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Old 05-06-2024, 05:33 PM
Goatracer1 Goatracer1 is offline
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Default center carb flooding

First of all please read carefully. I have a center carb that floods over on the FIRST start up after the car has been sitting for a few days. After that the carb is fine until the car is parked and left again. Once the problem has corrected itself it will not happen again no matter how many times the car is started. This set up has been on several engines over the 30+ years that I have had it with no problems. It sat for several years before I put it on this basically stock 389 a year ago so before installing it I replaced the needles/seats and accelerator pumps and cleaned everything. Last year it ran fine. I thought maybe the float drop was too much and when the gas dried up in the bowl the needle valve would stick down so I limited the drop a little. I also lowered the float level a tiny bit. No help. This only happens on the FIRST start after being parked. There is NO gas in the float. The car has a stock replacement fuel pump from AMES and no back up electric pump. Thanks for any help.

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Old 05-06-2024, 06:14 PM
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Well it’s 100% has to be something with the float or the needle hanging up now for some reason since it did not have this issue last year and your other two carbs are fine even though they are not passing any fuel at idle, there just sitting there with full fuel bowls.

Why don’t you swap the needle and around from the center carb into one of the end ones and see what takes place.

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Old 05-06-2024, 07:21 PM
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And swap the float also.

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Old 05-06-2024, 11:24 PM
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Worth a try.

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Old 05-07-2024, 04:49 AM
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What year of center carb?

1965 center uses a smaller float than in the end carbs, also all end carbs uses .086" inlet valves w/o pull clip.

1965 center uses a .101" inlet valve and 1966 center uses a .120" inlet valve.
With original style brass floats the needle pull clip needs to be correctly mounted in float arm to avoid binding of needle.

I always use the correct size and original style inlet valves to avoid problems in the fuel inlet system.

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Old 05-07-2024, 10:40 AM
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1965 carb. I ordered the correct n/s and assumed it was correct.

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Old 05-19-2024, 12:19 PM
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Steve's suggestion is a good one. Swap one of the end carb floats and needle/seats to the center carb. Even though the center carb is smaller, the float and needle/seat will fit. Seat sizes and float size do not matter for troubleshooting.

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Old 05-19-2024, 02:38 PM
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What Steve and Dick said but put the n/s in 1 end carb and the float in the other and see if the problem follows.

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Old 05-19-2024, 08:27 PM
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Quote:
Originally Posted by Kenth View Post
What year of center carb?

1965 center uses a smaller float than in the end carbs, also all end carbs uses .086" inlet valves w/o pull clip.

1965 center uses a .101" inlet valve and 1966 center uses a .120" inlet valve.
With original style brass floats the needle pull clip needs to be correctly mounted in float arm to avoid binding of needle.

I always use the correct size and original style inlet valves to avoid problems in the fuel inlet system.
The smaller center carb used until 1965 will accommodate the larger floats used in the end carbs. This gives the center carb a higher tolerance for excessive fuel pressure (above 5-6 psi)

I suspect that NO ONE uses the .101" inlet valve or the .086": inlet valve on the center and end carbs, unless that is what is supplied in the rebuild kit.

The clip to pull the needle out of the seat is not needed on any center or end carb. The chances of this clip interfering with proper inlet valve operation make it a liability to proper operation. This also applies to Quadrajets.

For many years, I tested brass floats for leakage on every Tri-Power I rebuilt. The failure rate of these 60 year old floats is not good. I use nitrile floats today in all rebuilds and have not had a problem with them. Rochester eliminated brass floats in 1968.

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Old 05-19-2024, 10:36 PM
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I damaged the carb top to body gasket so I had to get a kit for the gasket. The kit came with a replacement for the needle and seat that used a replacement for the needle that was not a needle but a cylinder that had a soft material on the end to seal the seat. The instructions said it sealed better so I decided to try it. It worked! The N/S that I removed looked fine and was only a year old. Go figure.

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Old 05-20-2024, 06:28 AM
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Quote:
Originally Posted by Dick Boneske View Post
The smaller center carb used until 1965 will accommodate the larger floats used in the end carbs. This gives the center carb a higher tolerance for excessive fuel pressure (above 5-6 psi)

I suspect that NO ONE uses the .101" inlet valve or the .086": inlet valve on the center and end carbs, unless that is what is supplied in the rebuild kit.

The clip to pull the needle out of the seat is not needed on any center or end carb. The chances of this clip interfering with proper inlet valve operation make it a liability to proper operation. This also applies to Quadrajets.

