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Secondary Carb Leak
Posted by: Noel Felty ()
Date: June 29, 2017 09:51AM

Alright this is making me nuts. I have r-side secondary that drips fuel from the around the venturi cluster with engine off! Here is what I have done.

1. I rebuilt carb. I rebuilt all carbs 6 months ago and all of the others are working well. Jets 54 on secondaries.
2. Installed the ball check valve needle and seat from Clarks. I installed these on all carbs.
3. Float return spring installed, stiffer spring on accel pump installed.
4. Played with float height from 1-1/8 to 1-1/4. I think last time I even increased it to almost 1-5/16. Drop is 1-1/2
5. Cleaned air holes in venturi cluster, changed venturi cluster and gasket, tightened screws for venturi cluster.
6. Changed spring in fuel pump to one from a very old GM one I had lying around.
7. Left floats in water overnight and they never took on water. Copper floats by the way.
8. Have pushed air through carb inlet and pushed float up. The needle seats with no air passing.

Things I have not done.
1. Done a fuel pressure test.I'm getting a tester.

I was successful at the last venture by changing height to 1-5/16. It ran like a raped ape for the day and on my way back from SC i could tell it was back to its old tricks. Sure enough, shut the engine off and I can see fuel dripping from around the top of the venturi cluster into the bowl. I have insulators sandwiched between 2 base gaskets. Car is a 140 .060 over with an isky 280. I cannot revert to 2 carbs and eliminate secondaries. That is not an option, that would be like drinking diet Mountain Dew. Any help is appreciated. This not a time for a J3m rant on EFI. I know Ted and am a huge fan of his system, so please save your breath.

Noel Felty
Brevard, NC
1966 Corsa 140 Before

1966 Corsa After

1972 Ford f100

Corsa SC
NC Mountain Corvairs

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Re: Secondary Carb Leak
Posted by: MattNall ()
Date: June 29, 2017 09:59AM

Pressure test....after you get a gauge.... make sure that's the first thing you do next time

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
...............110-PG.................................................Webered-Turbo

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Re: Secondary Carb Leak
Posted by: Noel Felty ()
Date: June 29, 2017 10:02AM

Yup, I have to eat my words here on always doing the simple stuff first! Ha! I forgot to mention that car is 66 but the carbs and linkage are 65.

Noel Felty
Brevard, NC
1966 Corsa 140 Before

1966 Corsa After

1972 Ford f100

Corsa SC
NC Mountain Corvairs

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Re: Secondary Carb Leak
Posted by: BobV66Vair ()
Date: June 29, 2017 10:14AM

The accelerator pump should be disabled (rubber cup removed) on the secondary's. There are no passageways for the accelerator pump to flow into the venturi. Primaries have two tiny holes between the accelerator pump bowl and the venturi as well. They allow a drip of fuel. The secondary's just add fuel through the main jet. It is also possible you have a primary base and a primary venture cluster. The secondary base has no passages for the idle flow of fuel. If you got a primary mixed up it will cause fuel leakage. Helt's book shows the exact pictures of each and how to identify them. Ask me how I know this!

66RTVair
Oregon
1965 Corsa 140 stock
1966 Monza DP Racecar
1968 Monza Parts for now

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Re: Secondary Carb Leak
Posted by: Gregory_Miller ()
Date: June 29, 2017 10:17AM

I replaced my mechanical with a Facet electric down under by the tank due to many high pressure fuel issues. Another nice thing is after sitting for a while I can run the pump to re-fill the carbs before starting, eliminating a lot of cranking. I used the Clark's fuel pump bypass plate and dead fuel pump parts to sandwich it between for a stock look. I also found I had to Epoxy the pump rod hole shut in the old fuel pump to prevent oil from being slung up into the dummy pump and leaking out between the lower pump piece and the bypass plate, even with the rubber gasket in place. As always, your mileage may vary.
I had tried cutting the spring in the mechanical to reduce pump pressure with no real success. Electric pusher pump was a win win.

Greg Miller
Eugene, Oregon

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Re: Secondary Carb Leak
Posted by: Gregory_Miller ()
Date: June 29, 2017 10:19AM

Hmm. Bob, my 65 secondaries have accelerator pump discharge holes and I get 2 solid squirts out of them when I open them up. Some folks leave the cups off, but others have reported a flat spot when the secondaries start to open without them.

Greg Miller
Eugene, Oregon

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Re: Secondary Carb Leak
Posted by: BobV66Vair ()
Date: June 29, 2017 12:56PM

I am going through mine now, rebuilding according the Bob Helt's book. I'll report back about any flat spots.

