Quadrajet 7029282

[Kavesh]

Hello all

My carb has been working well for while now and then at the worst possible time decides to get sick, at my daughters matric dance (prom).
At the drop of point a gave the motor a couple of revs, nothing hectic and the motor stalled. After a couple of attempts to restart she started but the idle was now very erratic.
Managed to drive her home, while driving she was fine no issues, but when stopped at the lights the idle was not good.
Next day started up and was smoking a lot, black smoke and engine very shaky, tried gentle revs and it did not clear so shut the motor off and stripped the carb.

See pic of what a mess I found.  fuel in the baseplate.
I originally thought it is the well plugs, but I am not so sure now. I have previously epoxied these and the epoxy is rock hard. (I sealed these just as a precaution before).
Could a stuck open needle and seat have caused this issue?

Would appreciate any advice on this please,
Thanks

[Kenth]

This maybe?

[Kavesh]

Thanks for the reply. I did not have the little clip on the needle.

[Cliff Ruggles]

The carburetor will NOT care for function purposes whether you have the clip on the needle or not.  There are hundreds of carburetor designs out there that don't even use them.

What the clip does for the Q-jet is to lift the needle off the seat as the fuel evaporates away and prevents the soft tip from sticking or getting "glued" into the fuel inlet seat. 

I'm not saying here not to use the clip as being able to re-fill the fuel bowl after months of sitting is pretty important and I've seen a few cases where the carb sat so long that the needle actually got glued in hard enough the carb had to come apart to get it freed up.

I would mention however that if you use the little clip on the needle that it need to be "adjusted" properly or it isn't doing you any good right to start with.  The opening is too big and if you just push it straight on the needle it will not lift it when the float drops to the lowest position.  The opening that slips over the needle also needs to be pinched down some with a small pair of needle nose pliers or it will not fit well and can tilt sideways (causing flooding in extreme cases) in use and even slide off. 

I custom adjust every single one on all carbs built here and check to make sure it's actually lifting the needle off the seat like it's supposed to.  I suggest to anyone reading this to do the same.....

[Kavesh]

Cliff, thank you!
I have put together a couple of carbs in my time and every time I used the little clip I would try and see what it does to the needle and every time I would tell myself it does not seem to make the needle move.
I would assume that perhaps its my bad eyes or it needs to be in operation to actually make the clip useful. This is the first time I have heard that the clip needs to be adjusted to function.

I have watched many videos and read many articles on rebuilding these carbs and never have I come across this little secret.

I would imagine it will be a delicate process to not damage or loose the clip, which I have done before

[Cliff Ruggles]

I've tried to watch a few Youtube videos on building Q-jets.  I can't get thru more than a minute or two of them without getting ill!......

[Kavesh]

Lol, Cliff, I know what you mean. For someone like me before finding this forum and chatting to people like John Herald Jnr and a couple of others, it was my only source of information.
You have to watch dozens of video and extract bits and pieces from them.

 

[Kavesh]

Anyways, back to my issue, will a open needle and seat cause the amount of fuel in the baseplate per pic in the post above.
I would want to reuse the main body if I can as its the best float bowl I have.

[quadrajam]

I have seen that same fuel syrup in that same cavity with no running issues.
It is surrounded by gasket and any fuel that weeps by the gasket would be
very slight.
Prolly was debris in the needle/seat. Clean it all up and new kit. Check that
fuel filters are OK.

[Shiny]

Check the seating surface under the fuel inlet seat.  Mine was rough from corrosion and/or prior grit-blasting.  It wasn't obvious, but it leaked a little until machined flat again.

I also had flooding I attributed to rust in my fuel sender.  The particulates were obvious when I opened the carb, but were small.  I think it may not take much debris to cause seating issues.

[Kavesh]

Many thanks for the replies. This gives me a little more confidence with my main body.

Very surprised about about the comment that there can be this liquid around the base. I assumed that area would be mostly dry.

Hopefully I get some time this weekend to sort it out and get it working nicely again.

