Unleaded Gas
 

When leaded gas was banned cars at the time began to suffer valve/seat erosion. The fix for the classics at the time was rebuilding engines with stainless valves and hardened seats. Seems the problem of unleaded gas is no longer a problem with older vehicles - just wondering why. Is there now additives in gas that provides the lubrication that lead use to ? Can older engines up to the early 70s now be rebuilt with stock valves and seats ? Inquiring minds want to know.

Re: Unleaded Gas
 

I put Marvel Mystery Oil in Gas only,helps with lubrication upper end,valves etc. Never a problem.

Re: Unleaded Gas
 

lead was added to fuel as a anti knock agent for hi compression. Before that is was unleaded.

Re: Unleaded Gas
 

Lots of good info here.
https://en.wikipedia.org/wiki/Tetraethyllead
Am not sure, but have been told the A runs fine on unleaded and does not require Lead Substitute.
As far as other cars from the late 30s/40s/50s/60s maybe use of lead substitute on vehicles not upgraded require lead substitute?

Re: Unleaded Gas
 

Good afternoon all...As I understand it, our 'A's are low compression if stock. Like 4.2 and even with higher compression heads...not usually over 6.0. No lead substitute required. The cars of the late 50's and 60's had V-8 engines and much higher compression...they were designed to run on leaded gasoline. I had my first 'A' in the early 60's and ran the most inexpensive gas that the shell station where I worked had. The car ran fine...Today I have a 31 Tudor with a 5.5 head and run regular gasoline...and the old girl is happy. I don't believe that leaded gas was available in 1931. Ernie in Arizona

Re: Unleaded Gas
 

I occasionally drive leaded petrol (AVGAS) in my 4 classic cars. With all of them I can confirm that the motors run noticeably softer.

Re: Unleaded Gas
 

I use a product that I don't think is available in the US. It is made by a friend and sold almost everywhere else in the world. It is called Flashlube. It prevents valve seat recession and acts as an upper cylinder lubricant. 1 ml in a litre of fuel is all it takes. That's a ratio of 1:1,000.I always have at least one 50ml bottle in the door pocket.

Re: Unleaded Gas
 

Today the anti-knock additive is alcohol - which by a surplus of oxygen attached "oxygenates" the fuel/air mix and improves burning - thereby preventing knock.

MTBE was used for a while between tetraethyl lead and alcohol, but that was found carcinogenic and was "embedding itself" into the fuel chain.

Wikipedia: Tetraethyl Lead

As others have said, the fuel of the Model A era was lucky to be in the high 60s octane rating, which kind of presented a natural limit to compression ratios (and lesser to engine construction mitigations.) Today most "regular" gas has an octane rating of 87 and "high test" might be up into the mid 90s. Some av-gas is over 100.

All you need to know about Octane is found at https://www.eesi.org/papers/view/fac...tory-of-octane

Joe K

Re: Unleaded Gas
 

As I understand it the lower octane fuels actually are easier to ignite and burn and will provide more power than the high octane fuels.
The octane number is a measurement of resistance to pre-ignition. The higher the octane number the harder it is to ignite the fuel making it a better choice to run in a high compression engine but gives no benefit to a lower compression engine such as what we have in our Model A's.

Re: Unleaded Gas
 

You are absolutely right. In fact, there are more BTU's of energy per gallon in regular gas than premium high octane gas. On the other hand, high compression results in greater efficiency (more power from the same amount of fuel) so it's somewhat of a trade-off, with high compression coming out on top.

Re: Unleaded Gas
 

I would have never thought that possible and would have argued (like an idiot). Thanks to you two for bringing that to our attention.

Re: Unleaded Gas
 

The relationship of gasoline and valve train performance is not correct in my opinion. Look through the Ford service bulletins and you will see that valves were problematic in the Model "A" engine before leaded gasoline. The metallurgy was not corrected during Model "A" production, and not before WW2. WW2 high performance fighter plane engines and post war racing brought about major improvements in valve technology.

Re: Unleaded Gas
 

In the model A era you had low compression, long stroke, slow turning engines so low octane fuel was fine. Then in the 50s and 60s engines started having higher compression, shorter strokes, higher RPM and needed higher valve spring pressure. Lead was added to boost octane for the higher compression engines and the lead acted as a cushion on the valve seat. Then they outlawed lead in the gas so engine builders had to go to hardened valve seats. For our Model As I think you could get away with regular valve seats because our engines are slow turning with weak valve springs. But hardened seats are so common now that there is no point in not using them.

Re: Unleaded Gas
 

Correct -although hardened valve inserts do expand and contract at a different rate to the block with changes in heat. This at least theoretically sets up a whole lot of stress in the valve seat area -Significant ? who knows ?

Lead was a Chev innovation (much later than the Model A ) Henry wasn't ever going to recommend its use !

Re: Unleaded Gas
 

I use Moreys Upper cylinder lubricant I think a lot of guys on here use MMO.
I'm really not sure that any of it does what it claims to do. Sometimes I convince myself that the car runs better with additives other times I think its all snake oil -Would love to see some really well designed trials -In the meantime i remain a semi committed user !

Re: Unleaded Gas
 

I have a plumber friend who was running his Hiace van on LPG. It didn't take long for the valves to recede into the head and burn out. He repaired it and started using Flashlube and hasn't has any trouble since. He installed a dispenser on the firewall that drips the lube into the manifold at about 6 drops a minute. I've never had a sticky valve or any other valve problems with any of my As and I've driven lots of miles with no inserted seats. I see no point to removing good, solid cast iron to put them in. These engines are prone to cracking at the valve seats anyway. (especially on #2 and 3 cylinders)

Re: Unleaded Gas
 

And back in the 20's and 30's Octane was in the 60's!

Re: Unleaded Gas
 

Look here for the history leaded gasoline.
http://www.columbia.edu/itc/sipa/env...agu1990%29.pdf

Re: Unleaded Gas
 

When the Model A was built the only fuel was "White Gas" There was no lead added nor needed. No lead fuel will cause no issues with our cars. Now Alcohol in our fuel does cause problems especially when most our cars sit more than are driven and the fuel separates and makes a mess of our fuel lines, tank, carb etc.

I use alcohol free fuel which I can get locally. Now touring it is not as important if I am running the fuel through and then fill up with the good stuff when tour is done.

Re: Unleaded Gas
 

I use MMO in oil and gas.I saw a friend drain oil into a metal drain pan.The oil stuck to the sides of the pan when he poured it out,had to wipe it off the sides of the drain pan. I have used it ever since.