Quadrajet fuel inlet repair
 

Not sure if this should be in the ‘Street’ forum, but since it’s for my Judge, figured I’d post here first.

I had Cliff R. rebuild my 7040573 carb. It looks great and I think it runs ok, but fuel has started to leak out of the inlet pretty badly. I tried replacing the gasket (which looked like it wasn’t the right size) with a correct one. Unfortunately, the only ‘correct’ one I had came from another carb and it may be decades old. Anyway, the leak stopped for a day, but then returned. I did a Google search and found a site called QuadrajetParts.com. I reviewed the site and there were a couple of options available to repair the leak:
1. Extra thick nylon gaskets
2. Extended-thread inlet (0.500”)
3. Extended-thread inlet (0.650”)
4. Self-tapping fuel inlet

I ordered all 4 options, and figured I’d try them out in that order. I’m not crazy about going the self-tapping route. This site also offers a milling service where they drill out the inlet and install a heli-coil. I think I’d rather have them do that then go the self-tapping route (if none of the other fixes work). The one downside is that I have to disassemble the carb and just send them the body. I’m a little nervous about taking apart a carb that Cliff put together, since I’m not confident that I will get it back together as well.

Have others had success with any of the options I listed?


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Had one Heli-coiled some years ago. End of problem, spensive. And they milled maybe 1/8 inch off the face of the inlet but it's a Chebby so that's OK.

Yeah. The price was like $75. If that works, I’m ok. It’s the disassembly/reassembly that scares me. LOL


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On my judge carb the fuel inlet threads were starting to let go. I got the helicoil kit and installed the thread insert and it has been good ever since. Ya it would have been better to have a machine to cut the new threads but I was able to do it free hand. The helicoil is the best repair and the others may just be band aid repairs. I would not try to put a self tapping inlet in. If it fails and you decide to put a helicoil insert in, you may not have enough material in the bore to cut proper thread for the helicoil. That would be a really bad deal then!

Thanks Josh. That’s my exact concern about the self-tapping inlet, that if it doesn’t work, then I’m SOL and potentially ruin my 7040573 carb body. I figured the thicker gasket and the inlets that screw in a bit further were harmless fixes so I figured I’d try those first. I think this Qjet shop also sells the Helicoil repair kits as well. I’ll take a look at those. Does that get done with the carb on the car, or would you remove it and do that on a bench?


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I would suggest that if you can revise or return the self tapping inlet (filter housing), that you might want to do that.
I believe you have there the bare none, rearest/most valuable 1970 Pontiac Quadrajet;
I would never use one of those self tapping filter housings on that carb.
I also agree that the heli-coil kit might be the way to go.

If you decide to buy the kit, and only need it for the single repair, I'll buy the rest of the kit off you when you're done - those kits are pricey... I have a 1968 Pontiac Quadrajet that holds well enough, but it looks terrible, so I probably will need to do a feul inlet thread repair soon enough.

Thanks. I went to the website again and they talk about using that Heli-coil kit only if you have a milling machine or some kind of jig. That makes me nervous too.


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you should be able to use a drill vice and drill press to ensure that you drill out the old threads straight;
Then again, you could probably just use a bench vise and care with a hand drill... which brings me to this reply:

It's only drilling out the old threads that would need the most care;
Re-tapping, for the insert would be done by hand.

Have you ever used heli-coil kits before?
They are pretty straight forward.

If you are nervous about it, I'd recommend finding a suitable step-in replacement, so that you have the option to drive, and sending to someone like Cliff to install the heli-coil;
I believe that if you make arrangements with him before hand, you should get the quickest turn around.

Not necessarily...I lost my first '68 GTO because of a leaky inlet. I thought, 'What's the worst that could happen? It'll go dead and I'll have to walk.'
Instead...Poof!....my car went up in flames.
Moral is, fix it properly the first time and be done. If it starts leaking while you are driving, it takes no time for the fumes to build up and there are some ignition sources under the hood.

Have you talked to Cliff about it? I'm certain he can provide you with a permanent fix.

This is my next step. I have another carb I can use for now, but since I was kicking around the idea of a cam swap, maybe the timing is perfect. LOL.


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I got a chance to pull the carb today and it appears as though this was perhaps repaired in the past? It looks like the first couple of threads are ‘recessed’ further and the inlet bolt does not begin to thread in until the 3rd or so thread. Is this normal or might this be the culprit?

https://uploads.tapatalk-cdn.com/201...86cf9c95d9.jpg

https://uploads.tapatalk-cdn.com/201...30f9cdd3e6.jpg

https://uploads.tapatalk-cdn.com/201...6dce3b3905.jpg



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that is definitely heli-coiled already;
it looks to be in there almost enough to put an insert infront of it - I am not sure why it would be that far in.

Ok, next idea;
Look at your filter housing - some of them don't go very deep, maybe you need to find one t hat has a deeper threaded section?

Ok, so this is going to sound strange. I pulled the carb off and replaced it with another Q-jet I had used in the past. I got it running, set the idle mixture, and noticed that carb was leaking too. I figured, let me change that gasket. Did that, but it still leaked. But when I looked at the leak really close, it seemed like it might be coming from where the fuel line goes into the filter housing. I installed one of the new filter housings I bought (which has a couple of extra threads in it). The fuel line fitting looks like it’s seen better days, but just as a test, I ran some plumbers tape ape around the threads. Fired it up. No leak.

I realize this is not a permanent repair, but could the fuel fitting that goes into the inlet housing wear to the point it leaks. I also don’t like that it’s a direct hard line from the carb to the fuel pump. I realize that’s the design, but I wonder if because there is no flex in it, could vibration wear it down. Just a thought. I also have no idea how old that line is. Could be original for all i know. I do not believe I have ever replaced in the 14+ years I’ve owned the car.

My thought is to get a replacement fuel line and bolt the 7040573 back on, unless from the photos I shared you think I should get that heli-coiled anyway.


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I also emailed Cliff, but that was before I tried the Teflon band-aid. Will let you know what he says.


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Most repro fuel lines from pump to carb are a bit off so they tend to not want to go into the carb dead straight. Either tweaking the line till it goes in straight and true or install the carb end first and then tweak it at the fuel pump end.

Ok, thanks. I ordered the new fuel line and will attach it to the carb first.

Do I still need another heli-coil in my carb even if I use a deeper fuel inlet?


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No.

if you find a deeper fuel filter housing, then you would negate the need to add more insert length.

Ok, thanks. When my new fuel line gets here I’m going to try the deeper-threaded insert I bought from the QuadrajrtParts place.


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