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Quadrajet Rebuild

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Old Aug 15, 2016 | 10:37 PM
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Default Quadrajet Rebuild

Hi Guys, On my way though my first car rebuild. It's an edelbrock 1902 that was used by my father on his 68 corvette back during the 90's for a few months. He eventually put the stock carb back on. I have these greyish deposits inside the carb and I can't figure out what the hell it is or how to get rid of it. Carb Cleaner and chem dip WHOLESOMELY INEFFECTIVE. Looks like this Picture


http://image.superchevy.com/f/366820..._tuning%2b.jpg

I took some sandpaper of 500 grit to the accelerator pump bore and the primary rod hanger bore to clean it out and it came off as a dark dusty grey. A majority of it is in the fuel inlet which leads me to believe it was a fuel additive. Also it's not present in any quantity on the airhorn or where fuel didnt touch it. Was thinking it was lead additive because we run it for the exhaust valves.



Not sure though. Anyone?
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Old Aug 16, 2016 | 08:07 AM
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Originally Posted by NothingSpecial
Hi Guys, On my way though my first car rebuild. It's an edelbrock 1902 that was used by my father on his 68 corvette back during the 90's for a few months. He eventually put the stock carb back on. I have these greyish deposits inside the carb and I can't figure out what the hell it is or how to get rid of it. Carb Cleaner and chem dip WHOLESOMELY INEFFECTIVE. Looks like this Picture


http://image.superchevy.com/f/366820..._tuning%2b.jpg

I took some sandpaper of 500 grit to the accelerator pump bore and the primary rod hanger bore to clean it out and it came off as a dark dusty grey. A majority of it is in the fuel inlet which leads me to believe it was a fuel additive. Also it's not present in any quantity on the airhorn or where fuel didnt touch it. Was thinking it was lead additive because we run it for the exhaust valves.



Not sure though. Anyone?
the zinc material the carb was cast from was attacked by water in the fuel. later Q jets moved the sealing gasket to a area inside the threads so this would not happen. you will have flooding problems as the material will keep flaking off and getting into the needle/seat. I fixed this problem by soldering a fine screen on the input side of the needle seat. also you need to have the threaded area replaced with a helicoil as those threads will give way and you will have a fuel leak and maybe a fire. the screen on the inlet side of the needle seat to catch the pieces to prevent flooding
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Last edited by PAmotorman; Aug 16, 2016 at 09:25 AM.
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Old Aug 16, 2016 | 08:53 AM
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the later and earlier fittings. notice where the sealing gasket is located
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Last edited by PAmotorman; Aug 16, 2016 at 08:58 AM.
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Old Aug 16, 2016 | 10:30 AM
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Originally Posted by PAmotorman
the later and earlier fittings. notice where the sealing gasket is located
That....Is alot worse than I thought it would be. ****. Thanks! Will solder the screen on later too. I got some perfect size super fine screens laying around for that. Worried about the threads now that you mentioned it. They visually look fine except for the last few threads. What a shame since this quadrajet only had about 5k miles on it. Are there any options for repairing the inlet?

I'll try and run it to see if it ends up leaking out. Maybe I'll even JB weld or qwik steel the inlet to the body and run an inline filter because I'm a bubba
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Old Aug 16, 2016 | 10:44 AM
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After I started using a torque wrench to seat a new nylon gasket at 33.5 foot pounds I never had any sealing problems.
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Old Aug 16, 2016 | 10:56 AM
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Originally Posted by NothingSpecial
I'll try and run it to see if it ends up leaking out. Maybe I'll even JB weld or qwik steel the inlet to the body and run an inline filter because I'm a bubba
Speaking of an inline fuel filter, I'm in the process of fabricating an inline fuel filter using a new steel fuel line, a Summit 6an fuel filter and associated nuts/sleeves. Lars has a good write up for fabricating inline fuel filters.

http://www.lbfun.com/warehouse/tech_...uel%20Line.pdf

My plan:
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Old Aug 16, 2016 | 10:56 AM
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Originally Posted by NothingSpecial
That....Is alot worse than I thought it would be. ****. Thanks! Will solder the screen on later too. I got some perfect size super fine screens laying around for that. Worried about the threads now that you mentioned it. They visually look fine except for the last few threads. What a shame since this quadrajet only had about 5k miles on it. Are there any options for repairing the inlet?

I'll try and run it to see if it ends up leaking out. Maybe I'll even JB weld or qwik steel the inlet to the body and run an inline filter because I'm a bubba
unless you are into NCRS points chasing I would just find a better carb because if the filter fitting blows out you could have a fire on your hands. some Q jets can have a heli coil installed to fix the threads but you still have the flaking problem. check the needle seat threads in the body as they also get eaten away. i have rebuilt many Q jets and some are not worth messing with

Last edited by PAmotorman; Aug 16, 2016 at 10:58 AM.
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Old Aug 17, 2016 | 02:46 PM
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Originally Posted by PAmotorman
unless you are into NCRS points chasing I would just find a better carb because if the filter fitting blows out you could have a fire on your hands. some Q jets can have a heli coil installed to fix the threads but you still have the flaking problem. check the needle seat threads in the body as they also get eaten away. i have rebuilt many Q jets and some are not worth messing with
I brought the carb over to my buddys house. We took a look. ITS FUCKED. The threads are drilled and helicoiled for hte fuel inlet, the seats threads are shot, there's epoxy DEEP in the fuel inlet. He told me it looked like someone left it in chemdip too long and wrecked the thing. Probably my Dad lol. It's now my practice carb for drilling the air inlets and modifying.

@ green 71. Appreciate the tip. That'll be helpful when i get to that point

Last edited by NothingSpecial; Aug 17, 2016 at 02:47 PM.
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