For many years, I tested brass floats for leakage on every Tri-Power I rebuilt. The failure rate of these 60 year old floats is not good. I use nitrile floats today in all rebuilds and have not had a problem with them. Rochester eliminated brass floats in 1968.
I like to do and use stuff factory style.
They knew what to do and why.
There are vendors carrying the correct style and size inlet valves, just donīt count on finding them in commercial renew kits.
The pull clip wonīt hurt anything if correctly monted in the right application, and that is the issue.
Putting a large float in a small bowl WILL alter calibration and reduce fuel capacity, nothing i would do.
Not saying mickey mouse solutions wonīt work but i donīt like them.

FWIW

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Old 05-20-2024, 07:21 AM
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The correct orifice fuel valves DO come in our kits.

Like Kenth, I am not a fan of placing the large float in the center carb, as it significantly reduces the fuel volume in the center carb.

If the float were bad or the fuel valve were bad, the condition would be constant, not intermittant with only the first start.

TOTALLY GUESSING HERE:

All of us are aware that modern fuel evaporates relatively quickly, and leaves a sticky residue. What many may not know is that the same fuel is a wonderful solvent, and fresh fuel will dissolve a lot of stuff. We have seen a number of occurrances where the float will stick either on the float hanger portion of the airhorn casting, or the float pin itsself; creating flooding. As the fuel, once in the bowl, will dissolve the "evidence", this condition is difficult to detect. One test that may or may not make this determination is to allow the vehicle to sit unstarted for a time longer than normal, then fill the bowls of the carbs through the bowl vents and allowing to sit for an hour prior to attempting the start.

If the flooding does not occur, SOMETHING is sticking, and the "glue" dissolved by the fresh fuel.

If the flooding still occurs, then ?????

I think Goatracer called some time ago, and I may have not remembered the above for our conversation.

Along with the above, if using a diaphragm type fuel pump, residue will accumulate on a diaphragm. The diaphragm will flex slightly more if pumping against zero resistance (dry carburetor bowl), and flakes of residue will be dislodged, and move forward, POSSIBLY lodging under the carburetor fuel valve. Again, totally guessing, but issues I have seen. This issue is why we advocate filling the carburetor bowl(s) BEFORE starting when a new or rebuilt (dry) carburetor is installed on an engine.

EDIT: reread everything, and just saw the comments about brass floats. Dick, we are experiencing a totally different result than you. The float on every carb with a brass float that I have ever built has been tested, plus every carb we junk we test the brass float and keep it if good. Other than the large cylindrically floats with the fuel valve running through the center of the float (discontinued in 1930), we are finding less than one bad float in a hundred. Now the new currently produced "brass" floats from "somewhere" use something generally referred to as "solder" that is incompatible with modern fuel. No comments on the phenolic floats, other than if a brass float is available, we would not use a phenolic one. And if the customer demanded a phenolic float, we would tactfully suggest that he/she should use a different rebuilder.

Jon

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Last edited by carbking; 05-20-2024 at 07:31 AM.
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Old 05-20-2024, 08:17 AM
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I forget if there is a tab on the float to control drop distance,

perhaps after sitting for a period the bowl dries up float drops down far enough to cock something and stick then after running the bowl is full enough for this not to happen

a new inlet may be built slightly different for this not to happen, just a thought

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Old 05-20-2024, 01:07 PM
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There is a tab for float drop. The factory service manual says a float drop of at least 1&3/4 inches but not enough to cause the needle to stick. I checked that right away and even lessened it. The car is a Bonneville so performance is not of great importance. I always check my floats and have over the years only found a couple of leaky brass floats which I repaired. I have however found several of the solid floats that were absorbing gas. The residue idea makes sense because the problem only occurred when the car had been sitting long enough to evaporate the fuel. Would adding a fuel stabilizer like STABUL (?) help? Hopefully the problem is gone.

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Old 05-20-2024, 08:43 PM
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There are some folks that swear by Sta-bil, others that swear at it!

The glaciers will again cover southern California (there is a cliche here, think about it) before I would consider using it again!

As to the brass floats (I got called away from the forum when I was posting my last post):

On "modern" (1931 and newer) floats virtually all that we found with leaks leaked at the solder seam. The older cylindrical floats I mentioned were spun. The spinning created a hardening of the brass, and if the floats were not annealed, they would, over time, develop vertical "fatigue" cracks. I have yet to solve this issue. Even my Dad, who taught me to solder, could not fix the vertical fatigue cracks, and Dad was good! In that case, find a company with metal spinning capabilities, and have new ones made.

