Leaded fuel question...

[John D.]

Re: Leaded fuel question...

My father used to preach to me that if I wanted to have a good running, long lasting, clean engine to only use Amoco white gas as he called it in old days. You old timers know that as Amoco's hi test. On all the fuel cars, etc we drove for many a years we ran that and 260 Sunoco.
Only blew two engines.

[Michael W.]

Re: Leaded fuel question...

I've never seen or heard of a Corvette that suffered damage on the exhaust valves seats through use of unleaded gas. Has anybody?

Anybody got a guess in which millenia this myth will finally be put to rest?

[Clem Z.]

Re: Leaded fuel question...

My father used to preach to me that if I wanted to have a good running, long lasting, clean engine to only use Amoco white gas as he called it in old days. You old timers know that as Amoco's hi test. On all the fuel cars, etc we drove for many a years we ran that and 260 Sunoco.
Only blew two engines.

amoco white gas had some other additive instead of lead. my dad always bought it for use in his blow torch

[Clem Z.]

Re: Leaded fuel question...

I've never seen or heard of a Corvette that suffered damage on the exhaust valves seats through use of unleaded gas. Has anybody?

Anybody got a guess in which millenia this myth will finally be put to rest?

there must be a reason or GM would have not gone to the expense of induction hardening of the exhaust valve seats in cast iron heads when they switched to unleaded fuel

[Mike G.]

Re: Leaded fuel question...

when everything was rebuilt they probably used modern day parts like valve seats. no lead additive is needed. i like to use it on old fuel injected engines but probably dont really need it there either. my cars run fine on 93 pump gas. i use amoco 93 in everything i have, even the lawnmower.

[Joe L.]

Re: Leaded fuel question...

amoco white gas had some other additive instead of lead. my dad always bought it for use in his blow torch

clem------


Yes, Amoco "white gas" was the first unleaded fuel and was available WAY before any other unleaded fuel was available. It was around when I was a child and unleaded gas didn't become otherwise widely available until about 1971.

[Bill I.]

Re: Leaded fuel question...

I know we're getting side tracked a bit here. Some Sunoco stations would remove that silver button stop on the pump and pump Sunoco 280, the little wheel showing the reg fuel being pumped never moved. Bill.

[Joe L.]

Re: Leaded fuel question...

there must be a reason or GM would have not gone to the expense of induction hardening of the exhaust valve seats in cast iron heads when they switched to unleaded fuel

clem------


I've often thought about that, too. GM doesn't do things like this without a good reason. However, I attribute it to the fact that GM can't control situations in which folks might use the engines at high power levels for extended periods (e.g. towing trailers up long grades, etc.) AND they wanted to be "over-cautious" as they went into the era of unleaded gas. I think the induction hardening was a relatively cheap way to help prevent a rash of warranty claims from folks who did use their engines for high power levels for extended periods.

As I mentioned, though, I've had the opportunity to talk to quite a few fleet managers who had in fleets under their purview older industrial engines without hardened valve seats that ended up running on unleaded gas. These engines were run at high power levels for extended periods (for things like generators, pumps, etc.). All of them told me that they never had a problem with these engines after the switch to unleaded gas.

Notwithstanding the above, if I had an engine that I was using for high power levels for extended periods (like regularly pulling a heavy trailer over the Sierras or the Rockies), I'd want an engine with hardened valve seats. For the kind of service that just about any classic Corvette receives, I think hardened valve seats or lead additives are totally unnecessary.

If one is rebuilding an engine and doesn't mind the extra cost, installing hardened exhaust valve seats might not be a bad idea. Not necessary, but not a bad idea. However, there is a down-side to it, especially for 2.02/1.60 small block heads. Installing hardened exhaust seats in these can cause one to "strike water" and ruin an otherwise valuable cylinder head. Plus, regardless of the engine and valve size, if one of the seats should come loose, the whole engine could wind up scrap.

As far as using lead additives, I'd never do it. As far as using non-lead, lead-substitute additives, especially those concentrated ones like Alemite CD2 (which contain Powershield as the active ingredient and require only a few ounces per tankful), those are fine if one is prone to worry.

[Clem Z.]

Re: Leaded fuel question...

clem------


I've often thought about that, too. GM doesn't do things like this without a good reason. However, I attribute it to the fact that GM can't control situations in which folks might use the engines at high power levels for extended periods (e.g. towing trailers up long grades, etc.) AND they wanted to be "over-cautious" as they went into the era of unleaded gas. I think the induction hardening was a relatively cheap way to help prevent a rash of warranty claims from folks who did use their engines for high power levels for extended periods.

