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Carb Drain Pipe clarification

Scot

Jedi Hopeful
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Hi,

Do not plug these holes. The 2 copper pipes dump excess fuel from the front and rear part of the manifold. Just rebuilt these on my BJ8. They should attach to the oil pan top via a clip and ferrule and 1/2" bolt.
Should be a photo of it in your parts list.
 

Johnny

Darth Vader
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I had mine plugged, but was told not to do that, because when choking the carbs you have to be able to have a drain for the excess fuel. I was told it was difficult to rebuild them with the carbs mounted.
I didn't find it too difficult. I jacked the car up on jackstands crawled underneath, and with the new 1/8" copper tubes attached to the fittings, and held straight,(they can be formed later) I was able to start the threads at the manifold. Once they were started you can crawl out from underneath and tighten them at the manifold.

smile.gif
 

Dave Russell

Yoda - R.I.P
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<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Johnny:
I had mine plugged, but was told not to do that, because when choking the carbs you have to be able to have a drain for the excess fuel.
<hr></blockquote>
I think that manifold drains were a hold over from old tractor designs. The Healey drains are so small that it would take quite a few minutes to drain any serious amount of fuel. I see no particular reason why excess fuel wouldn't just continue flowing down the intake port & into the engine instead of stopping to go down the drain anyway. Zillions of cars have been made without manifold drains & don't seem to have problems. Even the Tri Carb Healeys don't have drains.

If enough fuel drained into a cylinder, more than the combustion chamber volume, there would be a possibility of hydraulic lock & bending a connecting rod. I think that the number of times that this has happened are few indeed.

There are some aviation engine applications that had manifold drains but they were tubes which were large enough to do the job & had ball check valves for one way flow. One of the perpetual problems with them was that the check valves didn't always seal, caused vacuum leaks & poor low rpm running.

Personal preference I think, but can hardly be justified on technical merit.
D
 
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