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Old 03-12-2013, 09:22 PM
Rbyham Rbyham is offline
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Scavenger Tube Needed?

I rebuilt the carb on a new to me 1966 A4 today. Pic shows finished product. Was pretty straight forward rebuild. Just real cruddy inside. My question is that there was no scavenger tube on the carb. You can see the plug on the top flange and the hole at the bottom throat is simply open. My research seems to say the scav is optional and it appears the PO felt no need of one. I would add that when I cleaned her up I noticed a heavy brown color at bottom of air intake throat. Looks like might have been some pooling fuel.

What do you think and is the scavener tube a part I go to Moyer for? Thanks.
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Old 03-12-2013, 09:25 PM
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Two for two

Same answer here as the other post...
Yes and yes.

http://www.moyermarine.com/cgi-bin/s...rebuilder.html
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Old 03-12-2013, 09:28 PM
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I should have pointed out that you want the tube because you don't want fuel pooling in the throat and leaking out that hole.
The scavenge tube reclaims and returns it to be burned.
There is also a good discussion about the scavenge tube here...

http://www.moyermarine.com/forums/sh...=scavenge+tube
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Last edited by roadnsky; 03-12-2013 at 09:31 PM.
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Old 03-12-2013, 09:39 PM
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Quote:
Originally Posted by Rbyham View Post
.... You can see the plug on the top flange ...
It looks like you have a spacer on top of your carburetor which might have been for a PCV valve. Not sure. I have a different set-up. The scavenger tube goes to the intake manifold, yes?
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Old 03-12-2013, 09:46 PM
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Quote:
Originally Posted by High Hopes View Post
...The scavenger tube goes to the intake manifold, yes?
Normally it does unless you have the PCV setup which his pic suggests he does.
(I'm gonna go waaaay out on a limb here and bet Neil doesn't have a drawing for that)

In his case, however, he doesn't even have the tube.
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Old 03-12-2013, 09:52 PM
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Quote:
Originally Posted by roadnsky View Post
I'm gonna go waaaay out on a limb here and bet Neil doesn't have a drawing for that [PCV setup]
Oh, I've got one but it's pinned on the dart board and full of holes.

Please note that the scavenge tube is a USCG requirement and a VERY important safety item, one of the most important.
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Last edited by ndutton; 03-12-2013 at 10:02 PM.
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Old 03-12-2013, 09:54 PM
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Yes I do have indigo Pcv upgrade. How does that impact the scavenger? The top plate is for the Pcv which connects on the back. The plug for the scavenge tube is on the front. Can both tunes connect to same plate? I am really curious why PO plugged the scav.
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Old 03-12-2013, 09:57 PM
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Quote:
Originally Posted by Rbyham View Post
Can both tubes connect to same plate?
Yes.

Quote:
I am really curious why PO plugged the scav.
Because he's an . . . . uh, because he wasn't a member here. Had he been he'd have known better. What did your surveyor have to say about it?
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Last edited by ndutton; 03-13-2013 at 12:34 AM.
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Old 03-12-2013, 09:58 PM
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You might want to check for a possible air leak in the carb joint.

Put the smallest feeler gauge in between the carb halves, especially where there is that extra hole in the gasket. The newer carbs have a bolt there. We call them either 4 or 5 bolt carbs.
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Old 03-12-2013, 10:07 PM
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Quote:
Originally Posted by Rbyham View Post
Yes I do have indigo Pcv upgrade. How does that impact the scavenger? The top plate is for the Pcv which connects on the back. The plug for the scavenge tube is on the front. Can both tunes connect to same plate? I am really curious why PO plugged the scav.
Ok Neil's gonna kill me but, here are a couple of pics of where the scavenge tube connects,,,
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Old 03-12-2013, 10:15 PM
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I think I'm gonna report that post as obscene.
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Old 03-12-2013, 10:19 PM
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Quote:
Originally Posted by romantic comedy View Post
You might want to check for a possible air leak in the carb joint.

