10% Ethanol & Percolating Fuel???

[Tim S.]

Re: 10% Ethanol & Percolating Fuel???

Bill,
I can understand your frustration. Perhaps JD will chime in some more to correct my opinion if need be. It is my understanding, unleaded fuel lacks some lubrication qualities for the high pressure pump in your F.I. unit. That in addition to the difference in boiling point, makes race fuel a better choice. If you were to look in the archives, you will see aviation fuel is even more sought after!

It is unfortunate that this problem will only get worse with time. For my own use, I have started to purchase 55 gallon drums of leaded race fuel from the local lubricant and fuel distributor. While expensive, it yields the results.

Best Regards,
Tim

[Clem Z.]

Re: 10% Ethanol & Percolating Fuel???

I don't think Clem's idea would help. We discussed this hear before. It's not the hot oil causing the problem. It's a crap fuel. JD

you guys with a IR gun could check the difference in temp between the difference parts of the FI unit to see if the base plate is hotter than the rest of the system. since oil temp runs about 20+ degrees above the water temp the oil could be raising the FI unit above the engine temp. if that base plate is radiating heat into the "spider" cooling it down 20 degrees could help. BWTFDIKAFI

[Jack H.]

Re: 10% Ethanol & Percolating Fuel???

"It can't be that complicated can it?"

Additive to boost octane AND lower boiling point...

YES, it is that complicated because you're going in two different directions at once! The octane rating of gas is NOT a measure of 'power' or energy content. It's a measure of how consistently the fuel burns (basis is 100% octane) with different measurement techniques (Motors method, Research method). People often confuse what a fuel's octane rating is meant to convey and think it's the be-all/end-all yardstick for measuring fuel...

What Joe Lucia said is dead nuts on. You have a complex mixture of hydrocarbons in gasoline. Each has its own set of combustion and boiling characteristics. The addition of ethanol simply changes the composition of the fuel.

How does an additive prevent ethanol from behaving like ethanol? That's what's being suggested here. Some kind of snake oil that'll make the ethanol 'go away'.

You could build your own 'still' and re-refine. HEY, that's a joke...a VERY dangerous approach!

If one suffers a fuel percolation problem with today's ethanol doped pump gas, the best way to start addressing the problem is to look for methods to reduce the underhood temperature the carb's fuel bowl 'sees'.

Things like blocking the intake manifold's cross over plumbing, blinding the intake manifold's 'hot slot', making sure you have the right carb to intake mounting gasket (some factory setups used thick insulating gaskets, others used heat reflective metal shielding) and getting the right recepie for pump to carb fuel lines can help reduce heat at the carb considerably.

I've seen more than one 'driver' Corvette that was equipped with a plastic, in-line, external fuel filter and/or had the factory original steel fuel lines cut and replaced with rubber hose + clamps. When the engine is running, ONE way heat gets dissipated from the carb is via the fuel lines back to the frame (the frame is a HUGE heat sink)...

[Stuart F.]

Re: 10% Ethanol & Percolating Fuel???

Jack;

Just a small item for clarification; where and how does the steel fuel lines dissipate heat from the carb backl to the frame? or, what year Vette are you talking about?

On my 63 L-76, the fuel line from the pump to the filter is chrome plated steel. The filter mounts on the water manifold portion of the intake manifold (and is, I believe, the main source of the heat obsorbed by the fuel). The line to the carb is normally chrome plated steel as well. The steel fuel line from the tank is clipped to the frame, but the connection to the pump is by "flexible" rubber hose, i.e. I don't see the connection as to how the heat from the carb could be dissipated back to the frame.

I wanted to try and solve my problem without changing the stock underhood appearance, but once I'd jacked the carb up with a phonelic spacer I could not get my chromed steel fuel line to stretch between the filter and the carb. Using the hose itself made no measurable change/improvement in the amount of heat seen at the carb. Similarly, changing to the electric choke and eliminating the chromed hot air tube to it did not show any measurable improvement. There too, I didn't want to try and stretch that tube to fit either. The electric choke's main improvement came in it's operation as it controls both the closing and opening of the choke with the assist of the choke pull off. The slight hot air bleed through the air tube to the choke is insignificant as it only shows a draw of from 0.5 to 1.5 "hg.

In addition, I played around with the primary and secondary main jets, as well as accelerator pump squirting nozzles, different float settings (also Tomco valves in place of needle/seats), tried different venturi clusters to change air bleeds, and even different VAC cans & ignition timing (as they affect throttle plate position to the fuel transfer slots).

Bottom line, I finally found a combination that seems to work well with the crappy fuel. The only change I now make for the heat of the summer is to wire open my heat riser (I found it still works best unwired in the cooler months). I have both an F.I. spacer ready to replace the heat riser, and restricted manifold heat passage intake gaskets ready if the situation gets worse.

Stu Fox

[Gerard F.]

Re: 10% Ethanol & Percolating Fuel???

"It can't be that complicated can it?"

Jack,

I agree with your first statement above, but somewhat, about what follows.

