Well I bought a core off ebay and now have a problem, actually 2 problems. First, the fitting that holds the fuel filter had oxidized the threads in the main body to the point that I can't tighten the fitting enough to prevent gas leaking. I suppose this is a common problem. Is there a fix other than JB Weld?

Second, I have removed the top of the carb multiple times because the accerator pump is not pumping. First the level was in the wrong hole, fix it but no change. It work great when the top is off. Any ideas?

 

the proper way to fix the inlet threads is by helicoiling them.
i'll bet your pump cup is as hard as a rock, that's why it doesn't work. have someone with experience helicoil the inlet, then put a kit in it, with a new float. it's hard to tell, from wisconsin, if you need bushings, or if there is anything else wrong with your core.


bill

 

It sounds like you've already put a rebuild kit in it (I would hope, considering you bought a core). Did you polish the bore of the accelerator pump barrel when you rebuilt it. If not I'd start there. Ruggles recommends 600 grit paper. I think I wrapped a drill bit with paper and spun it until all the crap was out of there and it was smooth.

 

Yes I have completely rebuilt the carb.

I doubt that the fuel filter fitting threads can be helicoiled. The threads are very fine, and the housing in thin, anyone done this? You understand that this is ~1 inch hole. I have a later model qjet with a little larger fitting, thought about machining it down to fit leaving it slightly larger than the original. I have a friend that is a machinist for NASA, so that is very doable, if it might work. I have 3 of these carbs and 2 have the same problem and haven't looked at the third. This has to be a common problem.

I have taken the top off the carb twice and with just the plunger in the bore it shoots gas out, so its not the bore needing polishing.

The linkage was in the wrong hole on the lever (see-saw) that activates the pump, but no help.

 

leaving a 600 grit finished hole will chew the viton rubber pump cups that are supplied with the kits of recent years. after 600, use 2000, then finish it with a fine cut metal polish on a dremel with a felt polishing cone. clean the bore well.


bill

 

There is a special helicoil kit for these, and most of the carb rebuild shops can do it. Not cheap - usually $75-$100 for the service.
However, just to check, are you using the right gasket? Most olds use the clear/white plastic gasket that sits on the very bottom of the threads and seal inside the body - NOT the one that slips over the threads and seals on the front face of the body.

As for the pump, the only difference with the cover on vs off is the cover holds the pump stem in proper alignment. My guess would be the bore is the problem and needs to be buffed. Otherwise, just verify that the checkball was installed correctly and its seat was re-formed when you rebuilt it.

 

"I have taken the top off the carb twice and with just the plunger in the bore it shoots gas out, so its not the bore needing polishing."

So, it works without the air horn on, but when you put the lid on suddenly no joy?

That just does not make sense. Maybe if the pump is very incorrect. Can you measure and photograph your Acc Pump, so we can compare to what works?

The check valve ball must be in place and during the rebuild, you re-form the seat for it by tapping a ball into the seat with a hammer and punch, as alluded to above.

If it works w/o the lid in place then it will work with the lid in place. Spring properly in place above the cup seal, right?

 

I believe the difference is in the height of the acc pump with the air horn off. When it is installed the linkage prevents the acc pump from raising as height as it can with it off. Maybe the bottom half of the bore is the problem. I'll try refinishing it described above and seat the check valve.

I'll let you know.

I have it on good advice that there is a helicoil for these Q-jets. Anyone know where I can get one? Not really interested in spending $500 for a rebuild from a professional carb restoring.

Thanks

 

Can't get the helicoil any other way? Not interested in spending $500 for a restoration.

 

Yah, Bill Demmer has already mentioned the helicoil fix. This is not a DIY fix, send your carb to Dean Oliver or Cliff Ruggles, or look for a better core.

 

I moved the posts from your other thread to here and deleted the old thread.

 

sounds like you have the wrong accelerator pump shaft length, you may need to trim the top for a proper shot. your accelerator pump link should be in the inner hole on the pump lever, the outer hole gives a smaller shot and is generally used on chebby's.


bill

 

Well, I figured out what was going on with my 1970 Q-jet. First I switched the inlet fitting with another I had and problem solved, fingers crossed.

Second the accelerator pump, it appeared longer, but wasn't. The spring had several more coils and would bind on compression. I switch the springs and problem solved. The re-build kit was purchased from a professional parts house, but don't remember the brand.

 

Thanks for the update. Good to know.