I have been battling with lean running conditions based on my plug readings. Many on the site suggested my stock calibrated Quadrajet was likely not jetted rich enough for ethanol gas. I just filled the tank with ethanol free gas and there is a noticable increase in power. The tip in response has always been good, but what's really noticable is the power after initial throttle. The gain feels like the same increase I got on my 2015 mustang gt after installing the cold air intake which K&N advertised as 20 hp. Kind of spendy for the gas, so I will probably re-jet my carb.

 

I've never experienced that kind of change.

 

If it's 8.5:1 or so, there's not enough compression to take advantage of the ethanol.

 

The reason that the carb should be re-jetted a step or two richer, is that ethanol has less heat content per gallon than pure gasoline.
These carbs were originally jetted for pure gasoline.
If you mix 10 percent ethanol with gasoline the mixture has less heat content than pure gasoline.
You must jet the carb slightly richer to make up for the loss of heat content to make the most power.
Otherwise, the fuel mixture will be too lean.

 

Mine is likely 9.5:1. 70 stock replacement pistons with Felpro gaskets. The carb is a 73 455 numbers matching stock calibrated according to the manufacturer.

 

Yeah.i have had a bit more run time on the good gas and there is definitely a difference. I accidentally smoked the tires a couple times and I drive the car often enough for.this not to happen and to notice a difference.

 

Keep putting the 100% gasoline in it. It will benifit you in the long run. Qjets are harder to tune when alcohol is involved.

 

I agree, if it’s available, use it.
All we have here is E-10 so I have no choice.

 

It is pretty well proven that straight gasoline will deliver better fuel economy than ethanol laced fuel.
Whether the increased fuel economy makes up for the higher price, depends on the difference in price.

 

It's aboUt 20% more. $6.40/gal vs $5.40/gal. In WA State. there are other advantages from what I have read. Ethanol and running lean is not really good for your engine. And the performance definitely puts a smile on my face. There is a 0.35 mile stretch on a back country straight away I use as a testing ground. I can usually get the car up to about 107 to 110 when it's running right. I buried the speedometer on the same length of road tonight.

 

Is running E85 an option? If you're going to rejet the carburetor it might be worth looking into...

 

At $6.40/gal for ethanol free, I may re-jet and buy 10% ethanol gas. E85 85% ethanol is not an option.

 

If you jetted a carb to run on E 85 you would have to jet it way rich.
Too rich to run E 10 at all.
That means that your travels would be limited to areas where E 85 was available.

 

Few years back, my original fuel pump went out about same time I noticed gas cap seal turned gummy. I blame ethanol.
RV90 ethanol free is what I run in lawn tractors and before my 68 goes into hibernation. $1.50 more than 92 unleaded.

Mader
omy442

 

is it possible to tune a Q-Jet for E85?

 

I wouldn't if it were possible.

 

At my current timing settings my BBO pings on 91 non ethanol and doesn't ping on 93 ethanol.... (93 non ethanol isn't available anywhere around me)

 

We don't drive these cars because they're cheap. Stick with the ethanol-free.
Octane boost?

 

I do, I have a whole lot less in my car compared to a new one, it's just as reliable and more fun. We have both ethanol and ethanol free 91 here locally, I use both. I miss the 93 ethanol (not available locally) that the car has run on for the last 12 years. I had to drop the timing a bit to run the 91.

 

I thought racers used E85 because it has a high octane rating? I don't see any reason a Qjet couldn't be tuned for E85. Of course, it's beside the point if it's not available locally.

 

I think you would also need very high compression ratio to take advantage of the E-85.

 

Living in South Carolina now, I'm now able to run Ethanol Free gas in all the old cars now all the time, from my 1996 Cutlass Supreme on down. I noticed an immediate difference in smoothness, especially my 3.4 1994 Cutlass. I specifically had the dualjet in the blue 79 Calais rebuilt to run on ethanol free only, big improvement.

The only drawback is the octane is 87. Not much more is needed around here since the stations selling ethanol free gas are really catering to the boating crowd of which there is alot of here. Occasionally I'll throw in some Lucas Octane Booster in the 79 Hurst Olds or the 94 Cutlass. The other cars are such low horsepower/low compression cars that using Octane Booster is not worth it.

 

Here 87 is 10% ethanol, 89 is about half as much, mixed Premium and Regular at the pumps. All our Premium is ethanol free, most is 91, finding 93 is almost impossible here. I use 91 only in my boat, flush the pump lines into the Challenger or Dakota. Do the same for anything the sits for months my pressure washer for example, along with STP additive. I have been using on 91 in my 70S which is $6.88 CAD per US gallon currently, it was over the $7 mark this Summer!

 

Check out this site.
Pure-gas.org

 

Apparently not all ethanol free gas is created equal. The first tank I filled about 18 gallons with 92 octane ethanol free from Chevron, although the pump said it was not a Chevron product. After about 1/2 a tank, I topped it off with 92 octane ethanol free at Safeway thinking gas from the same blue pump was likely from the same company as Chevron, but the car did not perform as well and there was considerable pinging at higher RPM. There was no pinging from the gas I got at Chevron. I typically only buy my gas from top tier stations and will continue to do so whether it be ethanol free or not.

 

It is also depending on how of the Premium a station moves. Fuel loses octane as it sits, the fresher the better.

 

And that makes sense. The Chevron may get more business from people willing to spend mr on fuel