Buoyancy of carb floats in ethanol gas - Ford Muscle Forums : Ford Muscle Cars Tech Forum
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post #1 of 21 (permalink) Old 09-24-2012, 12:04 PM Thread Starter
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Buoyancy of carb floats in ethanol gas

At a car show recently and discussing carbs with another '64 Galaxie owner. He said that the buoyancy of the copper/brass floats in the carb aren't as buoyant in ethanol gas. He recommended changing the floats to plastic ones. He was saying the floats ride low and cause the fuel to over flow. Anyone else hear anything of this? It is first i'd heard of it.



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post #2 of 21 (permalink) Old 09-24-2012, 12:28 PM
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Re: Buoyancy of carb floats in ethanol gas

Quote:
He said that the buoyancy of the copper/brass floats in the carb aren't as buoyant in ethanol gas.
IMO

I never liked brass floats as the seam would deteriorate over time and take on fuel, leading to sinking. Preferred phenolic floats and these had to be checked regularly (using weigh scale). Generally, when a card was overhauled (shop environment) a new float(s) was accepted practice.

I think the new material to deal with methanol is nitrophyl.

As for brass float bob-weight in a fuel solution, Mr. Peabody (aka Dave) will have to answer that one...

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post #3 of 21 (permalink) Old 09-24-2012, 02:50 PM
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Re: Buoyancy of carb floats in ethanol gas

YES!! With 1960's gasoline the carburetor wet level should be 29/64ths (FSM) from the top of the carb bowl.. With today's 10% ethanol it needs to between 57 /128ths and 115/256ths. Simple arithmetic.

Putts drives a 1965 customized Galaxie. Rebuilt 390, 4100 electric choke on a Performer, MX, AC, PS, PB w Scarebird front discs on Cragar 17" S/S.
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post #4 of 21 (permalink) Old 09-24-2012, 08:32 PM
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Re: Buoyancy of carb floats in ethanol gas

LOL. Are you shimming your float height with pubic hairs Putts?

I haven't seen Mr. Peabody around, but I do know that the assumption is not true. In-fact, gasoline is less dense than ethanol, and so the greater the percentage of ethanol in gasoline, the higher your float will sit, and therefore the lower your actual fuel level. How's that for goofy?

I think the confusion is that ethanol has lower energy density, but has higher mass (weight) per gallon. I don't have the numbers off the top of my head, but it's a very tiny amount of difference between gasoline and any typical gasohol. Something like .001% density difference for every 1% of added ethanol. Nearly immeasurable for the purposes of float height. Ignore it.

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post #5 of 21 (permalink) Old 09-24-2012, 08:57 PM
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Re: Buoyancy of carb floats in ethanol gas

He must have one hell of a set of graduated scales...

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post #6 of 21 (permalink) Old 09-25-2012, 07:51 AM
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Re: Buoyancy of carb floats in ethanol gas

Damn I LOVE Putt's measuring! No wonder he beat me at golf last year!

I thought he was 3/32" closer to the hole giving me the go-ahead putt, but he insisted that I was 4.39/397th's away thus giving him the go ahead putt for the win...
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post #7 of 21 (permalink) Old 09-25-2012, 09:58 AM
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Re: Buoyancy of carb floats in ethanol gas

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Originally Posted by FEandGoingBroke View Post
Damn I LOVE Putt's measuring! No wonder he beat me at golf last year!

I thought he was 3/32" closer to the hole giving me the go-ahead putt, but he insisted that I was 4.39/397th's away thus giving him the go ahead putt for the win...
Funny stuff!

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post #8 of 21 (permalink) Old 09-25-2012, 08:28 PM
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Re: Buoyancy of carb floats in ethanol gas

Ethanol's specific gravity is around .815
Gasoline's specific gravity varies roughly .680 to .730.

SO ethanol is denser (water is 1.00). That would make a normal float float higher in ethanol than in gasoline. Unless my thinking is incorrect (which wouldn't be the first time....)

The density variance in gasoline is also one reason a typical bracket car can vary ET's from one batch of fuel to another. Race fuel is kept tighter tolerance. Methanol is even tighter. Ethanol-who knows (never messed with it personally). Ethanol blends, E85, etc are not available here so there's no reason to. Besides Methanol is still cheap and very consistent; though not as consistent as Nitromethane, but we all know nitro isn't exactly easy on parts.

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post #9 of 21 (permalink) Old 09-26-2012, 04:35 AM
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Re: Buoyancy of carb floats in ethanol gas

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I think the confusion is that ethanol has lower energy density, but has higher mass (weight) per gallon. I don't have the numbers off the top of my head, but it's a very tiny amount of difference between gasoline and any typical gasohol. Something like .001% density difference for every 1% of added ethanol. Nearly immeasurable for the purposes of float height. Ignore it.

