1970 C3 LS5 ... Question about fuel

[Luke 1967]

I've used STA-BIL for my lawnmowers in the past, and it seemed to do the trick. However, when it comes to my 'precious old cars', I simply prefer not to take any chances. Fuel with no ethanol is better than ethanol in your fuel, and an additive to try to neutralize its effects. If its not too much trouble at this point to pump the fuel out, I would do that. If not STA-BIL is a good choice for stabilizer.

 

[Rruuff Day]

I've used STA-BIL for my lawnmowers in the past, and it seemed to do the trick. However, when it comes to my 'precious old cars', I simply prefer not to take any chances. Fuel with no ethanol is better than ethanol in your fuel, and an additive to try to neutralize its effects. If its not too much trouble at this point to pump the fuel out, I would do that. If not STA-BIL is a good choice for stabilizer.

Stabil does little to neutralize the effects of ethanol, even the formulations that claim they do. It is purely an additive to prevent the degradation of gasoline, which for pure gasoline begins to occur between three to six months. Gasoline with ethanol degrades somewhat faster, between two and three months.

 

[2KforeverC5]

Just bought the car about two months ago and I’ve been filling up with mostly Ultramar 91 octane, which as I understand contains ethanol.

This week is storage time, I'll be storing the car where it can also be looked at mechanically throughout the winter months. The car is in great shape, the only known issue (up until a couple of days ago) is that the steering needs attention. It gives me a hard time when trying to turn while at a dead stop and this will be addressed while in storage.

Anyway ....

Since I bought the car, I have been experiencing some “dieseling” (engine continues to run, cough and sputter when turned off) on a few occasions. This has happened a total of maybe five times in the relatively short time I've driven the car and this lasts about 5 seconds each time. After doing a bit of research, I decided to start using Shell 91 V-Power two days ago. So I pull into my local Shell and top-off a good half-tank worth of Shell 91 V-power. So now the gas tank is completely full (half Ultramar 91 and half Shell 91).

Took the car for a long drive and after turning the car off the engine keeps going, this time the dieseling is more intense, white smoke, some backfiring. This lasts a good 15 seconds (maybe more). So while this is going on, I turn the ignition on again. The engines resumes but at higher RPM. Can’t get the RPMs to come down. Stopped the engine in ‘drive' gear .... more dieseling.

After letting the car sit for a good 45 minutes, I re-start the car. Normal RPM by the sound of it. The tach is not hooked up because the previous owner had changed (upgraded) the ignition system and the stock tach cannot be hooked-up to the new distributor. This will be addressed during winter storage because it will require the removal of the dash.

My question is are the two issues related (the "dieseling" and the high RPM)?
Is (was) the use of the Ultramar gas the problem? Now that I've changed over to Shell VP 91 will the problem go away next spring?
Or, given the engine is of a higher compression, will this dieseling issue continue no matter what fuel I use (ethanol-free or not) and would octane booster be required going forward?

Could the problem be the ignition system itself? My neighbour tells me it may be too advanced (he drives a '68 Mustang). My mechanic tells me he checked the ignition and made sure it's where it's supposed to be, but he'll consider it again during the winter months while the car is in his care.

Thanks.

Just brotherly advice, refrain from using anything with ETHANOL. Specially during storage. Drain that staff off your vehicles.

 

[2KforeverC5]

Just bought the car about two months ago and I’ve been filling up with mostly Ultramar 91 octane, which as I understand contains ethanol.

This week is storage time, I'll be storing the car where it can also be looked at mechanically throughout the winter months. The car is in great shape, the only known issue (up until a couple of days ago) is that the steering needs attention. It gives me a hard time when trying to turn while at a dead stop and this will be addressed while in storage.

Anyway ....

Since I bought the car, I have been experiencing some “dieseling” (engine continues to run, cough and sputter when turned off) on a few occasions. This has happened a total of maybe five times in the relatively short time I've driven the car and this lasts about 5 seconds each time. After doing a bit of research, I decided to start using Shell 91 V-Power two days ago. So I pull into my local Shell and top-off a good half-tank worth of Shell 91 V-power. So now the gas tank is completely full (half Ultramar 91 and half Shell 91).

Took the car for a long drive and after turning the car off the engine keeps going, this time the dieseling is more intense, white smoke, some backfiring. This lasts a good 15 seconds (maybe more). So while this is going on, I turn the ignition on again. The engines resumes but at higher RPM. Can’t get the RPMs to come down. Stopped the engine in ‘drive' gear .... more dieseling.