On a carburated car, percolation is always a problem after shut down after a hot run in high temperature. It happened with the old gas as well as the new. But the new gas boils at a lower temperature. The problem only occurs when you shut down hot, therefore the heat rises to the top of the engine and then starts boiling things.

Here's a few things to consider:

1. If you have a vented gas cap, is it working? Sometimes they don't work. On a long run, the muffler heats up the gas tank creating pressure in the gas tank to fuel pump line. Enough to fill the carburetor bowl and more. Simple thing to do, would be to unscrew the gas cap after shutdown.

2. Someone, I think it was Clem, discussed drilling a hole in the fuel pump diaphram, so that on shutdown, the fuel drains back to the gas tank relieving pressure. The newer cars with the emissions cannister already do this, except the fuel flows from the carb bowl to the cannister.

3. Heat Soak or Percolation only occurs when things get hot. If you can keep the Carb bowls or FI unit cool when the engine is hot, it would pay off. Insulation gaskets would be great, and maybe someone will come up with a cooling fan just for the carb or FI unit.

But in the end, it is just the nature of the beast. Deal with it as best you can.

Jack, looking forward to the next road tour to San Jose, see you in Barstow. We will have plenty to discuss.

[Bill B.]

Re: 10% Ethanol & Percolating Fuel???

I have read that there is afoot legislation on the federal level to raise the ethanol from 10% to 15% in fuels at the pump. However I have contacted both Sunoco and ExxonMobil and they both responded with emails telling me that their trying to run cleaner fuels, but they have no plans to raise the ethanol level not have they been notified of any change in the different composition of Gasoline. But the EPA and California's CARB would like to change the make up of pump fuels.

Jim - Please keep us updated, I appreciate it Bill

[Bill B.]

Re: 10% Ethanol & Percolating Fuel???

Bill, Rather than type my extremely long answer again see Sept 21, 2008 by Clem Zahrobsky. "Keeping fuel injection cooler".
Or go above to search and type in "perculation" for a long list of suggestions. Let us know if you have gotten some good tips. John

John - Got it, and appreciate the location of the thread.

Bill

[Jim W.]

Re: 10% Ethanol & Percolating Fuel???

Jim - Please keep us updated, I appreciate it Bill

I promise I will. I got interested in this when Governor Tom Ridge and the EPA decided to wage war against each other over the 'New' federal emissions regulations. Our wonderful government has a habit of mandating things like Automobile fuels ingredients without the slightest announcement of any kind. Back then the EPA, and a host of environmental groups never ending political pressure to run cleaner fuels have made the gasoline sold today about 180 degrees opposed to the same fuel of only twenty years ago.

Back then, I worked for a local politician and had the opportunity to talk with Gov. Ridge about US, collector car enthusiast. We talked about the constant emissions regulations pending and I was able to prove that if you took all the collector cars, and started them all in one 24 hour period, the amount of pollution was negligible when compared with say a jet airplane or coal fired power plant and or all the everyday traffic. Governor Tom Ridge is a little bit of a 'Car guy' and he agreed and signed into pennsylvania law that if a car is driven less than 5000 miles a year, it is exempt from any emissions testing at all.

But all of us really need to stay current with the issues concerning our collector cars as the EPA and a whole host of greenies will not be satisfied till any and all of our corvettes are silenced. And they often attach, emissions regulations bills onto some amendments that have nothing to do with the environment.

[Joe C.]

Re: 10% Ethanol & Percolating Fuel???

I think that the most effective way to cool an intake manifold is to provide an air gap between it and the lifter gallery. There are some insulating (possibly phenolic) intake/plenum gaskets used by the ricers, but I have not been able to find any for V-8 engines. The primary reason that some intake manifolds were provided with a splash pan, was to prevent the oil splash from "coking" when exposed to the extreme heat of the exhaust crossover passage in the intake manifold. Intakes without exhaust crossover NEVER were provided with splash pans, because their purpose in that instance would be moot. The intake manifold, once in direct contact with the engine block, will quickly achieve the same temperature due to conduction, that's why an air gap is necessary.

I see merit in Bill's cool can idea, which has worked for years. Another idea worth trying would be to insulate the fuel lines. Finally, you should consider insulating coatings for the fuel carrying components of the fuel injection unit. These coatings are very effective in lowering temps when applied to combustion chambers and piston crowns.

I don't like the idea of painting the inside of any engine with varnish! Its usefulness might be marginal on a full race engine using a high volume oil pump, but certainly a waste of time on any engine using a standard volume pump.

[John D.]

Re: 10% Ethanol & Percolating Fuel???

Bill,
I can understand your frustration. Perhaps JD will chime in some more to correct my opinion if need be. It is my understanding, unleaded fuel lacks some lubrication qualities for the high pressure pump in your F.I. unit. That in addition to the difference in boiling point, makes race fuel a better choice. If you were to look in the archives, you will see aviation fuel is even more sought after!

It is unfortunate that this problem will only get worse with time. For my own use, I have started to purchase 55 gallon drums of leaded race fuel from the local lubricant and fuel distributor. While expensive, it yields the results.