David
I wrote a big long post about energy density at some point, but I don't recall where.

As for the density, gasoline density varies so much from station to station anyways I wouldn't even worry about it. Ethanol IS more likely to corrode and pinhole a brass float though.

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post #10 of 21 (permalink) Old 09-26-2012, 09:58 AM
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Re: Buoyancy of carb floats in ethanol gas

How can ethanol corrode a brass float? Is it the amount of water it absorbs? Corrosion is the result of oxygen and water getting on the brass isn't it?
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post #11 of 21 (permalink) Old 09-26-2012, 11:01 AM
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Re: Buoyancy of carb floats in ethanol gas

Right. As a reminder, the ethanol in gasoline blends and the methanol used in racing and "gas dryers" are different animals. Methanol is far more absorbent and far more aggressive, so racer's have to take special precautions just to use it. Ethanol in our gas is not nearly so bad, but the most important step you can take is don't let it sit. The absorbed water isn't a biggie, unless you let it sit to absorb even more water, and then eat your parts. If you only use the car once in a while or store it, drain the system before storage, find a source of straight gas (like boat marinas, small airports and rural stations), or get an additive made for ethanol blends to fight the corrosion.

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post #12 of 21 (permalink) Old 09-26-2012, 07:05 PM
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Re: Buoyancy of carb floats in ethanol gas

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Methanol is far more absorbent and far more aggressive, so racer's have to take special precautions just to use it.
David

I guess I'm on borrowed time. 11 years now on the flying toilet and never had a single problem with anything. Tried changing the pill once. Put the one I took out back in.

Corrosiveness of methanol, IMO, is highly over-rated. Either that or I'm on borrowed time.

Only issue I EVER had with it was on a 12.5 HP briggs L-head, stock carb (running methanol...fixed jet drilled)-the carb was plastic. After several years of sitting with fuel in it the plastic got soft. But it still started & ran, just not very well. Pulled the bowl and immediately knew it was done. Put the bowl back on, ran the race (and won...easily), then mowed the grass the next day until it ran out of fuel...then scrapped it. I figure after it sat that long it wouldn't matter if it was gas, ethanol, E-85 or methanol....it wasn't going to work with any of them after sitting that long.

.....Have run meth in almost everything imaginable. Ethanol I am not familiar with personally. Other than it (blended with gasoline) earns me a paycheck.

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post #13 of 21 (permalink) Old 09-26-2012, 11:52 PM
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Re: Buoyancy of carb floats in ethanol gas

Yeah, it's not that bad either, but much more aggressive than ethanol. I know we would have some issue every race with the alky dragster if we didn't drain everything and flush some gas through it. The steel parts would seemingly rust overnight. Standard steel-core fuel injectors were trash if left for a week with the stuff in them. Same for the fuel cutoff on the Enderle setup. Electric pumps would be trash. Chances were, if it wasn't rated for methanol, you would have issues sooner or later.

One time we left the alky in the system because everyone thought somebody else flushed it. The next week, we found it in there and just ran it. Everything worked that time, but our trap was down 6-7 mph. A gravity test of the alky found it had absorbed enough water in the hot and humid summer weather to put us down on power. A quick change to fresh meth had it right back up to normal. I love the stuff, but it can be a PITA sometimes.

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post #14 of 21 (permalink) Old 09-27-2012, 04:51 AM
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Re: Buoyancy of carb floats in ethanol gas

In one of the race cars we ran E85 in an .035" Aluminum tank. After about 3 years we had a few pinholes here and there.

The main cause for the corrosivity of alcohols is the halide ions (chlorine mostly, with others like fluorine etc) Adding water to ethanol actually decreases corrosivity.
Most of it is just a byproduct of the production process supposedly - here's an SAE paper to that effect.

Chlorine is nasty because it strips the passivation layer off of aluminum so it corrodes more quickly. They can eat up copper/tin/lead too.

Course you can't just add water to your fuel tank if you want to go fast.

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post #15 of 21 (permalink) Old 09-27-2012, 06:04 AM
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Re: Buoyancy of carb floats in ethanol gas

Quote:
Originally Posted by FEandGoingBroke View Post
Damn I LOVE Putt's measuring! No wonder he beat me at golf last year!

I thought he was 3/32" closer to the hole giving me the go-ahead putt, but he insisted that I was 4.39/397th's away thus giving him the go ahead putt for the win...

When you're the Puttster you need to be accurate.

Puttster

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