Cleaning Rochester MV4 Quadrajet carburetor

I dismantled the above carb' as I've done in the past to clean it and sprayed the various jets etc. with carb' cleaner. The force of the spray on this occasion dislodged a small spring(one inch long and eight on an inch wide)and a small brass tube( inch and a half long and three sixteenth of an inch wide). I found them on the bench and did not see where they came from but suspect that it is the spring that goes under the power piston. No. 24 on my Instruction Sheet and that the tube which I cannot see on the Inst. Sheet slides down inside it and sits in the hole at the bottom of the "well" that the spring goes into. If that is the case is the tube just a push fit in the hole or what? I would be grateful for confirmation or otherwise.

The brass tube sounds foreign. Post a picture of the brass tube.

Those emulsification tubes are supposed to be in the top section of the carb body sounds like you lost one.
The spring if it is about 2 inches long maybe a bit less and is about 1/4 inch diameter that is the one under the power piston...yes.

see pic and explanation

kghost said:

Those emulsification tubes are supposed to be in the top section of the carb body sounds like you lost one.
The spring if it is about 2 inches long maybe a bit less and is about 1/4 inch diameter that is the one under the power piston...yes.

see pic and explanation

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Chris and KGHOST thank you very much for your replies. The brass tube is one of the emulsification tubes as suggested. It must have become detached when I separated the carb', if it hadn't fallen off already and lodged itself in the lower half, where I was convinced it had come from. Thanks once again.

I would be looking for a new carb top. They should not come out.

Docksidemarineservices said:

I would be looking for a new carb top. They should not come out.

Click to expand...

I agree with Chris BUT, It is not uncommon for this to happen and it is spoken about this very issue (emulsification tubes coming out) in rebuild/repair literature and it is said to do what I suggest. re insert the tube, tap in lightly and to "pinch" the aluminum very carefully to hold the tube in place.

The Rochester I recently rebuilt for my friends Chevelle, both the tubes came out. Symptom of a well used carb.

I did as I said and it works fine.

If another top is available then by all means replace it but if not then with a little careful re installation you should be fine.

Which emulsion tube in this 4MV exploded view became dislodged?






If the emulsion tube(s) dislodged from it's respective port, by all means replace that section.
Even if knurled or staked, you will not want to risk a second occurance.


.

The emulsion tubes are not shown in parts breakdown as the are not supposed to be removable parts. If the the airhorn ( carb top ) were to be flipped upside down in the above illustration, four of them could be seen, two smaller, and two slightly larger tubes. Some Qjets only have two tubes, but these were automotive type, not marine. As Khost had mentioned, it is fairly common to have these fall out and also as he mentioned, a gentle tap or two is usually enough to hold them firmly in place. I have done this on a countless number of Qjets, and it works.

.................

Fastatv said:

The emulsion tubes are not shown in parts breakdown........
I realize that!

........ as the are not supposed to be removable parts.
Exactly.

.......... As Khost had mentioned, it is fairly common to have these fall out and also as he mentioned, a gentle tap or two is usually enough to hold them firmly in place. I have done this on a countless number of Qjets, and it works.
I don't disbelieve you.
However, why are they prone to coming loose in the first place?

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However, why are they prone to coming loose in the first place?

Because they are brass pressed into aluminum and the constant temp cycling of the aluminum and the brass causes them to loosen over time.
They are pressed in (press fit) when built and that in itself deforms the brass a bit as it is softer than the aluminum............I am sure if they were overly concerned they would have made them threaded. Many outboard carbs have threaded emulsification tunes so they can be removed and cleaned.

Why throw away a perfectly good carb top because a tube loosened and fell out when it is so easy to re-install...........

Again a slight "swage" or "pinch" of the aluminum around the tube and it is in for good.

As a single boat owner they may not have access like some of us to extra parts..........

a drop of locktite works well too....the trick is to reinstall them so they are at the correct 'depth'.

RicardoMarine; sorry about delay in replying. It was the outer emulsion tube left side when facing stern. Thank you for your interest.