carb theory

So Cal Mark · Post by **So Cal Mark** » Tue Apr 10, 2007 11:27 pm

I found this article in Engine Builder magazine concerning carburetors with todays' fuel. I'll quote since I'm not sure if the article is online
"Fuels have changed. Modern fuels are no longer designed for carbs, but for EFI. It makes a difference. The most important change I know of is the lowering of the boiling point. Simply put, fuel now has a lower boiling point than it used to. This results in float bowls drying out and harder starting. It cause accelerator pumps to fail when the fuel and additives and wet/dry cycles destroy the pump cups. It causes vapor locking, overheating and detonation from lean mixtures. You may be surprised to learn that the engine you are building FAILED because of these thing and now you are going to put the same accessory parts and carb on without curing the problems! You should be able to see what's coming"

This was written by Doc Frohmader at Engine Builder. It may just be that the carb setup you were running when the car was new is now all wrong

pertyfly · Post by **pertyfly** » Wed Apr 11, 2007 4:56 pm

... ... ... So what is there to do about this? Does this mean carbs cannot be used properly anymore, or they must be adjusted differently? Or is there an additive or something that can be used?

Chris

So Cal Mark · Post by **So Cal Mark** » Wed Apr 11, 2007 6:04 pm

at the very least I would say it means that rejetting to get proper mixture is probably needed

racydave · Post by **racydave** » Wed Apr 11, 2007 6:35 pm

The fuel boils easier, and boils inside the carb when hot. Also the addition of Ethanol to gas worstens the situation. I wonder if sometimes fuel lines will rust and cause a air pocket in the line on the suction side? I have my interrior out, and replaced my fuel lines. They had enough rust spots to cause a problem on top of the floorboard towards the front.. I bought bulk steel line and made it one piece, the 5/16 was a b to bend. Also going to repair the water leak at left upper cowl.

manoa matt · Post by **manoa matt** » Thu Apr 12, 2007 8:54 pm

Here in Hawaii we are having problems with the new fuel E-10 I think its called wich means its 10% Ethanol, Alcohol made from corn. Boaters are having the bigest problems. The alcohol eats up the fiberglass gas tanks for starters. Then the alcohol softens and eventually eats the rubber gas lines. Alcohol, like brake fluid is hydroscopic, which means it absorbes water. If it absorbes a little water its ok, thats what its supposed to do. But with a boat on the ocean, the alcohol absorbes alot of water and the engine eventually sputters out. One guy actually had to paddle with his hands back to shore. The alcohol also loostens up and partially disolves any gunk in the tank and lines. The gunk then flows thru the lines to the carb and then you have to clean the carb. Many lawn mover shops here have bee swamped with mowers that have gunked up carbs. The rubber fuel lines in Fuel injected cars don't seem to be affected as much, considering the lines are tougher to deal with higher pressures.

The good news is that several boat harbors still carry the old 89 gas, I just don't know if I can fill up my carbed Fiat there also.

Matt

So Cal Mark · Post by **So Cal Mark** » Thu Apr 12, 2007 11:16 pm

seal it up so it floats and call it an Amphibicar!

mdrburchette · Post by **mdrburchette** » Fri Apr 13, 2007 6:03 am

This sounds familiar. Is this the same gas we were forced to use in the late 80's during the winter months to curb pollution until they found it didn't help?