Fuel for '70 LT-1

[Bob R.]

[Tim S.]

Re: Fuel for '70 LT-1

Where the heck do you find 100 LL avgas for $4.30/gallon?

It's $4.00 gal by me

[Duke W.]

Re: Fuel for '70 LT-1

I'm surprised at the difference in avgas prices across the country. In CA 87 PON regular unleaded is at or pretty near four bucks a gallon. Mogas prices vary because of different formulations and state taxes. Avgas is the same formulation nationwide, and I don't think it has state taxes... just federal.

Duke

[Mark E.]

Re: Fuel for '70 LT-1

Doesn't leaded gas contribute to deposits on valves and plugs?

Plus exhaust systems last virtually forever with unleaded.

[Mark F.]

Re: Fuel for '70 LT-1

Doesn't leaded gas contribute to deposits on valves and plugs?....

Yes, and the culprit is Lead Bromide (PbBr2) according to this website on "Lead Fouling"

https://www.shell.com/business-customers/aviation/aeroshell/knowledge-centre/technical-talk/techart-18-30071600.html

[Keith W.]

Re: Fuel for '70 LT-1

NW Georgia. It was mid $2/gal before the November election.

[Martin T.]

Re: Fuel for '70 LT-1

I have a 1970 LT1 Z28. In California, it seems to not do as well on pump 91 without mixing in about a third of 110. The diesel that occurs on pump gas stops and the car runs much stronger.

[Duke W.]

Re: Fuel for '70 LT-1

Yes, and the culprit is Lead Bromide (PbBr2) according to this website on "Lead Fouling"
https://www.shell.com/business-custo...-30071600.html

I question this statement from the above article.

To achieve this a lot of TEL is used - around 5 times the quantity that was used in the old Leaded automotive fuels.

100LL avgas is called such because it has low lead. I believe the current limit is 0.5 grams of Pb per gallon. That's the actual weight of the lead in the TEL, which is usually specified as cc per gallon. Off the top of my head I can't remember the conversion factor.

In any event traditional leaded mogas typically had from one or two to maybe up to five cc of TEL per gallon, and avgas had more. Lead oxide is a white solid that can coat combustion chamber boundaries and build up in exhaust system. The bromides are called scavengers because they react with the lead to from lead bromides that condense at lower temperatures and are purged from the cylinders and most of the exhaust system as gas. This slows the buildup of white lead oxide in the combustion chamber.

We used to say that white exhaust pipes meant the engine was running lean. When the mixture is near stoichiometric there is little free carbon, so it's the white lead oxide that builds up inside the exhaust system.

Duke

[Mark F.]

Re: Fuel for '70 LT-1

I question this statement from the above article. To achieve this a lot of TEL is used - around 5 times the quantity that was used in the old Leaded automotive fuels....

colouredcentre
Thanks for your input - Happy EASTER!

https://www.epa.gov/sites/production/files/2015-03/documents/compendium-0506.pdf

[Joe L.]

Re: Fuel for '70 LT-1

colouredcentre
Thanks for your input - Happy EASTER!

https://www.epa.gov/sites/production...ndium-0506.pdf

Mark------


Aviation gasoline is on the cusp of being de-leaded. Actually, the EPA-mandated deadline for elimination of lead in aviation gasoline is long-since passed. The lead continues only because no viable alternative was available for a very long time. There are non-leaded formulations now that are on the brink of FAA-approval. When that occurs I expect leaded formulations to quickly disappear.

The scavengers used in leaded gasoline are deleterious to everything in the fuel system, especially carburetors. The damage they cause cannot be "rebuilt out of" carburetor cores. It's the reason that many rebuilt carburetors don't perform like new carburetors.

As I've mentioned before, the late Chevrolet performance expert John Lingenfelter once said "the best thing that ever happened for performance is unleaded gasoline".

[Mark F.]

Re: Fuel for '70 LT-1

Mark------ Aviation gasoline is on the cusp of being de-leaded. Actually, the EPA-mandated deadline for elimination of lead in aviation gasoline is long-since passed. The lead continues only because no viable alternative was available for a very long time. There are non-leaded formulations now that are on the brink of FAA-approval. When that occurs I expect leaded formulations to quickly disappear. The scavengers used in leaded gasoline are deleterious to everything in the fuel system, especially carburetors. The damage they cause cannot be "rebuilt out of" carburetor cores. It's the reason that many rebuilt carburetors don't perform like new carburetors. As I've mentioned before, the late Chevrolet performance expert John Lingenfelter once said "the best thing that ever happened for performance is unleaded gasoline".