Put the smallest feeler gauge, in between the carb halves, especially where there is that extra hole in the gasket. The newer carbs have a bolt there. We call them either 4 or 5 bolt carbs.
I was aware that there are 2 versions in terms of screws. The only gasket i had was a 5 screw. I figured it would work. Are you saying the 4 screws always or tend to leak?
?
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Old 03-12-2013, 10:22 PM
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http://www.moyermarine.com/forums/showthread.php?t=7091 Post #5. Is the port in the manifold open? Is that not a normal spot for scavenge tube? Dan S/V Marian Claire
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Old 03-12-2013, 10:27 PM
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A lot of carbs have laeked. Mine is very bad, and i use goop to seal it. Some guys machine the surfaces. (file or sand paper)

I only know of the one gasket also. I just cut off the extra, makes no difference.
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Old 03-12-2013, 10:37 PM
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Quote:
Originally Posted by romantic comedy View Post
A lot of carbs have laeked. Mine is very bad, and i use goop twould require lots of choke to run. it. Some.. guys machine the surfacebest? I :-) file or sand paper)

I only know of the one gasket also. I just cut off the extra, makes no difference.
I may be able to do a test fire tomorrow and see if there is a leak. I am assuming any leak woulld require lots of choke to keep running... What kind of goop works best? :-)
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Old 03-13-2013, 08:21 AM
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Quote:
Originally Posted by Rbyham View Post
I was aware that there are 2 versions in terms of screws. The only gasket i had was a 5 screw. I figured it would work. Are you saying the 4 screws always or tend to leak?
?
"...All Zenith carburetors produced since the mid 1980's have a fifth retaining bolt in the front of the upper and lower housings. Prior to this generation of carburetors, there were only four bolts holding the two housings together, and all four bolts were located around the float chamber. This configuration left no fastener to pull the front of the housings together. How this fifth bolt (or the lack of it) relates to a rich running condition can best be understood by a quick review of how the internal pressure within the carburetor is regulated to maintain inlet pressure instead of ambient atmospheric pressure..."

To read more...

http://www.moyermarine.com/pressure_regulation.htm
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Old 03-13-2013, 08:41 AM
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Quote:
Originally Posted by ndutton View Post
I think I'm gonna report that post as obscene.
Ok, one more.
This one's RATED "R" Neil so look away quick...


You can see in this one how the scavenge tube would collect any fuel pooling in the carb throat.
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Old 03-13-2013, 10:36 AM
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Jerry... it looks like there are two somethings connecting to the top flange in your R rated picture. I see the rear one is the scavenge tube. What is on the front? Is it possibly the pcv connection? If not let me ask this. Can I connect the scavenge tube and my pcv valve together into front and rear of the carb flange? Thanks.
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Old 03-13-2013, 11:14 AM
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Red face Oh Boy...

Quote:
Originally Posted by Rbyham View Post
Jerry... it looks like there are two somethings connecting to the top flange in your R rated picture. I see the rear one is the scavenge tube. What is on the front? Is it possibly the pcv connection? If not let me ask this. Can I connect the scavenge tube and my pcv valve together into front and rear of the carb flange? Thanks.
It is indeed the PCV outlet. And YES that's where you should attach it.
This pic shows it a little better.
(Man, Neil is never gonna speak to me again )

In my defense, I should point out that this is a very old picture...
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Old 03-13-2013, 11:28 AM
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Yes..the right hand connection goes to Jerry's PCV valve coming out of the valve cover.

edit - shoulda refreshed

Jerry - the paint is even mis-matched!
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Old 03-13-2013, 11:40 AM
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Quote:
Originally Posted by sastanley View Post

Jerry - the paint is even mis-matched!
Well, if I posted a current pic we're gonna really get into off topic territory!
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Old 03-13-2013, 09:02 PM
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Quote:
Originally Posted by Rbyham View Post
Yes I do have indigo Pcv upgrade.
Toe-may-toe, toe-mah-toe
Upgrade, band-aid

(couldn't resist, I confess I had a ghost writer on that one)
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Old 03-13-2013, 09:14 PM
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Jerry.. The pics are very helpful. But I note the nut on your flange bolt appears crooked to me. Could not be cross-threaded? Probably not but it looks off...
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Old 03-13-2013, 09:19 PM
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Quote:
Originally Posted by Rbyham View Post
Jerry.. The pics are very helpful. But I note the nut on your flange bolt appears crooked to me. Could not be cross-threaded? Probably not but it looks off...
Nope. All good there, but thanks for asking...
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Old 03-14-2013, 02:26 PM
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Hey folks. I just got rebuilt carb all buttoned down and ready for test start. Awaiting new fuel tank I had it running direct from portable can to fuel pump. Upon priming with fuel pump handle i smelled gas. Checking I found about 5 drips per minute coming out of scavenge hole in air throat. I obviously will not try start up. But is this at all normal? I have scavenge pipe on the way from MMI but still this feels like too big a leak. Could I have messed up on carb rebuild?
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