carburetors

[Buster]

I had a Holley 4160 650 cfm carb on my engine when I started it. It started loading up shortly after engine was started up maybe 3 weeks after. Got around to find out why and the gasket on rear bowl had desolved where metering plate mounts to body of carb. I used high test fuel 93% to crank engine and still have some in tank. I the asked place where I got the gasoline from if it had ethanol in it, they said yes. Can ethanol destroy these gaskets in carb, and how is this corrected to stop this problem.
At least I think that is what did it.

 

[ellis8500]

Just about all gasoline sold in the US has some ethanol in it; that's what replaced tetraethyl-lead as the octane enhancer. Higher octane fuel usually has more ethanol than a lower octane fuel. Depending on the age of your carb, ethanol might have affected the gasket material. Also, if your carb had been sitting dry for a long time, that too can destroy gaskets. Any new gaskets you buy should be OK with today's fuels.

 

[Mike]

I've never seen a gasket dissolve under ethanol use. :shrug2: I suppose anything can happen, however. Was this a brand-new carb? If it was, I would give Holley a call and talk to them about it. If it was something someone had rebuilt, I'm betting they didn't have the proper clutch-head driver to remove the metering plate screws and the carb cleaner attacked the gasket.

As Mr. Bill has pointed out, nearly everyone is selling non-stick, coated gaskets these days. The coating should protect the gasket from chemical attack.

 

[Buster]

Carb was new just a older one . It had the old cork style gaskets still in it. I took the carb apart and rebuilt with new gaskets paper style and replaced it. Engine running good now.

 

[Screaming Metal]

Some Gaskets don't the Ethanol......most are OK. Theres really no problem with the gaskets, its the RUBBER COMPONENTS and sometimes, in the way older cars the needlevalves.

Sorry, but I was in the field back in the 70's and when that 1st big gas crunch, WE found out eactly how those rubberized cork impregnated crapola gaskets cause alot of cars to quit running period. All the planets were in alignment then!

 

[Francis Blake]

Several years ago Chrysler stated they would not stand by their warrentee if ethanol was used in their cars because it would dissolve the o rings in the injectors. Strange that alcohol will dissolve something that gasoline won't.

 

[ellis8500]

The effect of solvent on "something" has to do with the chemical nature of the two. Solvents are classed as either polar or non-polar. A polar solvent is one that has an unbalanced electric charge characteristic; i.e., the molecule has a negative charged end and an opposite positive charged end. Non-polar solvents carry a neutral charge; i.e., no plus, no minus. Polar solvents work best on polar molecules. So alcohol, which is polar, works on polar molecules in the gasket. Petroleum based chemicals such as gasoline are non-polar so the work well dissolving other non-polar molecules.

When developing gasket materials one wants a polar material gasket with non-polar liquids; non-polar gaskets with polar liquids. Examples: petro grease is non-polar; polar water doesn't affect it much. Elastomer gasket materials are made of polar material; they tend to hold a static charge. They are not effected by non-polar liquids.

This is a simplified explanation. The chemistry is more complex but the above does explain why water, gasoline, alcohol, etc. dissolve some things and not others.