Hi Joe,

Thanks for the update and info.
And yes, I should have mentioned that EPA link goes all the way back to May 2006...

I did not know about the scavenger/carburetor problem, but it doesn't surprise me because many halogenated compounds are moderately to very reactive (not sure where EDB or EDC fall relative to others).

Also, along with the lead bromide and lead chloride formed during combustion, I'll bet there a detectable amounts of hydrobromic and hydrochloric acids created as well - both of which are nasty actors, too.

[Duke W.]

Re: Fuel for '70 LT-1

I have a 1970 LT1 Z28. In California, it seems to not do as well on pump 91 without mixing in about a third of 110. The diesel that occurs on pump gas stops and the car runs much stronger.

i
Assuming the engine still has the emission control oriented spark advance map you can probably at least mitigate and perhaps even eliminate the run-on by converting the ported vacuum advance to full time with a B28 VAC, and install lighter centrifugal springs to get the centrifugal in as fast as possible. The closer you can get to the 327 365/375 HP spark advance map the better.

Read my tuning seminar and pay particular attention to the chart on emission controlled engines.

http://www.metroli.org/pdf/2012%20Nationals%20tuningseminar.pdf

Duke

[Mark E.]

Re: Fuel for '70 LT-1

i
Assuming the engine still has the emission control oriented spark advance map you can probably at least mitigate and perhaps even eliminate the run-on by converting the ported vacuum advance to full time with a B28 VAC, and install lighter centrifugal springs to get the centrifugal in as fast as possible. The closer you can get to the 327 365/375 HP spark advance map the better.

Read my tuning seminar and pay particular attention to the chart on emission controlled engines.

http://www.metroli.org/pdf/2012%20Nationals%20tuningseminar.pdf

Duke

What I'm getting from this thread-

Leaded gas:
- Causes build up on valves, spark plugs and exhaust systems
- Deteriorates carburetors
- Is a dangerous pollutant

And as Duke says, our engines run great on premium unleaded with the right ignition advance,. This made all the difference with my LS5.

[Larry M.]

Re: Fuel for '70 LT-1

Tetraethyl lead was never sold or added directly to gasoline. It was blended at the chemical production facility and made into either TEF (Tetraethyl lead fluid) or MAF (Mixed alkyl lead fluid). The latter contained a mix of tetraethyl lead (TEL) and tetramethyl lead (TML) and all of their various intermediates. It used a BF3 catalyst and reacted the TEL and TML to make the mixed alkyls. Certain refineries preferred the MAF material over the TEF material in their leaded gasolines.

The TEF or MAF fluid for automotive gasoline contained the lead plus about 20%(wt) Ethylene dibromide and 20% (wt) Ethylene dichloride as lead scavengers plus 2% inerts and red identifying dye.

The engine combustion products most certainly produced hydrochloric acid and hydrobromic acid in the exhaust system...........and was the reason that our carbon steel exhaust systems (tailpipes and mufflers primarily) corroded out after only 2-4 years of driving. The combustion of gasoline produces both CO, CO2, and water as byproducts......which combined with the lead scavenger combustion products, produced the dilute acids.

I was a chem engineer working for one of the three companies that produced organic lead for gasoline industry back in the day. So I am very familiar with both how it was manufactured as well as how it was used and blended in gasoline. I personally made it, blended it, and handled/mitigated many of its environmental issues.

I also agree that it was a good thing to get it out of our gasoline. But it certainly can increase octane in gasoline for use in certain selected cars and trucks.

Larry

[Lawrence S.]

Re: Fuel for '70 LT-1

i
Assuming the engine still has the emission control oriented spark advance map you can probably at least mitigate and perhaps even eliminate the run-on by converting the ported vacuum advance to full time with a B28 VAC, and install lighter centrifugal springs to get the centrifugal in as fast as possible. The closer you can get to the 327 365/375 HP spark advance map the better.

Read my tuning seminar and pay particular attention to the chart on emission controlled engines.

http://www.metroli.org/pdf/2012%20Nationals%20tuningseminar.pdf

Duke

I can tell you that I have used Duke's tuning methods on my 67 L79, 69 Z28, 69 L71 with great results in all three cars. I generally use 91 non ethanol fuel here in Charlotte with good results. On occasion I will use 93 ethanol with no detonation but the cars don't run as well as they do with the 91 non ethanol. I only run the 93 ethanol when I have to and usually only put in 5 gallons.
I have used 110 leaded race gas and the cars clearly run well, but at the price for the fuel I can't make sense of using it. There is not that big of a difference in performance as far as I can tell.