[Cliff Ruggles]

It would be difficult for fuel to get into that void in the baseplate unless the large rear bottom plugs are seeping out some fuel.  I pressure test them here by putting 140psi of compressed air into the holes in the rear of the fuel bowl that supply fuel to the secondaries.  With a little soap/water mix over the plugs you will very quickly find the smallest leaks.  Although leaks are rare on the 1969 and newer units (despite what the "gurus" making Youtube videos tell us) you will occasionally find one that leaks slightly around the pressed in aluminum plugs.

The quick and easy repair is to gently "peen" the material over and around the plugs with a small machinist hammer.  99 percent of the time that is all that is needed to seal them back up.  Dabbing any type of epoxy over leaking plugs, especially JB Weld is a complete waste of time.  I see more carbs messed up by that stoopid repair that I can count.  Building up a layer of epoxy over the plugs can hold the baseplate away from the main castings when it's tightened up.  This puts the part in a bind, can cause the throttle shafts to stick, and also prevent the gasket from sealing causing a very difficult to find vacuum leak......FWIW.

Once again the "gurus" from ever Forum you go on, or Youtube video you watch on this topic tells us to put JB Weld over bottom plugs that most likely weren't leaking in the first place.  JB Weld is also USELESS for that type of repair right to start with.  It gets "soft" over time, and doesn't stick well enough to seal them up right to start with.......

[Kavesh]

Thanks again Cliff for your advice. I will try and test the bowl this weekend for leaks.

I also thought it not normal to see so much fuel in the baseplate. I wonder if somehow there is a hairline crack in the bowl. Could that even happen?

I will post an update once I have assembled the carb.

[Cliff Ruggles]

I've seen quite a few splits or cracks in the 1965 thru 1968 Q-jets that will cause them to leak.

The Carter castings are also bad for being porous and leaking fuel thru them.  I've found quite a few "leakers" made after 1968 but almost all of them were Carter castings.

I've also found a few Q-jet bowls that were leaking between the passages under the DCR's over into the idle tube area.  This is very difficult to troubleshoot and locate the problem but I've found quite a few of the Edelbrock 1904 thru 1910 units defective in that area and several 7041262 Pontiac castings doing the same thing.   

I've also found a handful of later SMAB truck castings with the same issue.  About the only way you can find that problem is to completely fill the bowl with fuel and eventually some will migrate over to the passages leading down to the mixture screws and start dribbling. 

You can also fill the bowl mostly up with a soap/water mix and very carefully blow compressed air into the DCR's and you'll get some bubble over in the fuel bowl area where the idle tubes are located.  That move is difficult because it's hard to seal off the compressed air during the test.

I have an Edelbrock 1904 in here right now that's got a bad casting.  It was sent in by a customer who said it has never ran well despite numerous rebuilds and attempts to tune it.  I found nothing wrong with it first time thru, then did a pressure test and found the driver side DCR passage leaking over into the main fuel bowl, so it's junk.......

[Kavesh]

So I believe that the carb I was using was a Carter built unit, as it did not have the fill carb number, it was a 29282.

I decided to assemble another one from my shelf, with the correct QJ part number 7029282. I needed to fix the airhorn warpage which I did with some heat and G clamps. I had dismantled the airhorn air doors prior. After fixing the warpage I found that the shaft for the secondary doors was binding. I checked for straightness and it was fine. It seemed the 3 holes through which the shaft goes is now slightly out. After some though I used a perfect size thread bar as a file to realign the holes. I hope this does not create another issue!

Apart from the fuel inlet being damaged this body was decent. I used epoxy to seal the fuel inlet. I installed an inline fuel filter as I can no longer use the internal filter.

I am reusing the baseplate as I had previously repaired the shaft bushes.

While assembling the internals I remembered Cliff saying that the float clip will need some adjustment to work correctly. Armed with my needle nose pliers while holding the clip it vanished from sight never to be found again Anyways proceeded to assemble the carb for now just using the new needle and seat and accelerator pump and old gaskets. Once I confirm everything is good I will use my new gaskets.

I had previously tried to remove the ATP adjustment screw after removing the cap, but it would not budge. I hope there is no vacuum at that point.

I fired her up and see was purring like a kitten . Mix screws are 2 and a half turns out. It was now late and performed some minor mixture adjustments. Curb idle screw is barely touching the stopper. I would have expected the motor not to idle but this was always my experience, choke fully disengaged.

Hope to take her for a drive later in the week.

Please see some pics will be posted below