First time poster, and at my wits end.

I've had my 1974 corvette with the original quadrajet carb (divorced choke) (auto) for a couple years now and have enjoyed it. The car had the original engine up until I decided to drop a crate engine inside for more power. I've been running and driving it, behaving through its break in period as I should be.

Two weeks ago I decided to go to a local car show when I noticed a small leak dripping from the fuel inlet. Naturally it was the tiny gasket on the end of the fuel inlet. I spent a full day running all over DFW finding the correct gasket only to have the fuel inlet stripped and continue to leak. From there, I decided to take the carb to the only carb specialist in town. They rebuilt it, shined it up really nice and installed a Heli coil to fix the leak. Upon getting home and putting it on the car, it began to puke fuel out the top of the vent to the point it fuel washed my cylinders. YAY! So after draining the oil, pulling the plugs, fogging the cylinders, rotating the engine by hand, bumping it over to make sure everything was turning nicely, I decided to take it back to the only carb specialist in town. They pulled the carb apart in front of me suggesting that I have bad gas which was not allowing the needle to seat . They cleaned the carb and reassembled it again. When I got it home I decided to look inside the fuel tank which looks quite clean. I also shot fuel directly into a glass jar from the fuel inlet so as to inspect the quality of the fuel from the tank. It looks clean to me but there could still be particles I just cannot see. I tried reinstalling for a second time, and after bumping it over, it started puking fuel over the top again.

Has anyone come across this issue before? How did you end up solving it? I can not keep continuing to fuel wash my cylinders on this brand new engine during break in. is it time to replace the gas tank now? From what I've read on here, an in line fuel filter is met with half for and half against installing one.

Mind you, the car was running and driving 2 weeks ago with a more filthy carb

 

electric fuel pump?

 

Send it to Lars

 

Just a few of the issues that will cause your problem are:

• Excessive fuel pressure (over 7 psi)
• Incorrect float installed (did they put a brass float in it?)
• Incorrect float level
• Float arms binding on power piston tower
• Float binding in bowl
• Incorrect needle/seat assembly installed
• Seat gasket not sealing against bowl casting
• Float pivot pin collapsed and not pre-loaded
• Float needle clip installed backwards or sideways
• Contamination in needle/seat (did they re-install the in-carb filter, and is it correctly installed?)

Whatever the issue, it sounds like your "carb specialist" is not test running his carb work, which makes him a carb "hack" and not a carb "specialist." Find a real carb builder and your problem should be easy to identify and correct.

Lars

 

This is exactly right......I test every carb I do in my shop......on my wife's 82' Z/28 305....best test engine ever....or my own 406 Vette if it is a square bore. I just bolt them on and fire them up...sometimes I will drive it if necessary.......but usually just fire to check idle mixture and float. If I think you are picky, I will take video of your carb running on my car. Your "GUY" did not do that.....
First red flag is "checking" your fuel......your fuel could have sand in it and it would never reach the bowl if the correct filter is installed. Second, this didn't happen until they touched it. Third, if he isn't testing carbs on a real engine......then he has no business doing carbs......I don't care how good you think you are.....you are as good as you are the day you are assembling it...and you run your build on an engine so it DOESN'T come back. If they built it a second time and it flows over......just punt and never go back. Buy Cliff Ruggle's Q-Jet book and take the top off the carb using his book.......look in there and notice the direction of the needle clip....take a photo......check float level too using Cliff's book.....
A float is a simple thing.....like a small toilet valve....if the float floats, and the needle is clean and seated.....it is not going to overflow.
You can also send it to Lars......he would probably do a thread on this one to point out what was done wrong.

Jebby

 

The Quadra-Jet is not the issue...your carb "rebuilder" is the issue. Did the shop actually rebuild YOUR carb; or did they swap it out with a 'jobber' rebuilt carb? Hopefully, you still have your original carb with all original parts...except for gaskets and seals. Internal assembly and/or setup is most likely the problem.

 

Take heed of the advice of the other posters here. Lars is THE person to get you running again. The only caution I would offer is that if the carb has been Bubba’d bad enough, Lars will likely take a pass. Reach out to him and see if he’s game.

 

Welcome to the forum!

 

Thanks a million for the quick responses!

I should have mentioned that I'm using a mechanical fuel pump in my first post Quick update, I decided to try the shop who installed my crate engine for me, DMS Corvette here in Dallas Texas. I should have known to take it to them first before the "carb specialist" that I used. They explained that the float needle clip looked as though it was "in a bind" (not installed correctly). It is mind blowing to me considering they took it apart and rebuilt it twice. Got the carb home and fired up with no leaks out the top which is a huge relief. Unfortunately I'm all the way back to square one and my fuel inlet is leaking again even with the "Heli coil installed" This was not the case last night.

 

That single statement alone tells me you need to find a different mechanic.

 

Agree. That’s a HUGE red flag.



Well, at least the forum members have provided a pathway to the person who can make the op love his car again.



GOOD JOB!

 

Based on the non-qualifications of the "carb specialist" (he didn't know how to correctly install the float needle clip, causing the float/needle to bind as I predicted in my problems list above), chances are good that the threaded inlet repair was not correctly done, either. If the carb was not machined in a fixture on a mill during this operation (but done by hand as many try to do), the threaded insert is now not installed perfectly perpendicular to the gasket sealing surface. This will cause a persistent leak, which is now not repairable - if they did not do the machining correctly they have destroyed your float bowl. That would be a shame... Before giving up, remove your fuel line from the inlet fitting and remove the inlet fitting. Inspect the white plastic gasket on the end of the inlet fitting and make sure it's not damaged. Replace it if it's not in perfect condition. While you're in there, make sure the fuel filter is installed correctly with the spring behind it. Put some wheel bearing grease on your fingertip and lube the threads on the large inlet fitting. Also lube the white seal. Then install it and snug it down - you should be able to give it a good snug-down with the new stainless threads installed. Before installing your fuel line, lubricate the threads on your fuel line fitting, and put some lube on the back side of the flared feature on the tube where the tube nut rides against the tube. Once everything is nice and lubricated, install the line into the carb inlet fitting and snug it down using a flarenut wrench with a 1" open end backing it up on the inlet fitting. If it still leaks after doing this, they screwed up the machining during the attempted thread repair.

Lars