17 replies to this topic

[minibarnerz]

I think i have an air leak in my intake and put it down to my inlet manifold not sealing properly.
however i had been looking at this pipe (picture not mine) ballancing pipe is it? the one between the two carbs...



however on mine this pipe has been cut into and is connected to the crankcase breather. something like this....



see what i done there??? pretty good artist eh!!!

it has always been like that, was like it when i got the car so never questioned it. but i havent seen it done on any other enginges! is this "mod" likely to be causing issues?

[Jordie]

spray some WD around the inlet manifold, gasket areas etc. if the engine tone changes then its drawing air somewhere.

[minibarnerz]

i KNOW its been drawing air in.... :s was asking if this could be a source, or could cause issues in some other way ie causing the carbs not to ballence etc etc

[Jordie]

well it would only be the source if its drawing air in those pipes.

check if the pipes are not split, secure and not leaking at the end for example.

like i said, WD40 will help you narrow down any potential areas drawing air.

[minibarnerz]

Ok, just say there was no air leak from the pipe.... Would this configuration cause an "air leak" by sucking air from the crank case breather or cause any other issues?

[dklawson]

The Y pipe is for emissions. Connecting the two carbs together without the Y is acceptable and will not cause a vacuum leak. Obviously if the hose is loose or cracked it can be the source of a leak.

I would be more suspicious that your leak is from uneven flange thicknesses on the intake and exhaust manifolds. The flanges need to be the same thickness so you can tighten them evenly to the head and compress the manifold gasket properly.

One method that friends of mine use to find intake leaks is with the engine running, open the valve on an un-lit propane torch and pass it slowly around the manifold and manifold flanges listening for changes in the idle RPM.

[minibarnerz]

The Y pipe is for emissions. Connecting the two carbs together without the Y is acceptable and will not cause a vacuum leak. Obviously if the hose is loose or cracked it can be the source of a leak.

I would be more suspicious that your leak is from uneven flange thicknesses on the intake and exhaust manifolds. The flanges need to be the same thickness so you can tighten them evenly to the head and compress the manifold gasket properly.

One method that friends of mine use to find intake leaks is with the engine running, open the valve on an un-lit propane torch and pass it slowly around the manifold and manifold flanges listening for changes in the idle RPM.

ok, so, presuming the hose is not loose or cracked, having it connected to the breather is quite acceptable? thank you.
yes, i think that the cause of the air leak is from the manifold, one of the studs the thread was beggining to strip, a couple of others the stud moved when i tried to tighten them, so i have the head off now and im replacing all the studs, will also check the thicness' of the inlet/exhaust flanges compared to each other. would people recomend using an exhaust compound paste on the gasket too?

[dklawson]

Generally sealants are not used on manifold gaskets. However, I have heard of people doing so in desperation.

The Y pipe setup is something I have not seen on a Mini. I do seem to remember it being used on some of the A-H Sprites and MG Midgets of the same period. I THOUGHT the outlet from the Y was typically connected to a Smiths PCV valve, however, they might have connected to the intake using an orifice plug inline (just a guess on my part). Were I troubleshooting your car's running problem I would simply connect the two carb ports as your first picture shows or I would cap both of those carb ports. Once you have found and corrected the source of the vacuum leak you can decide how you want to connect the hoses to the carb ports.

[minibarnerz]

thank you. will connect them together as shown in the first picture and put a breather filter on the crank case.

[minibarnerz]

My question was not "do I have an airleak"
I know I have an airleak, I was asking if the pipe is meant to be attatched to the breather... N no amount of wd is gonna answer that and secondly I don't want greasy residue all over my engine and carbs!!

[dklawson]

The reason for propane is that there is enough air circulation that it doesn't collect or present a combustion problem. The traditional old-school way of finding leaks was to use starter fluid (ether). Now THAT can catch fire in a heartbeat and cause you a world of hurt.

WD-40 will burn so feel free to use it if you want. However, if it does catch on fire you will have a short lasting fire dripping down the back of your engine block. To each his own though.

By the way, has WD-40 in the U.K. started becoming available in the "new" spray can with the flip-up straw on the spray nozzle? I hope for your sake that it has not. I HATE the new aerosol cans. I'm ready to buy WD by the gallon just so I can use a simple pump sprayer instead of the new aerosol cans.

[dklawson]

DILLIGAF, we both happen to be right. In aerosol form WD-40 burns. Sprayed on a surface and heated, it does not (about the same as diesel or kerosene). See below:

If WD-40 did NOT burn, it would be pretty useless when trying to find intake manifold leaks. Why not just spray water if WD-40 doesn't burn?

And propane, as I stated before does not pose some higher level of danger. It it is quickly dissipated by the air currents in the engine compartment with the engine running. But by all means, use what you are comfortable with.

Edited by dklawson, 05 March 2012 - 01:01 PM.

[minibarnerz]

I'm not spraying anything anywhere, my head is off for a start so it's not running... And im not spraying anything greasy on my engine, mentioned it's idling erraticly anyway so won't notice achange!

[minibarnerz]

I think it's leaking from my inlet manifold, which, last time I checked was defo part of my engine.... But still, my question was in revance to the Allen ing pipe being connected to my crankcase breather anwwhether this was ok or it if would b causing an air leak by sucking air from the crankcase.... Where I can't get to spray anything! :/

[minibarnerz]

Please read my original post.... It's got nothing to do with asking if my air leak is coming from my manifold! I'm not a complete noob, I built my engine from scratch myself, I'm aware of the effects of spraying wd (an oil/grease whatever u want to call it) i don't want to do that, I spend a lot of time cleaning my engine and keeping nice. Plus I am 95% sure it is leaking from there and am already doing steps to solve that.... Please read the thread!!!

My question was, and still is,

"is having the ballancing pipe on the carb connecting to my crankcase breather going to be causing an issue? As it will be trying to suck air from the breather!

I don't see how spraying any amount of wd onto my manifold is going to answer that!? Also.... My head is off the car...

Thanks for your help anyway, but it seems your getting a little confused about my original question! I admit the topic title may be a little misleading!!