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Post Info TOPIC: Carburetor rebuild


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Carburetor rebuild
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Soon I’ll be rebuilding my Quick Fuel 750.  It’s a 4150 type with mechanical secondaries and no choke.  It’s been 20 years since I’ve done this.  Any tips/tricks or anyone willing to sacrifice a weekend afternoon to help out?  I’ll buy beverages and whip up something on the grill if it comes to an in person deal.



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In today’s digital world, don’t be afraid to embrace some analog.  My father tells me I was born 30 years late.

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Gavin H. Otsego



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I can help.

Any issues or drive ability problems? 



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Bob W.

Lino Lakes



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What is the particular issue with it, that you are rebuilding it for ?
Most often the metering block, main body and base plate passages can be cleaned with an aerosol spray can of carb cleaner and blown dry with an air hose. After that, it is simply replacing any dried out gaskets, accelerator pump diaphragms and power valves, if equipt with them.
When setting the needle and seat, I always set it a little lower than what the spec is, so it doesn't flood if slightly too high. Then adjust with the engine running, if you want maximum capacity.

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Mitch D.   River Falls, WI

Lifetime member of the "Cars apart Club"

Some Assembly Required

1966 Chevelle SS 396 M20

1970 Chevelle SS 396 M20

1967 Camaro SS/RS 350 M20



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Well, as documented here last summer, I had a starter issue.  The ignition was off and the starter kept cranking.  I’m pretty sure it caused gasket damage as I now have a fuel stain on my intake that wasn’t there before.  I noticed it before the October cruise the club did to Hutchinson.  It probably doesn’t need a full rebuild, but, as long as it’s coming off of the car for gasket replacement I was thinking of just rebuilding it anyway.



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In today’s digital world, don’t be afraid to embrace some analog.  My father tells me I was born 30 years late.

 1968 Malibu

Gavin H. Otsego



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Bobs_Place wrote:

I can help.

Any issues or drive ability problems? 


 No, just fuel stains on the intake.  Likely only needs new gaskets, but I figured as long as I have it off the car, may as well rebuild it.  I have the kit sitting on my workbench 



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In today’s digital world, don’t be afraid to embrace some analog.  My father tells me I was born 30 years late.

 1968 Malibu

Gavin H. Otsego



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Check the tightness of the four float bowl screws. I've had a couple of Holley's loosen up on their own, and it's the same design on the QF carb. 

Tightening them up solved the issue and no leaks. 



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Stan S.-Twin Cities 'South Metro'

1972 Malibu Convertible 2nd time around 

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There are several places that old gaskets/orings could cause leaks, I don't see how the starter problem could cause any leaks however.

If the carb still has fuel in it, set it on a piece of cardboard, you may be able to identify the leak.



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Bob W.

Lino Lakes



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SShink wrote:

Check the tightness of the four float bowl screws. I've had a couple of Holley's loosen up on their own, and it's the same design on the QF carb. 

Tightening them up solved the issue and no leaks. 


 I will do that first.



__________________

In today’s digital world, don’t be afraid to embrace some analog.  My father tells me I was born 30 years late.

 1968 Malibu

Gavin H. Otsego



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Bobs_Place wrote:

There are several places that old gaskets/orings could cause leaks, I don't see how the starter problem could cause any leaks however.

If the carb still has fuel in it, set it on a piece of cardboard, you may be able to identify the leak.


 The carb is dry.  I figured since the engine was cranking and no throttle was applied, the bowls got overfilled and caused gasket breakage.  I also could be way off.  I haven’t wrenched on old cars in 15 years, since I sold my Cougar, same car I rebuilt the carb on 20 years back.  If I’m way off base, let me know.  I’d love to not have to do it.  The carburetor isn’t that old.  4-5 years maybe.  It had only been on the car 1 summer before I bought it 3 years ago.



__________________

In today’s digital world, don’t be afraid to embrace some analog.  My father tells me I was born 30 years late.

 1968 Malibu

Gavin H. Otsego



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When you say the carb is dry, do you mean there is no fuel on the outside of the carb or the fuel bowl is dry/no fuel in the carb.

The float closes the needle and seat when fuel level is up, similar to the float in a toilet bowl.

If the bowl/s is overflowing than high float level, N&S or N&S oring and or fuel percolating in the bowl, all can cause fuel to spill over when sitting than run out the throttle shaft.

Has the carb been sitting for a long time?



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Bob W.

Lino Lakes



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Bobs_Place wrote:

When you say the carb is dry, do you mean there is no fuel on the outside of the carb or the fuel bowl is dry/no fuel in the carb.

The float closes the needle and seat when fuel level is up, similar to the float in a toilet bowl.

If the bowl/s is overflowing than high float level, N&S or N&S oring and or fuel percolating in the bowl, all can cause fuel to spill over when sitting than run out the throttle shaft.

Has the carb been sitting for a long time?


 The carb is dry, as in no fuel in the bowls and the outside is also dry, last I checked.  Car has been sitting since the first snow last October.  If I don’t need to tear into it, all the better.  I do plan on cleaning the intake and seeing if it’s still leaking after I check to see if the screws that hold the bowls in place have backed out.  As far as the fuel I run goes, it’s always ethanol free premium from Kwik Trip or Holiday.  I have never run corn fuel in it.



__________________

In today’s digital world, don’t be afraid to embrace some analog.  My father tells me I was born 30 years late.

 1968 Malibu

Gavin H. Otsego



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Honestly, a fuel stain on the intake from a Holley, who owns QF, is as common as the sun coming up in the morning. I think you will find a little turning of the bowl screws will suffice to stop the seepage.
As Bob said, if you have an overflow issue, it's the needle/seat not shutting off the fuel, which IS another common issue with these carbs. It doesn't take much to prevent the needle from seating. Another reason I leave the floats a little low. If the needle doesn't seat properly, the rising fuel level will put more pressure on the needle to overcome the tip not centering exactly and push it in.
Good to know you don't run corn squeezin's thru it. That can cause a whole 'nother set of issues.

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Mitch D.   River Falls, WI

Lifetime member of the "Cars apart Club"

Some Assembly Required

1966 Chevelle SS 396 M20

1970 Chevelle SS 396 M20

1967 Camaro SS/RS 350 M20



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Posts: 161
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So, I’m going to just check the bowl screws, clean the intake with gumout, and call it good for now. Having the rebuild kit is like having an ace up my sleeve. If I need it, it’s there. Thank you all for the advice! Looking forward to seeing some of you at the meetings this summer!

__________________

In today’s digital world, don’t be afraid to embrace some analog.  My father tells me I was born 30 years late.

 1968 Malibu

Gavin H. Otsego

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