rochester carburetor single barrel monojet issues!!!! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

PA69C10 · 11-11-2012, 10:09 PM

I just rebuilt my monojet carb. Bolted it back up and fired up the truck and found the carb is leaking a fair amount of fuel on to the exhaust and intake manifold. and i cant figure what would cause the leak while running?
-Todd

PA69C10 · 11-12-2012, 05:19 AM

Bump
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Shyguy · 11-12-2012, 09:41 AM

Sounds like the float level is not set right.

flyingtim01 · 11-12-2012, 09:41 AM

Without knowing where it's leaking from, I'd say the first thing to check is your float level. I don't recall off the top of my head what it should be on a monojet, but the little paper that came with the kit should have a listing for it. Also, if you have the old black nitrophyl float in there, they absorb fuel and get heavy, swap it out for a brass replacement.

That is of course assuming that you scraped off all the old gasket material, replaced with new gaskets and all the bolts are tight.

PA69C10 · 11-12-2012, 10:39 AM

Im new with carbs how do adjust the float?
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68gmsee · 11-12-2012, 10:49 AM

On these mono's the gaskets won't cause the leak - but - as mentioned above the most common leaks are caused by fuel level overflow. The float is one reason and the needle valve seating is another. Inspect the needle valve and seat carefully.

There is one remote possibility that the fuel pump pressure can force fuel through the needle valve so if the above doesn't resolve the problem, you may need to check the fuel pressure.

68gmsee · 11-12-2012, 10:53 AM

Quote:

Originally Posted by PA69C10

Im new with carbs how do adjust the float?
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Man, how did you rebuild it? If you bought a kit, the instructions give you explicit instructions. If you don't have them there's a lot of info on the net. Here's a youtube video on it.

http://www.youtube.com/watch?v=Kj3igH-i7SU

PA69C10 · 11-14-2012, 07:58 AM

Thank you all for the input. It was the float level that needed to be adjusted. She is running nice and strong! Thanks agIn.
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Shyguy · 11-14-2012, 10:13 AM

Glad to hear that you got the problem solved.

edub981 · 03-21-2013, 01:08 PM

So I just rebuilt my 1 barrel rochester b and did not set the float level. If gas has gotten on the gasket, will that need to be replaced after I properly set the float? This is if course a new gasket from the rebuild kit... it has dried out now.
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Daner · 03-21-2013, 09:27 PM

The gasket should be fine as long as it isn't torn.

edub981 · 03-21-2013, 10:14 PM

Thanks Daner. I just got her started with no leaks. I need to adjust the idle intake as she dies when I dont have the throttle open just a little, its too cold to mess any more with it right now... but good news is that there are no leaks. Its the little victories, right?
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11-11-2012, 10:09 PM	#1
PA69C10 Registered User Join Date: Oct 2012 Location: Gettysburg,Pa Posts: 19	rochester carburetor single barrel monojet issues!!!! I just rebuilt my monojet carb. Bolted it back up and fired up the truck and found the carb is leaking a fair amount of fuel on to the exhaust and intake manifold. and i cant figure what would cause the leak while running? -Todd

11-12-2012, 05:19 AM	#2
PA69C10 Registered User Join Date: Oct 2012 Location: Gettysburg,Pa Posts: 19	Re: rochester carburetor single barrel monojet issues!!!! Bump Posted via Mobile Device

11-12-2012, 09:41 AM	#3
Shyguy Junior Member Join Date: Dec 2006 Location: Southeast Missouri Posts: 2,436	Re: rochester carburetor single barrel monojet issues!!!! Sounds like the float level is not set right. __________________ '67 Chevy C-20 short stepper - build complete, 454/SM-465. '75 C-30 Single Cab DRW-350 small block/NP-435. '77 GMC-6500 Dump Truck, 427 Tall Deck. '92 GMC K-3500 Duallie, 454/4L80E.

11-12-2012, 09:41 AM	#4
flyingtim01 Registered User Join Date: Apr 2011 Location: Clinton, CT Posts: 101	Re: rochester carburetor single barrel monojet issues!!!! Without knowing where it's leaking from, I'd say the first thing to check is your float level. I don't recall off the top of my head what it should be on a monojet, but the little paper that came with the kit should have a listing for it. Also, if you have the old black nitrophyl float in there, they absorb fuel and get heavy, swap it out for a brass replacement. That is of course assuming that you scraped off all the old gasket material, replaced with new gaskets and all the bolts are tight. __________________ 1971 Chevy K20 350/SM465/NP205

11-12-2012, 10:39 AM	#5
PA69C10 Registered User Join Date: Oct 2012 Location: Gettysburg,Pa Posts: 19	Re: rochester carburetor single barrel monojet issues!!!! Im new with carbs how do adjust the float? Posted via Mobile Device

11-12-2012, 10:49 AM	#6
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: rochester carburetor single barrel monojet issues!!!! On these mono's the gaskets won't cause the leak - but - as mentioned above the most common leaks are caused by fuel level overflow. The float is one reason and the needle valve seating is another. Inspect the needle valve and seat carefully. There is one remote possibility that the fuel pump pressure can force fuel through the needle valve so if the above doesn't resolve the problem, you may need to check the fuel pressure. __________________ 68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive...

11-14-2012, 07:58 AM	#8
PA69C10 Registered User Join Date: Oct 2012 Location: Gettysburg,Pa Posts: 19	Re: rochester carburetor single barrel monojet issues!!!! Thank you all for the input. It was the float level that needed to be adjusted. She is running nice and strong! Thanks agIn. Posted via Mobile Device

11-14-2012, 10:13 AM	#9
Shyguy Junior Member Join Date: Dec 2006 Location: Southeast Missouri Posts: 2,436	Re: rochester carburetor single barrel monojet issues!!!! Glad to hear that you got the problem solved. __________________ '67 Chevy C-20 short stepper - build complete, 454/SM-465. '75 C-30 Single Cab DRW-350 small block/NP-435. '77 GMC-6500 Dump Truck, 427 Tall Deck. '92 GMC K-3500 Duallie, 454/4L80E.

03-21-2013, 01:08 PM	#10
edub981 Registered User Join Date: Mar 2013 Location: Fort Collins, CO Posts: 19	Re: rochester carburetor single barrel monojet issues!!!! So I just rebuilt my 1 barrel rochester b and did not set the float level. If gas has gotten on the gasket, will that need to be replaced after I properly set the float? This is if course a new gasket from the rebuild kit... it has dried out now. Posted via Mobile Device

03-21-2013, 09:27 PM	#11
Daner Registered User Join Date: Sep 2011 Location: Wildrose, North Dakota Posts: 300	Re: rochester carburetor single barrel monojet issues!!!! The gasket should be fine as long as it isn't torn. __________________ Dane 67 Chevy Fleet 250/4 speed 1/2 ton 68 Chevy 250/4 speed 1/2 ton for parts 49 GMC Grain truck 235 1 1/2 ton 76 Chevy 350/4 speed 1/2 ton

03-21-2013, 10:14 PM	#12
edub981 Registered User Join Date: Mar 2013 Location: Fort Collins, CO Posts: 19	Re: rochester carburetor single barrel monojet issues!!!! Thanks Daner. I just got her started with no leaks. I need to adjust the idle intake as she dies when I dont have the throttle open just a little, its too cold to mess any more with it right now... but good news is that there are no leaks. Its the little victories, right? Posted via Mobile Device



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