Best Regards,
Tim

Tim, That is sooo untrue. Story: My father God bless him always preached to me to stay away from leaded fuel as all it does is make for a dirty engine. Don Baker preaches the same and makes fun of me cause I love 100LL aviation fuel. But I don't love it because of the lead. I like it because it will not gel in a 100 yrs.!!!! It boils at a much higher boiling point and it smells good. I have conducted tests using my own 63 FI car-the LWC and found I can run the engine for an hour at idle with the hood closed in 93 degree weather. Then turn the engine off. Wait 10 minutes and then put the pedal to the metal and turn the key and the car starts up and runs like a clock. Try that with ethanol. But I am off the track. Dad only used Amoco white gas. Never had lead & I am sure it never will. I have had a fuel car of some sort since 1961. Been playing with FI's since then too. All my fuel cars burned Amoco. (except one) I put boo coo miles on them. I am not knocking lead additives that guys sell. Just saying I never used lead period.
The high pressure pump made from 57 to 65 has sell lubricating carbon bushings. To quote Duke as I admire him, "Any brand will do".
Be careful using just racing fuel guys. Now most of you racers know a lot more than I do about it. I am sure most of you know that some of it contains corrosives that will eat out a carb fuel bowl as well as an FI fuel bowl. I see it a lot. Some racing fuels left set in a fuel bowl with eat right thru the damn thing. Happened on a 63 I restored. The guy left the car set for 2-1/2 years and then complained to me the fuel bowl was leaking. I was shocked when I took the unit apart again only to discover the bottom of the bowl was history. So was his wallet. JD

[Bruce B.]

Re: 10% Ethanol & Percolating Fuel???

I am using the full 1/8 inch gasket (per John DeGregory) under my 4360 FI unit and running 100LL avaition fuel and so far no perc or hot start problems. In Ohio it is now legal to purchase 100LL for other then avation use, so I have been told by the airport people.
A month ago it was $3.39 a gallon but now it is up to $4.00+.
In addition when on the road I use Shell gas, as in Ohio it does not contain ethanol.

[Clem Z.]

Re: 10% Ethanol & Percolating Fuel???

I am using the full 1/8 inch gasket (per John DeGregory) under my 4360 FI unit and running 100LL avaition fuel and so far no perc or hot start problems. In Ohio it is now legal to purchase 100LL for other then avation use, so I have been told by the airport people.
A month ago it was $3.39 a gallon but now it is up to $4.00+.
In addition when on the road I use Shell gas, as in Ohio it does not contain ethanol.

that full cover gasket may also shield the spider from the heat off of the baseplate

[Jack H.]

Re: 10% Ethanol & Percolating Fuel???

OK, the fuel pump IS connected to the frame rail lines via rubber hose. A solid inflexible line doesn't get it because there's engine cradle rock stress at work.

And, yes, rubber is a poor conductor of heat. But, think for a moment... What's inside the rubber?

Yep, the hose is filled with rather cool from the tank gasoline that's under the static pressure of hydrostatic head from the fuel tank. On either side of the rubber hose, the gasoline inside 'touches' the ID of the metal fuel lines to the tank AND the fuel pump body.

Bottom line, there IS a heat conduction path from the carb/engine to the frame, albeit imperfect...

[Clem Z.]

Re: 10% Ethanol & Percolating Fuel???

OK, the fuel pump IS connected to the frame rail lines via rubber hose. A solid inflexible line doesn't get it because there's engine cradle rock stress at work.

And, yes, rubber is a poor conductor of heat. But, think for a moment... What's inside the rubber?

Yep, the hose is filled with rather cool from the tank gasoline that's under the static pressure of hydrostatic head from the fuel tank. On either side of the rubber hose, the gasoline inside 'touches' the ID of the metal fuel lines to the tank AND the fuel pump body.

Bottom line, there IS a heat conduction path from the carb/engine to the frame, albeit imperfect...

on some race cars i tried using a small power steering cooler in the fuel line between the electric fuel pump and the carb by putting it out in the air stream. did it help i don't know but i am sure it did not hurt.

[Jack H.]

Re: 10% Ethanol & Percolating Fuel???

We've seen a couple of cars at the shop that had been modified in this area (jury rigged fuel line plumbing) that responded favorably when returned to factory stock.

But, it's a delicate thermo balance under the hood and the addition of ethanol definitely pushed things the wrong way! Typically, there's more than ONE single item to consider with each (fan, fan clutch, age/condition of radiator, radiator shroud, seals, carb gasket, fuel lines, Etc.) all having a little piece of the big picture...

So, you go one thing at a time and eventually you should get there!

Race cars DEFINATELY pose challenges. There, we're well outside the thermal envelope of the original design (more BTU generation under the hood + LOTS of other modifications). But, ethanol's boiling characteristics aren't typically an issue because most are running with top drawer race gas.

However, there IS a trend to use alchol because it's intrinsically higher in octane rating than gas. If I remember correctly, pure ethanol weighs in around 105 octane. But, you use a LOT more of it getting around the track...