After letting the car sit for a good 45 minutes, I re-start the car. Normal RPM by the sound of it. The tach is not hooked up because the previous owner had changed (upgraded) the ignition system and the stock tach cannot be hooked-up to the new distributor. This will be addressed during winter storage because it will require the removal of the dash.

My question is are the two issues related (the "dieseling" and the high RPM)?
Is (was) the use of the Ultramar gas the problem? Now that I've changed over to Shell VP 91 will the problem go away next spring?
Or, given the engine is of a higher compression, will this dieseling issue continue no matter what fuel I use (ethanol-free or not) and would octane booster be required going forward?

Could the problem be the ignition system itself? My neighbour tells me it may be too advanced (he drives a '68 Mustang). My mechanic tells me he checked the ignition and made sure it's where it's supposed to be, but he'll consider it again during the winter months while the car is in his care.

Thanks.

Hopefully, it’s not the fuel pump.

 

[2KforeverC5]

Stabil does little to neutralize the effects of ethanol, even the formulations that claim they do. It is purely an additive to prevent the degradation of gasoline, which for pure gasoline begins to occur between three to six months. Gasoline with ethanol degrades somewhat faster, between two and three months.

Yes. Moisture in your tank will mix with fuel. So ensure premium full tank specially during storage.

 

[Keith Tedford]

Just bought the car about two months ago and I’ve been filling up with mostly Ultramar 91 octane, which as I understand contains ethanol.

This week is storage time, I'll be storing the car where it can also be looked at mechanically throughout the winter months. The car is in great shape, the only known issue (up until a couple of days ago) is that the steering needs attention. It gives me a hard time when trying to turn while at a dead stop and this will be addressed while in storage.

Anyway ....

Since I bought the car, I have been experiencing some “dieseling” (engine continues to run, cough and sputter when turned off) on a few occasions. This has happened a total of maybe five times in the relatively short time I've driven the car and this lasts about 5 seconds each time. After doing a bit of research, I decided to start using Shell 91 V-Power two days ago. So I pull into my local Shell and top-off a good half-tank worth of Shell 91 V-power. So now the gas tank is completely full (half Ultramar 91 and half Shell 91).

Took the car for a long drive and after turning the car off the engine keeps going, this time the dieseling is more intense, white smoke, some backfiring. This lasts a good 15 seconds (maybe more). So while this is going on, I turn the ignition on again. The engines resumes but at higher RPM. Can’t get the RPMs to come down. Stopped the engine in ‘drive' gear .... more dieseling.

After letting the car sit for a good 45 minutes, I re-start the car. Normal RPM by the sound of it. The tach is not hooked up because the previous owner had changed (upgraded) the ignition system and the stock tach cannot be hooked-up to the new distributor. This will be addressed during winter storage because it will require the removal of the dash.

My question is are the two issues related (the "dieseling" and the high RPM)?
Is (was) the use of the Ultramar gas the problem? Now that I've changed over to Shell VP 91 will the problem go away next spring?
Or, given the engine is of a higher compression, will this dieseling issue continue no matter what fuel I use (ethanol-free or not) and would octane booster be required going forward?

Could the problem be the ignition system itself? My neighbour tells me it may be too advanced (he drives a '68 Mustang). My mechanic tells me he checked the ignition and made sure it's where it's supposed to be, but he'll consider it again during the winter months while the car is in his care.

Thanks.

Before we bought our 2005 Corvette in 2012, I had a 1969 SS396 Chevelle with the L78 engine and 11-1 compression. First, I blocked the heat riser open. Getting heat away from the incoming air charge was the big thing. I added the sheet metal heat shield that snaps in between the heads. I blocked off the intake heat crossover passage in the intake. I also installed the GM aluminum heat shield that goes under the carb base and used two thick base gaskets for extra insulation. These engines run the 4346 780 Holley carb but the same rules apply to other carbs. I ran #73 jets on the primary side which are one size richer than what came in 1966. I toyed a lot with the advance curve with different weights and springs until things worked right. No numbers for that part of the mods. I drove the car that way from 1998 until 2012 with no problems.

 

[2KforeverC5]

Before we bought our 2005 Corvette in 2012, I had a 1969 SS396 Chevelle with the L78 engine and 11-1 compression. First, I blocked the heat riser open. Getting heat away from the incoming air charge was the big thing. I added the sheet metal heat shield that snaps in between the heads. I blocked off the intake heat crossover passage in the intake. I also installed the GM aluminum heat shield that goes under the carb base and used two thick base gaskets for extra insulation. These engines run the 4346 780 Holley carb but the same rules apply to other carbs. I ran #73 jets on the primary side which are one size richer than what came in 1966. I toyed a lot with the advance curve with different weights and springs until things worked right. No numbers for that part of the mods. I drove the car that way from 1998 until 2012 with no problems.

That all make sense, sometimes simple minor comonsence goes a long way. Plus it works too. DIY methods are best sometimes. Thanks for the info. I don’t think any GOOD Mechanic would have thought of it. Cheers

 

[2KforeverC5]

Hello Roger. Have you tried Petro Canada's 94 octane to see if that makes any difference. Not sure if they offer it in Quebec, usually in the larger markets. You would still have the ethanol but curious to see if a higher octane might help. Take care and good luck.

Petro Can has a different detergent called TACTROL im not sure if it has something to do with ETHANOL!!!

 

[Rruuff Day]

All PC gasoline has ethanol. Tactrol is just a detergent trade marked by PC. All gasoline companies have there own version of cleaning detergents. It has nothing to do with ethanol.

 

[2KforeverC5]

All PC gasoline has ethanol. Tactrol is just a detergent trade marked by PC. All gasoline companies have there own version of cleaning detergents. It has nothing to do with ethanol.

Thanks. Now I’m really confused. If it’s Federal and Provincial regulations stations should not even put the percentage of ethanol on their pumps. Or should they???

 

[2KforeverC5]

Just bought the car about two months ago and I’ve been filling up with mostly Ultramar 91 octane, which as I understand contains ethanol.

This week is storage time, I'll be storing the car where it can also be looked at mechanically throughout the winter months. The car is in great shape, the only known issue (up until a couple of days ago) is that the steering needs attention. It gives me a hard time when trying to turn while at a dead stop and this will be addressed while in storage.

Anyway ....

Since I bought the car, I have been experiencing some “dieseling” (engine continues to run, cough and sputter when turned off) on a few occasions. This has happened a total of maybe five times in the relatively short time I've driven the car and this lasts about 5 seconds each time. After doing a bit of research, I decided to start using Shell 91 V-Power two days ago. So I pull into my local Shell and top-off a good half-tank worth of Shell 91 V-power. So now the gas tank is completely full (half Ultramar 91 and half Shell 91).

Took the car for a long drive and after turning the car off the engine keeps going, this time the dieseling is more intense, white smoke, some backfiring. This lasts a good 15 seconds (maybe more). So while this is going on, I turn the ignition on again. The engines resumes but at higher RPM. Can’t get the RPMs to come down. Stopped the engine in ‘drive' gear .... more dieseling.

After letting the car sit for a good 45 minutes, I re-start the car. Normal RPM by the sound of it. The tach is not hooked up because the previous owner had changed (upgraded) the ignition system and the stock tach cannot be hooked-up to the new distributor. This will be addressed during winter storage because it will require the removal of the dash.

My question is are the two issues related (the "dieseling" and the high RPM)?
Is (was) the use of the Ultramar gas the problem? Now that I've changed over to Shell VP 91 will the problem go away next spring?
Or, given the engine is of a higher compression, will this dieseling issue continue no matter what fuel I use (ethanol-free or not) and would octane booster be required going forward?

Could the problem be the ignition system itself? My neighbour tells me it may be too advanced (he drives a '68 Mustang). My mechanic tells me he checked the ignition and made sure it's where it's supposed to be, but he'll consider it again during the winter months while the car is in his care.

Thanks.

Start with steering - replenish power steering fluid. You might have to do it a few times but it’s worth a try.

 

[2KforeverC5]

All PC gasoline has ethanol. Tactrol is just a detergent trade marked by PC. All gasoline companies have there own version of cleaning detergents. It has nothing to do with ethanol.

Good to know I’ll stay with Shell seems like performance is there when I need it.

 

[Roger Ramjet]

Thought I would give an update ....

Adjusted the timing and now using Petro-Canada 94 for the past 5-6 fill-ups.

Car runs great!

 

[2KforeverC5]

Thought I would give an update ....

Adjusted the timing and now using Petro-Canada 94 for the past 5-6 fill-ups.

Car runs great!

Yes. Previously someone posted that Petro-Canada contains Ethanol as per Government regulation. I use to put the same in my tank now I’m back to Shell 91 and will stay as Shell user. Cheers