66RTVair
Oregon
1965 Corsa 140 stock
1966 Monza DP Racecar
1968 Monza Parts for now

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Re: Secondary Carb Leak
Posted by: RobertC ()
Date: June 29, 2017 01:46PM

BobV66Vair Wrote:
-------------------------------------------------------
> The accelerator pump should be disabled (rubber
> cup removed) on the secondary's. There are no
> passageways for the accelerator pump to flow into
> the venturi.

This is not 100% true. Need to check Bob Helt's book for the definitive answer.

As stated by Gregory, 65 secondaries have a single accelerator pump discharge hole.

I do not remember / know about 66 or later secondaries...

GM "recommended" removing the accelerator pump cup in its rebuild instructions to "fix" the problem where customer's secondary butterfly shellached shut because of non-use / partial use / mal-adjusted linkage.

If the linkage is adjusted correctly and you occasionally open the secondaries, there is no problem.

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Re: Secondary Carb Leak
Posted by: Spectre ()
Date: June 29, 2017 03:13PM

I've had both '65 and '66 secondaries. Both had a pump shot when the cup was in place. I don't remember if it was 1 or 2 streams.

David Clamp


1965 Corsa convertible - 140 4spd/3.55/AM-FM

2013 Mustang GT convertible - 5.0, 6spd auto, Procharger i-1

2003 Miata SE - 6spd manual (wife's toy)

"Victory is mine!" - SG

Norman, OK

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Re: Secondary Carb Leak
Posted by: Noel Felty ()
Date: June 30, 2017 06:46AM

Noel Felty Wrote
----------------------
>>>>>>>Things I have not done.
>>>>>>>1. Done a fuel pressure test.I'm getting a tester.

2. Purchase Bob Helts book!

Noel Felty
Brevard, NC
1966 Corsa 140 Before

1966 Corsa After

1972 Ford f100

Corsa SC
NC Mountain Corvairs

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Re: Secondary Carb Leak
Posted by: Noel Felty ()
Date: July 01, 2017 05:42AM

Ok I'm an idiot. Fuel pressure from pump is between 6-7psi. I domt want to spend all day cutting pump spring and testing. Show me some photos of nifty fuel pressure regulator setups if you have some.

Noel Felty
Brevard, NC
1966 Corsa 140 Before

1966 Corsa After

1972 Ford f100

Corsa SC
NC Mountain Corvairs

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Re: Secondary Carb Leak
Posted by: Wagon Master ()
Date: July 01, 2017 06:30AM

It may just be me but the cutting of the fuel pump spring is WAY easier than making a safe install of a pressure regulator.

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Re: Secondary Carb Leak
Posted by: Noel Felty ()
Date: July 01, 2017 06:54AM

How much spring do you cut? I was gonna was gonna bend some and mount by filler cap.

Noel Felty
Brevard, NC
1966 Corsa 140 Before

1966 Corsa After

1972 Ford f100

Corsa SC
NC Mountain Corvairs

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Re: Secondary Carb Leak
Posted by: Wagon Master ()
Date: July 01, 2017 07:28AM

I'd start with a lil over one full coil off the big end.

Been aircooled since 1973
Northwest Ohio 45840

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Re: Secondary Carb Leak
Posted by: Noel Felty ()
Date: July 01, 2017 08:50AM

I meant bend some steel line.

Noel Felty
Brevard, NC
1966 Corsa 140 Before

1966 Corsa After

1972 Ford f100

Corsa SC
NC Mountain Corvairs

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Re: Secondary Carb Leak
Posted by: Bob Helt ()
Date: July 02, 2017 08:36PM

Noel said........

Sure enough, shut the engine off and I can see fuel dripping from around the top of the venturi cluster into the bowl


Bob responds.....

Noel, not to be picky but is this really what you mean?


The top of the cluster is where the main well air bleed is. The top is way above the siphon bleed and way above the cluster mounting platform. And way above the discharge arms.

Now if fuel is really coming out of the top of the cluster, The bowl fuel level is way way way too high. In operation and also with the engine OFF, the fuel level should be right at the cluster mouning platform and any dripping would normally be out of the cluster arms.

Also, how are you seeing fuel dripping into the bowl? That is closed off from your view when looking at the dripping. Do you mean the carb throat????


Bob Helt

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thumbs upRe: Secondary Carb Leak
Posted by: BobV66Vair ()
Date: July 02, 2017 11:47PM

Gregory_Miller Wrote:
-------------------------------------------------------
> Hmm. Bob, my 65 secondaries have accelerator pump
> discharge holes and I get 2 solid squirts out of
> them when I open them up. Some folks leave the
> cups off, but others have reported a flat spot
> when the secondaries start to open without them.


