intake manifold drain nut?

[mint 61]

After I shut down my SII, there is gas leaking from a nut on the bottom of the intake manifold, it's leaking right onto the exhaust header below which is a bad thing for obvious reasons. I've looked through the wsm to no avail, can anyone shed any light on this bolt, is its purpose to drain excess fuel out of the manifold? I've tightened it a little, but didn't want to screw anything up without knowing what it was. Any insight would be appreciated. Thanks.

 

[RootesRacer]

After I shut down my SII, there is gas leaking from a nut on the bottom of the intake manifold, it's leaking right onto the exhaust header below which is a bad thing for obvious reasons. I've looked through the wsm to no avail, can anyone shed any light on this bolt, is its purpose to drain excess fuel out of the manifold? I've tightened it a little, but didn't want to screw anything up without knowing what it was. Any insight would be appreciated. Thanks.

Its doing exactly what its supposed to do, which is to drain fuel out of the intake.

Now your job (should you wish to accept it) is to figure out why the fuel is in the intake and not the carbs.

Hint, it has something to do with the bowls overflowing.

 

[alpine_64]

I wasn't sure the SII had this manifold, but i know the S3 cars has this, and yes the drain drops a bit of fuel onto the exhaust. It is a minimal amount and the exhaust should not ignite it.. but i understand your concern. there is a name for that specific part.. but it escapes me at the moment, we discussed this issue on the forum several iterations ago.

 

[65beam]

nut

it's called the intake manifold drain pipe. it similar to a brake line, roughly 6 inches long with a brass fitting soldered to the bottom. it is secured to the intake using a brass end similar to the nut on a compression fitting and a ferrule used in the compression fitting. the brass fitting on the bottom has a small metal ball in it which is secured by what looks to be a cotter pin. it allows the fuel to slowly drain past the ball. it was set at an angle to direct the fuel away from the manifold. the tube is barely visible on the engine photo of my red lemans on photobucket.

 

[mint 61]

No pipe on mine, just a nut on the bottom side of the manifold. I guess I'm gonna have to bite the bullet and pull the carbs for a rebuild. The car only has 37k miles, but it has sat for 30 yrs. I've fiddled with them a little, and they're still running rich, which I understand is a common problem with the twin Zeniths. This should be interesting!

 

[RootesRacer]

No pipe on mine, just a nut on the bottom side of the manifold. I guess I'm gonna have to bite the bullet and pull the carbs for a rebuild. The car only has 37k miles, but it has sat for 30 yrs. I've fiddled with them a little, and they're still running rich, which I understand is a common problem with the twin Zeniths. This should be interesting!

You should take a pic and show us, the correct location is dead middle of the intake beneath the main plenum log.

Is the "nut" open?

The original config has a copper tube attached to the manifold fitting and a spring or gravity loaded ball bearing acting as a one way valve, where fuel can get past the BB but air cannot be sucked into the intake.
The tube is flexible enough to be able to route it where the fuel drips do the least dangerous place heat wise.

The needle and seat in the carb is probably worn, 37k or not.
If you are running an electric fuel pump, be sure to regulate it down below 2psig or even a new needle valve may overflow the bowls.

 

[JonPiz]

re manifold drain

I had the problem where I couldnt get the car started because the electric fuel pump just kept pumping fuel into the carb which must have a faulty float valve which flooded the manifold. I had got rid of the drain as I had changed manifolds but there was no where for the fuel to drain. I decided I cannot be bothered with electric pumps anymore and are currently converting back to manual (well its retro isnt it). It worrys me that neat gas could be dripping on or near a hot exhaust manifold, but I suppose you dont hear of many engine bay fires with the Alpine.

 

[mint 61]

Ok, I'll try to take a pic tonight. I wonder if the pipe is broken off and just the nut is left on the manifold. It's kind of a hard spot to get a look at. Thanks

 

[tony perrett]

Don't make the mistake of blocking the drain with a screw. Raw petrol, if dumped in the manifold, will find its way past the pistons into the sump oil.

 

[Hillman]

Hate to resurrect a dead thread but after owning my Alpine II for several years I realized that the 'plug' in the manifold was actually the fitting for the tube, minus tube. I found what apperaed to be a correct tube in my misc. parts, but somehow the ball had escaped.

I never could get it to idle below 1K RPM and it always 'bucked' a bit on acceleration. I blamed my tuning skills. Will get a real plug tommorrow and see what changes. Any predictions?

 

[SoCal'beaming]

Sorry Guys ... pluged that ... had no issues ... though I 'am running hotter plugs ,,, no build up in the intake if it's running warm enough ...

....... David

 

[snamelc]

I have a Series II Alpine also and when the engine began running rough, I discovered the intake manifold drain tube was missing. It had broken off, apparently from vibration. I solved the problem by plugging it off, my thinking being that few if any other LBCs have this fitment so why is it necessary on an Alpine. It has been about 10 years since the plug was installed and the engine continues to run flawlessly. Only if I were running an electric fuel pump would I consider hunting down another drain tube.

Bill

 

[bernd_st]

Can only underline that. Brazed my original brass Tube closed and never had any issue with that. At least in combination with the original fuel pump. Would rather call it one of the best mod's you can do to your early series...

 

[s2willdo]

Can only underline that. Brazed my original brass Tube closed and never had any issue with that. At least in combination with the original fuel pump. Would rather call it one of the best mod's you can do to your early series...

Hate to resurrect a dead thread but after owning my Alpine II for several years I realized that the 'plug' in the manifold was actually the fitting for the tube, minus tube. I found what apperaed to be a correct tube in my misc. parts, but somehow the ball had escaped.

I never could get it to idle below 1K RPM and it always 'bucked' a bit on acceleration. I blamed my tuning skills. Will get a real plug tommorrow and see what changes. Any predictions?

Is this the drain pipe? If so it must require another fitting to connect to the intake. Does anyone have a complete picture. Raw gas pools in my intake.

 

[Jimjordan2]

Not sure about the early series, but in a series V, if that had a loop in it, it would be for the rocker arm oiler. That probably is what that part is. Just my thoughts.

 

[Gary T]

65 Beam has described the same drain pipe that I had on my Series II and it did have a ball held in by a very small cotter pin. The Parts Manual shows Series I and II manifolds had the drain tube, olive connection and nut as well as the check ball arrangement. For Series III the drain was just a long tube with no check ball. My friend is working on an Austin Healey 3000 and it has the drain tube with no check ball and with the electric fuel pump, we did see raw fuel leak out of the manifold, which we now needs to corrected.

 

[jumpinjan]

Is this the drain pipe?

I don't know what it is. The proper drain pipe has a brass tube (with the check ball & cotter pin secured) silver soldered to the tube end. When it works, it works great.
Jan

 

[s2willdo]

Thanks everyone. I’m going to start looking for one or make one. I recently put in an electric pump so that must have had something to do with pooling of raw gas in the intake.

 

[beamdream]

Is this the drain pipe? If so it must require another fitting to connect to the intake. Does anyone have a complete picture. Raw gas pools in my intake.

Nope, definitely not the drain pipe. Looks like the rocker oil feed pipe as suggested, someone has adapted it for the manifold drain, totally useless without the check ball.

My experience with the twin Zeniths is that it's fairly common for fuel to drip out on shutdown, and particularly so if you over pump the pedal on start up and it doesn't catch straight away.

I've managed to judiciously bend the drain pipe so any fuel clears the exhaust manifold; but in the worst case scenario I've only ever had a slow drips from the drain with the engine not running.

 

[bernd_st]

This is how an original drain pipe should look like. A 1/4" chromed steel ball intended to act as a shut valve once manifold vacuum rises: