Do you use premium unleaded in your 350?

[Mister-B]

Just bought a '69 with a rebuilt 350 V8. The tank was almost empty, so I put 91 octane premium unleaded in. Now, it seems like I'm running a bit lean. It's a little harder to start than usual, but I'm not sure if it could also be due to the colder weather.

Should I run premium or not? Should I adjust anything since it is getting colder?
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[PAWS 72]

I don't know how it is there but we have ethanol in our gas here so I do run premium in mine.Plus my nissan and toyota.Seems mine runs better and gas mileage sucks any way.

[Square_78]

I run 94 in mine. Seems to start easier when cold, and also smoother at full throttle

[GMCJOE]

You need to run the gas with out the ethanol crap in it. It's not the fact you are running a higher octane, as in that 10% or whatever it is ethanol doesn't take the heat from the intake all that well. Mine runs great off it, but if it sits for a few after I shut it down hot it takes a few to get it cranked back up. The ethanol blended fuels like to boil in the carbs a lot quicker than the non blended. Especially if you running a damn Edelbrock 600. There is a phenolic spacer you can run, insulate the fuel lines, and such... That should help. It's the next step on mine engine wise when I swap my cam and carb out.

On adjustments, you should adjust your carb seasonal for best performance. I could be the above reason or both. Hell, I could just be talking out my butt. But most of this research has came from my problems with starting after hot and related to my 1406 Edelbrock.

[68gmsee]

Octane determines the rate of combustion. The higher the rating the slower the combustion. Unless your engine is specifically designed for higher octane there really is no need to use it. Colder weather will cause the harder to start issues but you could play with the timing a bit to see if it helps, otherwise, I'd go back to what you know the engine likes.

Don't forget that a lot of companies change their blending of fuel depending on the time of year so you may also be experiencing that. You may also be able to adjust the timing and idle air mixture to compensate .

[Hubscrub]

all my vehicles run good on 87 it just depends on how it's built, probably help if gas was actually gas too lol

[oklalawnboy]

Originally Posted by 68gmsee

Octane determines the rate of combustion. The higher the rating the slower the combustion. Unless your engine is specifically designed for higher octane there really is no need to use it. Colder weather will cause the harder to start issues but you could play with the timing a bit to see if it helps, otherwise, I'd go back to what you know the engine likes.

Don't forget that a lot of companies change their blending of fuel depending on the time of year so you may also be experiencing that. You may also be able to adjust the timing and idle air mixture to compensate .

X2 on the higher octane being harder to ignite. If your not running high compression you don't need premium.

[Square_78]

i dont even think you can buy unblended gas where i live. It all says 10% ethanol.

[special-K]

I run regular in mine. Don't notice any difference with hi-test,except it costs more. All gas around here is ethanol. If you live where there's a choice,enjoy it while you can. I don't expect it to last. It's just like when unleaded became the only choice. There were areas that still offered a choice,but only for a while.

[cdowns]

have you done anything to maintain the engine like change the fuel filter or air filter latly// most lo compression loperformance engines there is no advantage to running hitest other than putting more money in the pockets of the gasstation owners

[Fldawg]

Had a chemist come to our shop the other day to have a talk about today's fuels we are running and he said something very interesting if your not running over 10.5 to 1 compression on your engine, your wasting money running anything over 87 octane, so i tried it and found no differance with gas milege or performance, but i do run the non ethenol gas now it

[RenoKeene]

Originally Posted by Fldawg

Had a chemist come to our shop the other day to have a talk about today's fuels we are running and he said something very interesting if your not running over 10.5 to 1 compression on your engine, your wasting money running anything over 87 octane, so i tried it and found no differance with gas milege or performance, but i do run the non ethenol gas now it

Hey Dawg, sent you a PM. Who carrys non-ethenol in FL?

[Fldawg]

Originally Posted by RenoKeene

Hey Dawg, sent you a PM. Who carrys non-ethenol in FL?

we have about 6 stations here in panama city that carry non ethenol fuel, plus my friends parts house handles the racing fuel in town, but that's just for special occasions

[biggestjohn]

As others have noted, higher octane does not improve mileage.
I'm pretty sure the EPA mandates 10% ethanol, and they are pushing for 15%.
I know around Indiana, they also used to add 15% Liquefied Natural Gas to increase the octane, but I can't say for sure that they still do this.

[GMCJOE]

It is becoming more hard to find fuel that isn't blended with the 10%, that is for sure. Still a few around the town I am right now.

[DT1]

Here's an interesting read on Octane.
http://www.ftc.gov/bcp/edu/pubs/cons...tos/aut12.shtm

[PanelDeland]

Cat pee is cat pee.The ethanol just makes it worse.

[blackdawn]

lol wow i think this thread got off track. for a stock 350 87 should be fine, ethonal or not (forced to run it in cali anyway) you just need to have your carb adjusted. at the beginning of winter and at the beginning of summer as the temps change is when you have to do it.

[domeier]

Octane rating does not determine rate of combustion, it only determines how much pressure the fuel can be subjected to before it self ignites, (detonates.) Higher octane fuel is necessary in high compression engines only to prevent pre-ignition of the mixture. It won't provide any benefit to a low compression (8.5-9/1) stock 350.

[69GWC]

Like was said early, your compression. Ratio will decide which octane you need to run and iff its not over 10.1 you are more then likely. Fine on 87 oct.
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[ChevLoRay]

Where I live, there's one station that sells unblended gasoline. It is done to cater to the boating community. At the same time, it is better for outdoor equipment (mowers, chain saws, etc.) to run ethanol-free gasoline. This is the first season that I have done that. It has made a big difference. The ethanol attracts moisture, contaminating the gas in that equipment with water. Here's another: the ethanol attracted squirrels to the gas tank on my Honda mower...squirrels chewed a hole in the tank to get to the fuel. Since I went to unblended gas, no more problems with squirrels.

Now, for the issue: the first '69 C-10 I bought was back in '99. It had a hot little 350, that also had a TH350 behind it. That truck would bark the tires everytime it made the 1-2 shift, if you had the least amount of foot in the throttle. It would run on, when you shut off the ignition. It took premium gas to keep it from running-on, or from pinging under acceleration. On the other hand, my '69 (bought 6 months later), also equipped with a 350/TH400 would run fine on regular. This was before ethanol got to be the big issue it is today.

I find that I get better fuel economy when using the unblended gas, i.e., no ethanol. Ethanol may be good fodder for the politcos, but using corn to make ethanol, takes it out of the food chain to feed the meat and dairy industry, driving up the cost of feed that they do use. I realize that this is an entirely new topic, but that's my opinion. I know corn farmers are benefiting from ethanol, but we pay for it.

If your engine runs-on without premium, and it shuts down without dieseling when you use premium, then you should consider your options. If it doesn't ping, or run-on when you run ethanol, then that is your answer.

[GMCJOE]

lol... I would think you would have had no more squirrel problems after they got a sip of the fuel. That gave me a chuck.

[Fldawg]

i'm gonna end this tread by saying this:

PUT CORN ON MY TABLE NOT IN MY GASTANK

[Stocker]

Well the thread didn't end just yet. I have always run 87 octane in my virtually stock 350, with almost no issues.

I found that when hauling a cord of green hardwood up the mountain in warmer weather, the truck had spark knock (detonation, pinging, pre-ignition, whatever you like to call it). With three tanks, I just made sure I had premium fuel in one of them. A quick switch before heading up the mountain, no more spark knock.

[Critter]

Originally Posted by domeier

Octane rating does not determine rate of combustion, it only determines how much pressure the fuel can be subjected to before it self ignites, (detonates.) Higher octane fuel is necessary in high compression engines only to prevent pre-ignition of the mixture. It won't provide any benefit to a low compression (8.5-9/1) stock 350.

That is exactly correct. In fact, lower octane fuels provide higher mpgs. In simple terms there is more BTUs/gallon in a gallon of 85 octane than there is in 97. I have experienced this first hand when going from 85 octane in Wyoming and Colorado and then into the 87+ that we have in Texas

Originally Posted by Stocker

Well the thread didn't end just yet. I have always run 87 octane in my virtually stock 350, with almost no issues.

I found that when hauling a cord of green hardwood up the mountain in warmer weather, the truck had spark knock (detonation, pinging, pre-ignition, whatever you like to call it). With three tanks, I just made sure I had premium fuel in one of them. A quick switch before heading up the mountain, no more spark knock.

That sounds like you might need to adjust your timing a bit.