As I mentioned, though, I've had the opportunity to talk to quite a few fleet managers who had in fleets under their purview older industrial engines without hardened valve seats that ended up running on unleaded gas. These engines were run at high power levels for extended periods (for things like generators, pumps, etc.). All of them told me that they never had a problem with these engines after the switch to unleaded gas.

Notwithstanding the above, if I had an engine that I was using for high power levels for extended periods (like regularly pulling a heavy trailer over the Sierras or the Rockies), I'd want an engine with hardened valve seats. For the kind of service that just about any classic Corvette receives, I think hardened valve seats or lead additives are totally unnecessary.

If one is rebuilding an engine and doesn't mind the extra cost, installing hardened exhaust valve seats might not be a bad idea. Not necessary, but not a bad idea. However, there is a down-side to it, especially for 2.02/1.60 small block heads. Installing hardened exhaust seats in these can cause one to "strike water" and ruin an otherwise valuable cylinder head. Plus, regardless of the engine and valve size, if one of the seats should come loose, the whole engine could wind up scrap.

As far as using lead additives, I'd never do it. As far as using non-lead, lead-substitute additives, especially those concentrated ones like Alemite CD2 (which contain Powershield as the active ingredient and require only a few ounces per tankful), those are fine if one is prone to worry.

like i posted above if the engine was run on leaded fuel the valves and seats had enought lead to last the life of the engine even running on unleaded fuel later. i wonder would would happen if these engines had a valve job and continued to be run hard on unleaded with no hardened seats. if you just drive up and down the road or off and on a trailer you are in no danger of hurting the heads

[Jack H.]

Re: Leaded fuel question...

Who remembers the Sinclair TV/Radio jingle from the 60's?

"Sinclair puts the nickle in..."

Apparently tetraethyl lead isn't the only octane boosting additive.

[Ridge K.]

Re: Leaded fuel question...

for real hi compression race engine you still need leaded fuel as unleaded race fuel is only up to 100 octane. it is also very light sensitive and must be stored carefully.

Clem, the unleaded fuel used by NASCAR now is Sunoco 260 GTX, rated at 104 octane.

[Duke W.]

Re: Leaded fuel question...

RON? MON? PON?

Duke

[Clem Z.]

Re: Leaded fuel question...

RON? MON? PON?

Duke

here you go duke. http://webcache.googleusercontent.co...&ct=clnk&gl=us for some reason they list it as off road use

[Clem Z.]

Re: Leaded fuel question...

looks like they have a lot of unleaded racing fuel. http://www.sunocoinc.com/Site/Consum...UnleadedFuels/

[Duke W.]

Re: Leaded fuel question...

here you go duke. http://webcache.googleusercontent.co...&ct=clnk&gl=us for some reason they list it as off road use

According to this spec sheet the "104 octane" number is RON. They also list the MON as 94, and the PON, which is (R + M)/2 is 98.

The difference between RON and PON is called "sensitivity" and is typically in the range of 8-10.

The posted octane number required on US road fuel pumps is PON, but Europe and most of the rest of the world still uses RON. So "98 octane" in Europe is equivalent to our 93-94 PON.

There is also the Aviation Method, which is used for aviation gasolines such as 100LL. The test is unique, but the numbers are usually very close to MON. So 100LL avgas is about 108 RON and 104 PON. That's why a small amount in pump premium - usually no more than 25% - will quell any detonation on a vintage road engine.

Whenever talking about "octane", unless the specific measurement context - RON, MON, PON, or aviation method is understood, any comparisons are meaningless.

As far as this fuel being listed as "off-road" it's probably because it has a low vapor pressure and probably doesn't meet most, if any, of the vapor pressure range standards that apply in various parts of the country at various times of the year.

The 10 and 50 percent boiling points are listed as 183F and 221F, respectively, which are very high. Typical road gasoline blends are usually in the range of 90-120F and 180-200F respectively, with winter blends at the low end and summer blends at the high end. So this blend has excellent vapor lock properties, but could cause hard starting on road engines.

This blend's aromatic content may also be above the legal limits for road fuel. Aromatics (ring type molecules such as benzine, C6H6) have high octane, but are carcingenic and their concentration in road fuels are limited by the EPA.

It's all in the details.

Duke