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Old 09-08-2016, 07:21 PM   #1
stouchton
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Default Question about carb needle valve preference

Had the car out today, running well. Stopped and filled up the gas tank (below 1/4 up to full). First time tank has been full since rebuilding carb.

Well... car didn't want to run after filling tank, and took a little while to figure out she was flooding.

So, when I rebuilt the carb I used the needle valve included in the Renner rebuild kit. It appeared to be all metal, not a viton tipped valve like I am used to, and what I removed from carb. It also seemed to be more of a ball, not a cone. Has me thinking it might have more trouble sealing with a higher head of gas behind it?

Of course it might be dirt from the tank - but just wondering if there was a better choice for needle valve than what I have in there right now.
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Old 09-09-2016, 12:29 AM   #2
Flathead
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Default Re: Question about carb needle valve preference

Check for dirt or rust, I have heard that Renners stuff is good.
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Old 09-09-2016, 12:47 AM   #3
Mike V. Florida
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Default Re: Question about carb needle valve preference

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Check for dirt or rust, I have heard that Renners stuff is good.
What he said!
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Old 09-09-2016, 01:50 AM   #4
J Franklin
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Default Re: Question about carb needle valve preference

if internal gaskets are not tight it can be trouble. You can also shut of the fuel cock and when the engine starts to stumble open it and the rush of gas may flush debris off the seat if that is your problem. Any gravity feed system can loose gas from a faulty or unseated float valve or cracked float.
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Old 09-09-2016, 08:09 AM   #5
stouchton
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Default Re: Question about carb needle valve preference

Thanks guys - will pull her apart and check for dirt or rust.

I did shut the gas off, let her run out, then opened the gas back up but she soon flooded again.

Float is good, and did not have this issue with the viton cone style valve. Float seems fine.

Have noticed some rust particles in the glass sediment bowl - so maybe something is sneaking past.
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Old 09-09-2016, 08:24 AM   #6
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Default Re: Question about carb needle valve preference

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Check the arm on the float for a dimple where the back end of the float needle contacts the arm. The wear spot can at the contact spot can cause a bind. Sanding the edges to flare out the edges is the fix. There was a very recent post about this last week or so.
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Old 09-09-2016, 08:38 AM   #7
goodoldvic
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Default Re: Question about carb needle valve preference

I use the gross jet type needle/seat in carburetors. They work for me.
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Old 09-09-2016, 11:50 AM   #8
stouchton
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Default Re: Question about carb needle valve preference

Thanks - will check that contact spot.

Is the gross jet type the round ball style??
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Old 09-09-2016, 02:50 PM   #9
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Default Re: Question about carb needle valve preference

Yes the gross jet type has a metal or glass ball that seals against the seat. I have changed stock Zenith metal needle/seats and Viton seats on my Marvel to the ball style with much happiness.
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Old 09-10-2016, 12:54 PM   #10
Carb Guy
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Default Re: Question about carb needle valve preference

Biggest problem I have is no good float valves, not a good one on the market today, some work most don't.
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Old 09-19-2016, 10:27 AM   #11
stouchton
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Default Re: Question about carb needle valve preference

Well I'll be.... completely wrong about what was going on!!!

First - not a gross jet type - just a metal original style. I did put my viton back in.

And - she is not flooding, she has a vapor lock condition. Fuel is boiling in the carb.

First time she had an issue: Ran at about 45mph for about 20 minutes, shut down at gas station and when she restarted ran like crap. Cleared up after driving a few minutes, but recurred while idling in my driveway.

Second time - ran her out to the car show at Oley fair on Saturday. Got stuck in a line of traffic and basically idled for 10 minutes. Was backing into a parking place and she shut down. Would not restart. Ran fine 2 hours later.

Got home pondering the issue. Let her idle on my driveway for 10 minutes, she got rough and then quit. Removed one spark plug strap and let her arc to the strap. Good strong spark till engine quit running. Good spark while running rough. Did not think it was ignition. Installed the site tube on the carb. Fired her up. After 5 minutes fuel level started bobbling up an down, engine got rough, bubbles started coming up in site tube then she quit. Seems fuel is boiling in carb. PLEASE NOTE - hood was down - I was peaking in through the hood to watch the fuel.

Grabbed a stop watch and tried this a couple times - was like clockwork after 5 minutes it would happen. Opened hood and she idled 20 minutes no issue.

I did just rebuild the carb prior to this issue starting, and I did use the copper manifold gasket instead of the paper gasket. Besides the mixture possibly being different after rebuild (new jets) the only other difference is the gasket. Idle mixture should be close to the same - so I am going to replace the copper gasket and try again.

