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Spitfire engine breather


NEIL1809

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My Spitfire 1500 was recently tuned. The tuning centre told me that with the engine breather pipe connected to the carbs,  the engine would not idle properly because the fumes were causing an incorrect mixture. They have linked a pipe between the two carbs breather connection and have run a separate pipe from the breather rocker cover exit under the car so that the fumes exit into the atmosphere and not into the carbs. The car runs fine like this but I can smell the fumes. Any comments please.

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Probably a bit of wear on the engine (rings) allowing a bit of crankcase pressure. they have done the obvious thing to get it to run better.

A good idea to run the pipe into a bottle/catch tank so oil doesn't get dropped on the road (can cause nasty accidents, especially for bikers, and sometimes cars)

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I would look at the pipe whilst running the engine and give it a rev. Can't imagine the fumes would affect the running that much - unless your rngine is fubar.
I ran some carbs without the engine breather and ran a pipe under the car just like the set up you have now, couldn't stand the smell of the fumes so swapped the carbs. I also noticed the engine leaked oil from the rocker cover bolts without the fumes being sucked into intake manifold. Car still runs the same but now smells sweeter.

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Thanks for the tips, the pipe I have from the rocker cover to underneath the car really smells of burnt oil after a run, horrible,  I will try the catch tank idea, where can I buy one?

The carb intakes now have a pipe between the two, is that a problem?

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If the pipe runs between the carbs with no opening to atmosphere, there shouldn't be a problem. Would be best to blank off individually though.
I tried a catch tank with a tiny K&N type filter on it, bought it off ebay, still could smell the fumes though. Catch tank was ally and looked very nice but it went back on ebay.

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all i was thinking was that it is getting effectively unmetered air from the other carb, so i spose you would just have to richen the mixture a bit to compensate.
still reckon it is best to seal them off

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Andy,
Is it getting unmetered air or is it losing it? ;D Richen or lean off?
It seems to me that when I had to seal these I removed the brass tubes and after using rubber plugs that eventually fell out I tapped the holes and screwed in socket headed set screws with thread sealer.
All the best,
Paul

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3267 wrote:
Thanks for the tips, the pipe I have from the rocker cover to underneath the car really smells of burnt oil after a run, horrible,  I will try the catch tank idea, where can I buy one?

The carb intakes now have a pipe between the two, is that a problem?


Look at the photo....pushbike water bottle and holder ....or mines a flash ally hikers bottle @ £0.99 from the pound shop

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The pipe between the two carbs doesn't seem to affect the running, the engine runs really well since I had it tuned. I am taking the car back next week to see if they can suggest anything about the smell, will let you know.

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  • 1 month later...

The whole point of the factory setting is twofold, firstly to comply with legal emissions requirements regarding crankcase fumes, and secondly to get rid of the smell. The factory setup works fine if all the bits are there as they should be. There is a small cylindrical plastic fitting which locates in the carb, and onto which the rubber hose is connected. This plastic bit has a restriction in it so that only a relatively small amount of air is drawn into the carb. If the hole is too large, it will upset idle mixture. Have you checked your dipstick to see if the felt seal which fits against the top of the dipstick tube is missing? This will allow too much air to be drawn through the engine and pipework, also making the mixture lean.

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