECU.
Can try connecting it to the air filter housing. It may draw the fumes out.
@darrensrestorations991 Thank you for this timely video, very much appreciated. Question though. The breather from the tappet cover on the back of the engine, which you show going to the carb, you also mentioned that it sometimes goes to the air filter housing on earlier cars (what year is earlier?). Like the mini you showed at the very start and the very end, the black air filter housing around the carb, the port on the right side of the air filter housing is open. Is that supposed to go somewhere or should it be open? My mini is a 1978 Morris 1000cc, and the only breather it has is on the tappet cover. It has nothing on the chain timing cover and nothing on the transfer case. So just trying to work out where mine should go (I am rebuilding my mini, brought it not running). So I simply do the tappet cover breather to the carb, or does it go to the intake manifold? Just curious as yours shows the air filter housing port open, and I have seen that alot on google images, and I cant work out what should be on that... Thanks
The tappet breather should go to the carb. The port on the black plastic filter housing is not open.
The early filter housings made of metal have an open fitting.
@@darrensrestorations991 ah you are right, the port on the black plastic is open on one cover I have, but not on the other. I think the open one is however not factory done. Wonder what this is for.... Thanks
What about twin SU carbs with pancake air filters and no where to plug the breather hose too ?
The factory air filter housing had a breather port. Also some twin manifolds have fittings for the PCV valve
Evening Darren, caught parts of the live stream last night and wanted to ask more about PCV & breathers. I have a 1310 A+ engine almost fully rebuilt with a wrath of new parts, one being a MED belt timing cover (which doesn't have the breather) I had planned on using the fuel pump hole and transfer case and pipe these back to Carb but then heard talk about oil being pushed up the pipe (which I didn't foresee) How do I best proceed? Will the transfer case breather provide enough pressure relief to be ok back to the carb or do I need to go back to a catch pot?
This is a fast road build and now understand a timing belt minus the breather may not have been the best idea (hindsight 😅) Any help would be greatly appreciated? Understand with a new build there won't be as much blow by the pistons but am I walking into a bit of a problem.
Not really a problem as there are a few options. The fuel pump hole needs a baffle as mention on the stream. Can also use a valve cover with a breather pipe.
@darrensrestorations991 what sort of baffle would you recommend? I've seen the minimania one, but not any others.
So if I baffled this vent from the fuel pump, would it still be best to pipe to carb or to a catch pot?
Always run to the carb.
A baffle of similar size to the factory ones is needed.
I suggest getting a vented valve cover as this would be the easiest way to add the second vent. Plus the valve covers have a baffle built into them.
@@darrensrestorations991 Thanks Darren, I've found a MK1/2 vented rocker cover on eBay with the internal baffle.
Just to confirm, run the transfer case breather and rocker cover vent both back to carb and blank off the fuel pump hole I was going to use?
Appreciate the help, loving your videos - great content and different from the normal videos that others put on YT 👍👍
@danhardy5752 yes run both to the carb and blank off the fuel pump hole.
Thanks for watching!
when wouldnt you run the breather system?
On a race car where oil changes are frequent and emissions are meaningless.
@@darrensrestorations991 and you will then have to run an oil catch can (in most cases)
Why would you or the engine want dirty oil soaked air being fed to it? Answer it doesn’t infact it’s bad for the engine performance! The crankcase pressure was only fitted back to the intake for emissions reasons nothing else, so what I do is after the oil catching box go straight down to the outside of the engine, jobs a good un job done simples 😃
It doesn't change the performance of the motor any significant amount.