I just finished rebuilding the four carbs on my 65 this weekend. I took your advice and put the accelerator pump cups on all four. It runs well now with no stumble when actuating the secondary's. I have changed my position on secondary cups! Use them!! There are times when a book does not tell the whole story, if you don't read it correctly. tongue sticking out smiley Thanks to Steve Goodman at Rear Engine Specialists, Golden Colorado, for sending me a replacement secondary throttle plate. Saved the carb and as the great guy he is, charged me nothing. thumbs up

Now on to replacing the worn linkages. On order from VairFare. I am going to completely rebuild the Corsa, it will just take time and money. I have lots of one, not so much of the other. It's a fun hobby.

66RTVair
Oregon
1965 Corsa 140 stock
1966 Monza DP Racecar
1968 Monza Parts for now



Edited 1 time(s). Last edit at 07/28/2022 09:41PM by 1966-Corsa-GT-180.

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Re: Secondary Carb Leak
Posted by: cnicol ()
Date: July 03, 2017 05:44AM

Noel Felty Wrote:
-------------------------------------------------------
> How much spring do you cut? I was gonna was gonna
> bend some and mount by filler cap.

Craig replies:
Once the pressure gauge is installed, it's easy to cut the spring to reduce pressure. The last one I did required removal of two complete coils.


One thing more: You might consider installation of a fuel return line as found in turbos and late-lates. The return line bleeds-off all fuel pressure after the engine is turned off.

If I were you, I would start with reducing the fuel pressure and if that isn't enough, I would experiment by cracking a fuel line (capture fuel in a rag) to check the residual pressure theory.

Craig N. Coeur d'Alene ID.
66 Black Monza 4dr, 4.2L V8 49k
61 Seamist Jade Rampside 140 PG
65 Canadian Monza 4dr 110/PG 40k
66 Sprint Corsa convt - First car! Re-purchased 43 years later
2+2 gnatsuM 5691

+17 Tons of parts

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Re: Secondary Carb Leak
Posted by: Saxon ()
Date: July 26, 2022 06:11PM

I am having a similar problem. My symptoms are such:

At dusk and evening when the weather cools off to 65F, the car runs fine at partial and WOT, but once I shut the engine down after the 1 hr plus drive, the RH secondary drips fuel into the throat. The other 3 carbs are fine, no drip.

The fuel is slowly emanating from the clusters and the main well vent (tiny hole on horizontal surface).

On warmer days, 75F plus, the rpms do not return to idle when shifting or coming to a stop. I estimate 1500 plus. Also, the drip rate increases such that I have a shot glass full of fuel in the throat.

I performed the following to rule out things:

-Recleaned internal passages with cleaner spray, copper wire and compressed air..

-Double checked my float height and float drop, 1 1/8" and 1 9/16", respectively.

-Examined the inlet seat and needle for obstruction and free movement. Swapped in two new sets. Looked under magnifying glass to look for any unsmooth surfaces.

-Confirmed I had a gasket and good threads of male and female inlet seat and carb hole.

-Tested the floats for buoyancy.

-Confirmed that floats are moving freely once the carb is assembled. I tip the carb upside down and few times to hear the power valve and the floats bounce on at the ends of the range of motion.

-Swapped carb from a Club member who was kind enough to donate a spare secondary. I dunked, sprayed, copper wired small passages and blew with air. Put in new parts and did not use any parts from the previous leaking car.

-On the donor carb, I used a new needle and seat. On the chance of defects, I I replaced needle and inlet with ball check type. I found a burr on ball check which I removed, cleaned and checked with lip vacuum and blowing.

Of odd note: I did not get a secondary pump jet squirt in the problem carb when after the car was warmed from cold. I did however get a jet squirt when the car was dripping fuel into bowl at engine shutoff.

Am I to be a dusk and evening driver like a vampire or should I test the fuel pressure. I don't know how, but can learn on you tube. Any hints specific to the Corvair mechanical pump. When fuel pumps go bad, does the spring weaken and pressure increase. Also, Clarks states the ball check fuel seat takes 5 more lbs of pressure.

Northern CA
66 Monza Coupe 4-spd 140



Edited 1 time(s). Last edit at 07/26/2022 06:16PM by Saxon.

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Re: Secondary Carb Leak
Posted by: joelsplace ()
Date: July 26, 2022 09:56PM

Absolutely check the fuel pressure.
I wonder if the corner of the engine that carburetor is on is overheating?
Have you deflashed the heads?
Is the fresh air hose sealed?

Joel
Northlake, TX
5 Ultravans, 136 Corvairs and counting...

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