Gasoline Quality

[Timothy B.]

Sunday afternoon I took my 67 convertible for a two hour ride, the outside temps were approx 80-82* and the day was beautiful. After driving a while, I noticed a slight stumble after pressing the throttle like trying to accelerate in forth gear.

Long story short the problem got worse after stopping with heat soak and when I returned home after removing the air cleaner working the accelerator pump by hand the gas flow out of the pump squirters was very poor. The gasoline was boiling in the accelerator pump as it's near to the intake manifold plenum. This is the first time I have experenced this as my car never runs hot, the gasoline quality must really be getting bad.

I wonder how much ethonal is in the pump 91 octane, my gas is 87 octane and never had a problem before.

[Edward J.]

Re: Gasoline Quality

Tim, I think that the ethanol content is 10 percent, that is the most I believe at the pumps. unless there is lesser amounts in different states.

[Kenneth B.]

Re: Gasoline Quality

Sunday afternoon I took my 67 convertible for a two hour ride, the outside temps were approx 80-82* and the day was beautiful. After driving a while, I noticed a slight stumble after pressing the throttle like trying to accelerate in forth gear.

Long story short the problem got worse after stopping with heat soak and when I returned home after removing the air cleaner working the accelerator pump by hand the gas flow out of the pump squirters was very poor. The gasoline was boiling in the accelerator pump as it's near to the intake manifold plenum. This is the first time I have experenced this as my car never runs hot, the gasoline quality must really be getting bad.

I wonder how much ethonal is in the pump 91 octane, my gas is 87 octane and never had a problem before.

Was the gas the winter or summer mix. I think they change summer to winter. Not like the old days when gas was gas & you could get 101 octain & it didn't matter what the temp was. Blame the goverment & tree huggers for this. Iguess its for emisions & fuel mi.

[Timothy B.]

Re: Gasoline Quality

I don't know how to tell if the gasoline is winter or summer grade. My thoughts are that maybe a better grade of gasoline may have < 10% ethonal.

There may come a time that one of those long heat shields under the carburetor is needed to keep the heat off the float bowls.

[Clem Z.]

Re: Gasoline Quality

this is why GM had these holley heat shields to keep the heat off of the float bowls

[Clem Z.]

Re: Gasoline Quality

GM had one for the Q jet also

[William B.]

Re: Gasoline Quality

Are GM heat shields available anymore? Aftermarket? Shipping my '67 to Florida for the winter so they might be a good idea down there. Thanks

[Gene M.]

Re: Gasoline Quality

Ken, block off the exhaust heat passage thru the intake manifold will help. Ya may need to reset the choke a bit so it opens soon enough.

Corn juice just does not belong in our Vettes...........

[Joe L.]

Re: Gasoline Quality

Are GM heat shields available anymore? Aftermarket? Shipping my '67 to Florida for the winter so they might be a good idea down there. Thanks

William------


GM still has the shield available for Q-Jet applications although not under the original part number.

The shield for Holley applications is no longer available from GM but is available, I believe, from one of the "muscle car" reproduction parts companies.

[Joe L.]

Re: Gasoline Quality

I don't know how to tell if the gasoline is winter or summer grade. My thoughts are that maybe a better grade of gasoline may have < 10% ethonal.

There may come a time that one of those long heat shields under the carburetor is needed to keep the heat off the float bowls.

Tim-----

Except for E85, gasoline cannot contain more than 10% ethanol. There's talk about going to 15% but that would not be approved for use in any cars currently on the road.

[John D.]

Re: Gasoline Quality

Joe, Tom Barr, (the team leader one) told me that some of AZ has 15% ethanol. John

[Kurt G.]

Re: Gasoline Quality

Federal law requires the posting of ethanol content of 10% or higher. However, the refiner can put 9.999% ethanol in and never post it. As for Arizona, the fuel there is listed to contain MBPE (methyl-butyl-poly-ether) as an emission "cleaner" to help reduce visible emissions (smog). This being said, I'm not a mechanic, but it sounds like you may have other problems than gas. With the ambient temps you were discribing I'm not sure it was hot enough to cause boil-off.

[Michael W.]

Re: Gasoline Quality

As of July 2012, there was a grand total of ONE gas station in all of North America that sells E15

http://green.autoblog.com/2012/07/12/e15-now-available-at-one-lone-gas-station-in-kansas/

[Michael H.]

Re: Gasoline Quality

Sunday afternoon I took my 67 convertible for a two hour ride, the outside temps were approx 80-82* and the day was beautiful. After driving a while, I noticed a slight stumble after pressing the throttle like trying to accelerate in forth gear.

.

Timothy,

The issue that you describe is common when using ethanol of near 10%. Ethanol fuel will run around one or two jet sizes leaner than non-ethanol and this will cause the hesitation/flat spot. It will also cause many other issues that many have encountered in the last few years.
The problem may be worse with one season or the other depending on the seasonal mix of the fuel.

[Kurt G.]

Re: Gasoline Quality

One other thing to consider. In the last couple of decades, thanks to our beloved EPA most of the stuff that was in the gas our cars were built to on, you know, the stuff that burns, has been removed. What is left, along with the alcohol, has a lower vapor point..that will also cause the hesitation you are talking about. Although your car may not need it I would recommend you run premium in the car. It should help, but until we can get benzine, butane and propane back in the gas, we can only settle for poor performance