Also - had another thought. I have a thermostat installed, and the top of the radiator is hanging at about 185F. Thinking removing the thermostat may let her idle cooler.... Doubt this is the cause, she was fine before in a 4th of July parade idling for an hour in 95F weather.....
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Old 09-19-2016, 03:06 PM   #12
Tom Wesenberg
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Default Re: Question about carb needle valve preference

Here's from a thread I started on another car site. I installed this heat shield about 10 days ago, and it has made a world of difference. No more boiling fuel problems. Someone posted a picture of the nice heat shield they had made for their Model A, and it helped them with boiling fuel problems also. I'll be buying more of this stainless plate so I can make one for my Model A, just in case I get stuck with crap gas sometime.

Carb Heat Shield is a Big Help
In the 60's and 70's when my Studebakers were my only cars I never had fuel related problems, but today's gas boils at a lower temperature and has caused me problems with hot restarts and when the car sets for more than a couple days. If I stopped for a few minutes the heat would boil the fuel in the carb and I'd have to crank a lot to get the engine restarted. BTW, I only use the better gas without the corn crap, unless I'm far from home and can't find the good gas.

I made this heat shield from a thin sheet of stainless steel, and got it installed just in time to go on tour with the club last Saturday. This has made a big improvement in hot and cold restarts. Yesterday the 1950 Champion fired right up after setting since Saturday, and again it started right away after several short stops. Also notice the split white plastic tubing I slipped over the fuel line from the pump to the carb. I like white because it reflects the heat more than black.

The Tee fitting by the carb is a small copper line running to a low pressure gauge I hung off the bottom of the dash, so I can monitor fuel pressure until I'm sure everything is finally working right. I'll probably just leave it on until I reinstall my mechanical pump.



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Old 09-19-2016, 05:44 PM   #13
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Default Re: Question about carb needle valve preference

My solution for crap gas boiling in the carburetor:
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Old 09-19-2016, 07:00 PM   #14
Tom Wesenberg
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Default Re: Question about carb needle valve preference

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Originally Posted by Zener424 View Post
My solution for crap gas boiling in the carburetor:
Cool! Now you can tell people your Model A has a blower.

I wouldn't think the fan and heat sink would be needed, at least if you added a shield on the exhaust down pipe.
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Old 09-20-2016, 05:40 AM   #15
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Default Re: Question about carb needle valve preference

The fan and heat sink work very well when you are driving somewhere and you stop for a break. There is a switch under the dash. When I shut the engine down, I leave the fan on and it cools the carb down quickly, preventing the gas from boiling and enables a nice normal start when you get back in the car and start the engine back up again. The fan draws very little current.
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Old 09-20-2016, 12:53 PM   #16
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Default Re: Question about carb needle valve preference

Im no fan of E10 (AKA 'crap gas') but it gets blamed a lot for boiling/vapor lock issues when the real culprit is the individual RVP (Reid Vapor Pressure) of the specific fuel blend or refinery batch.

Any fuel blend should have a max RVP of about 8 or 9. Adding 10% ethanol raises that number about 1. Atmospheric pressure is about 15 so the fuel does not boil at normal temps if the RVP is below that number.

The real culprit is one of the other blend components- Butane. By itself it has an RVP of 52. It boils at 30F. Put more than 2% in a fuel blend and you will never get the RVP of the blend low enough to avoid boiling at high under-hood temps unless the system is pressurized well above the blend's RVP.

Butane is kind of a refinery white elephant- extremely little market and value. Refiners will try to dump as much as possible in the gas mix without exceeding allowable local RVP's or, lacking those local regulations, as much as possible without excessive tank boiling and overwhelming of modern vapor recovery systems. Some northern climate 'winter blends' may have so much butane they boil on a 60F day.

My suggestion: Try a different brand fuel, from a different refinery. Drain the offending stuff and use it in your modern with a pressurized fuel system. Unfortunately there are no simple RVP test kits like there are to measure % ethanol.
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Old 09-20-2016, 02:03 PM   #17
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Default Re: Question about carb needle valve preference

I've read your post #11 carefully. I am not seeing what you are seeing in the sight tube, so I may have this wrong. But please consider:

I think the float valve could be sticking in the closed position. When you let the car idle, the float comes all the way up, closes the valve, and in sticks in the closed position. Then when you burn all of the gas out of the bowl, the engine stumbles and stalls. Possibly what you are seeing in the sight tube is the fuel level splashing and bubbles resulting from the splashing just as the fuel level gets very low, just before the bowl runs dry.

Try letting the engine idle again, and as it starts to stumble, tap on the carb bowl in the area of the float valve and see if the engine recovers. Try it again, and as the engine stumbles, pull the choke a couple of times and see if the problem clears. Either of these could indicate a stuck float valve, and not boiling fuel.

Some of the new float valves just simply stick.

I may be completely wrong about your car, but this sounds similar to the symptoms my A suffered due to a sticking float valve.

W. Michael
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