Scavenge Tube Fitting

[Tim]

I am rebuilding a late model A4 purchased on ebay. It came with a newer carburetor, it has the fifth bolt at the front. The opening for the scavenge tube was plugged. Not with a pipe plug, it looked like it was plugged at the factory. I removed the small metal plug hoping that it would be threaded for an 1/8 npt fitting. No such luck, and the opening is too small to simply run a 1/8 npt tap in it. Has anyone ever come across this? Should I carefully drill and tap for an 1/8 fitting or are there smaller fittings that would work better?

[Al Schober]

If you're not going to rig a scavenge tube (I don't think you need one), I'd just fill the hole with JB Weld.

[JOHN COOKSON]

I think the scavenge tube is required by law.
Neil: Are you logged on?

TRUE GRIT

[Tim]

I am going to install the scavenger tube. Here are some photos.

[roadnsky]

I think the scavenge tube is required by law.
Neil: Are you logged on?

TRUE GRIT

Yep. It's a Coast Guard requirement on updraft carbs to remove pooled fuel and burn it via the intake manifold.

[ndutton]

I think the scavenge tube is required by law.
Neil: Are you logged on?

Looonnngg work day today but look, youze guys had it covered anyway.

[Tim]

A scavenge tube will be installed. The question is what is the best way to install the fitting to the carb.

[ndutton]

A scavenge tube will be installed. The question is what is the best way to install the fitting to the carb.

Drill and tap for 1/8" NPT, install Moyer scavenge tube kit.

Badda-Bing, DONE!

http://www.moyermarine.com/cgi-bin/shopper.cgi?preadd=action&key=FCAR_13_60.0

[Tim]

That's what I thought. I was just hoping the opening was the right size for a 1/8 npt tap and no drilling would be required.

[Dave Neptune]

Plug?

Tim, could your "plug" possibly be a broken off fitting? It looks a bit odd for a plug and the hole does go to the throat. If it is an aluminum fitting broken off re-tapping and the drilling will need to be done very carefully. It does not look like any factory type plug I've seen before.

Perhaps a close up of the plug may help.

Dave Neptune

[Dave Neptune]

Plug PtII

Tim, the drill size for a 1/8 NPT is "letter 'R' .339" as I recall. You may try centering and going through with a bit smaller drill first and perhaps a thread may show. Be very carefull opening up the hole.

Dave Neptune

[Tim]

There is no broken off fitting. The pictures show what was left after I removed the "plug" which was similar to a core plug. It was soft and pried out easily with a small screwdriver.

[roadnsky]

I think David might actually be on the right tack.
Sure looks like a broken fitting in there.

Are you sure the PO didn't just do a mod to do a cover up?

[sastanley]

The scavenge tube fitting is female NPT, so you'll need to drill & tap for 1/8" female on the carb, and screw in a 1/8" male NPT on one end, and have a compression style male 1/8" NPT on the other end to properly mate with the scavenge tube.

I think this might warrant a call to Ken or Don for confirmation..When it comes to carbs, if Dave Neptune hasn't seen it, it is an anomoly for sure.

[Tim]

I have no history of the engine since I bought it used on ebay from a marina in NC. The seller had several different stories of where the engine came from. The date on the castings are all from 1975. There was an 1/8 npt plug in the manifold where the scavenge tube normally connects. The carb was replaced at some point as it is much newer than the engine. The plug in the scavenge tube connection on the carb looked like a core plug, it was soft and removed fairly easily with a screwdriver. As seen in the photos, there is no evidence of a previously installed fitting. I'm just going to have to drill and tap for an 1/8 npt fitting to connect the scavenge tube.