There is a solution to new brass floats, and I have mentioned it here before. Rochester did NOT make the brass floats, just like they farm out the foam floats. There are two companies that I believe are still in business here in the USA that make floats; decades ago, we bought 1000's of floats from them. But at the time, they had a 1000 line item minimum. At my age, I am not going to invest that kind of money in brass floats for a 1000 each of two floats. Maybe some of you younger whippersnappers might consider it. They actually have tooling for many (would like to say most) brass floats clear back to the 1930's.

Jon

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If you truly believe that "one size fits all" try walking a mile in your spouse's shoes!

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Current caretaker of the remains of Stromberg Caburetor, and custodian of the existing Carter and Kingston carburetor drawings.
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Old 05-21-2024, 12:37 PM
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Sorry to disagree, but there are other considerations about the floats. Rochester changed from brass to phenolic floats in 1968 or 1969. Quadrajets also switched to phenolic floats about the same time. As I said, I use phenolic floats and have not had a single failure with hundreds of carbs rebuilt. I have, however had multiple failures of OEM brass floats, even though I test them all before assy. A few customers have requested brass floats, which I accomodate.

Regarding the small center carb float bowl capacity, I strongly suggest you compare the float bowl size of the larege 2G vs. the small 2GC. They are virtually identical. Using a large 2G float in the small 2GC will cause no problem with the carb's operation.

Please consider that the statements I've made about floats, needle/seats are based on experience I've had with hundreds of Tri-Power rebuilds. I understand your desire to maintain factory components and settings, but sometimes, we are able to improve on what was designed 60+ years ago.

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Old 05-21-2024, 03:55 PM
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Quadrajets has always used phenolic/nitrophyl floats from factory.

FWIW

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Old 05-21-2024, 04:13 PM
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We're ignoring the most common problem today with Tri-Powers--excessive fuel pressure. Fuel pumps for our Pontiacs, including those branded AC, those from Ames, and nearly all from auto parts stores, far exceed 6 psi, which is the maximum pressure a Rochester 2 barrel carb can handle. Some users have opted to add a fuel pressure regulator, some switched to an electric fuel pump that can be adjusted to deliver 6 psi or less. While these solutions work, I prefer to retain the mechanical fuel pump.

I know of a person on the east coast who sells rebuild kits for mechanical fuel pumps. He is, however, not a friendly, helpful soul. If you know of someone who has the knowledge and access to parts needed, I believe that info would be valuable to many Tri-Power users.

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Old 05-26-2024, 08:44 AM
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There is a gentleman on the east coast (Tom Hannaford, owner of "Then & Now Automotive") who is exceptionally knowledgable concerning fuel pumps. He does rebuild them as well, AND he manufactures the parts. He is also as friendly as anyone who does telephone orders, and exceptionally helpful. Tom's biggest problem IS the above statement. Because of his knowledge and ability he is busier than "a long-tailed cat in a room full of rocking chairs" (thank you Tennessee Ernie) and therefore sometimes difficult to contact. Patience is a virtue here, as the difficulty in contact is worth the wait.

As for the foam floats, Rochester did not begin using the foam floats because of quality, rather cost, the same reason Rochester discontinued leather accelerator pumps in favor of neoprene. Carter and Stromberg continued using both leather accelerator pumps and brass floats. And Rochester carbs sold for less than the equivilent Carters and Strombergs.

Jon

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"Good carburetion is fuelish hot air".

"The most expensive carburetor is the wrong one given to you by your neighbor".

If you truly believe that "one size fits all" try walking a mile in your spouse's shoes!

Owner of The Carburetor Shop, LLC (of Missouri).

Current caretaker of the remains of Stromberg Caburetor, and custodian of the existing Carter and Kingston carburetor drawings.
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Old 05-26-2024, 05:32 PM
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Quote:
Originally Posted by carbking View Post
There is a gentleman on the east coast (Tom Hannaford, owner of "Then & Now Automotive") who is exceptionally knowledgable concerning fuel pumps. He does rebuild them as well, AND he manufactures the parts. He is also as friendly as anyone who does telephone orders, and exceptionally helpful. Tom's biggest problem IS the above statement. Because of his knowledge and ability he is busier than "a long-tailed cat in a room full of rocking chairs" (thank you Tennessee Ernie) and therefore sometimes difficult to contact. Patience is a virtue here, as the difficulty in contact is worth the wait.

As for the foam floats, Rochester did not begin using the foam floats because of quality, rather cost, the same reason Rochester discontinued leather accelerator pumps in favor of neoprene. Carter and Stromberg continued using both leather accelerator pumps and brass floats. And Rochester carbs sold for less than the equivilent Carters and Strombergs.

Jon
My point is--I've never had a problem with nitrile floats. I have seen dozens of failures of brass floats. Maybe this one cost-saving idea actually improved Rochester carbs?

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