HELP! 911T Zenith Floats

99ctehan · 04-24-2006, 01:41 PM

Recently, I acquired a 911T with a pair of Zenith 3bbl carbs sitting atop the intake. After putting some fresh gas in the tank and turning the key, fuel shot out of the carb hat via the vents. I rebuilt one using a Porsche kit, cleaned the floats and replaced the needle valve. OK. The floats do float... in water, really well. When placed in fuel, 2mm sit above the fuel line before they begin to rise. Could the problem be anything other than the floats? Are they shot? Can they be coated to increase buoyancy? Are there any compatible floats from something more domestic (Ford, VW, etc.)?? Im used to wrecking yard scrounging and am not afraid to fabricate with a bit of guidance.. ideas?
Does anybody have extras I can purchase? HELP?! Please and thank you.

RSstop · 04-24-2006, 06:40 PM

Chris,
Besides the float valves, have you set float levels. How about fuel pressure?
Check this site for great zenith info:
http://www.gary.suggate.dsl.pipex.com/index.html
Lyn

99ctehan · 04-25-2006, 12:52 PM

Dear RSSTOP,
When I removed the needle valves, there were 3 copper crush washers between the body and the hex head of the valve. Upon installing the new valves, I included only a new single washer as to lower the shut off level... No success. I dont have a fuel pressure gage.. So I added a clamp to the rubber line, cutting off all fuel circulation. I then back it off just enough to have fuel flow.. my guess .5 psi or less. Nevertheless, fuel spills from the vent and into the bowls. I also checked the floats for air leaks... NONE!
What am I doing wrong?!? Oh and thanks for the web recommendation.

99ctehan · 04-27-2006, 03:58 PM

Well, had the carb hat off today. I cleaned the floats again and they moved just fine on their axis. Fuel will not stop. Will raising the needles help? Am I running into an angle problem? I called PMO, Mesa, Pelican and a couple of other porsche shops. They said if the floats did not leak air while submerged under water, they should be ok. No bubbles... Can the gas be coming from somewhere else? Check the photos... And please help before I take a sledge hammer to this thing.

Chris

99ctehan · 04-27-2006, 04:02 PM

Please, Dont let a good one go to waste...[img]

http://forums.pelicanparts.com/uploads7/Picture+2051146182566.jpg[/img]

RSstop · 04-27-2006, 05:35 PM

Chris,
You have a real geyser there! I wonder if this is why the previous owner gave up on it? The float valves are obviously not shutting off flow. I think it could be one of two things. The fuel pump has been replaced with a higher pressure unit and overpowering the float needle valves or the needle valves are incorrect length and/ or the shim stack is way off. I would take the top off, turn it upside down to check that the floats are contacting and bottoming the needle valve before they hit the top of the housing. They should only be a few degrees past level when they first contact the spring loaded needle. This is a rough setting. Once you stop the geyser then the final float level needs to be adjusted with a special tool that screws into the bottom of the bowl so you can view the level externally. If you have the original valves and shims, you might want to go back and try those until you figure out what is wrong. Thinner shims lower the needle valve and lower the float level. If the rough setting is close, then put a pressure gauge in the fuel line and make sure you are around 3 to 5 psi. The aftermarket grose needle valves require about 1 psi less pressure. Let me know if that helps. Sorry I don't have a chance to reply to Pelican that often.
Lyn

andycook · andycook's Garage

One of my carbs is doing the same exact thing. Keep us posted.

99ctehan · 05-04-2006, 12:27 PM

Well, phase 2.. I went out and bought a Holley fuel pressure regulator. It is a simple dial regulator and adjusts from .5 to 6 psi. I also spoke to a top fuel racing friend... He told me that the pivot arms look warped and are binding. As they drop, resistance increases exponentially. I decided to put a simple steel faucet drain screen on the bottom of the bowl to preclude the floats from dropping too far. I then added the new regulator, then set to .5psi. Want to take a guess what happened next? You bet, the lines blew behind the fuel tank!!! Too bad I didnt realize it until there was a 1 meter puddle under das auto. I will post again this weekend after I replace ALL of the lines.

99ctehan · 05-04-2006, 02:41 PM

OH! Thanks again RSstop and Andycook for your replies!!! Im happy for the input! Ill try all of your ideas... The previous owner was my dad and he has never worked on the 911... He drove it, parked it in a garage and 20 years later, here I am. Its probably not worth much but sentimentality goes a long way.

andycook · andycook's Garage

Chris,
Here is what I found on mine. I think! I replaced my big$$ billet fuel pressure regulater with a standard Holley type. Ran that into a Y-block, and Wallah!! No More overflowing! I think the other regulator, although it said 4 psi was in fact pushing way more than that. With the Holley one, I am able to start at next to nothing adn work my way up. All the way up to 5 psdi with no overflow.
I
I did notice that my passenger side carb is not spraying fuel when the accellerator is open, so I am ordering two new kits as soon as I finish typing this. I am 90% sure my problem is attributed to too much fuel pressure.

Keep us posted on what you find. I not 100% sure I am not missing something else as well. Best of luck to you.

As for the value of your car....n one can put $ value on sentiment!! Get it running and enjoy it. You'll feel amazing each time you do!

99ctehan · 05-13-2006, 04:26 PM

Well, the fuel lines have been replaced. We will see what the new regulator does. Its a Mr. Gasket 30$ jobbie. Hopefully the floats wont sink!

99ctehan · 05-14-2006, 03:14 PM

WINNER!
Mister Gasket saves the day! The floats float, the float bowls are full... Tha accelerator pump.. uh kind of work and I am thrilled!!
Hey fellas, thank you sooo much for all of the advice and assistance. I cant thank you enough!

rw7810 · rw7810's Garage

Chris - I would just get a good fuel pump that puts out about 3.5 - 5.0 psi and lose that $30 regulator. They have been known to start leaking and cause engine fires. Facet makes an interupter pump (#1105) that works well. It should be mounted in front by the tank. Check Pegasus racing website.