Pulled the head off today... opinions on that redish color on cylinders 5 and 6? Is that just the junk left from the additives in the gas?

Tops of pistons:


5 and 6 on the head

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70 Plymouth Valiant 4dr

Have you by chance been using an octane boost product? Many of these contain organic/metal complexes that leave reddish residues upon combustion.

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Methylcyclopentadienyl manganese tricarbonyl (MMT) - leaves magnesium oxide deposits

Ferrocene - leaves iron oxide deposits

Iron pentacarbonyl - leaves iron oxide deposits

They all are effective at raising octane level but are self defeating because they also eventually leave crust that promotes detonation, particularly the iron compounds.

Best octane boost available is either tetra ethyl lead or even better is iso-octane, otherwise known as 2,2,4-trimethyl pentane.

Brian

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Sorry, obviously MMT leaves manganese deposits not magnesium

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ahhh i see.... every 8,000 miles or so, i put water remover / octane booster in the gas tank.. many of the gas stations around where i live have water issues..

that explains the reddish color.. awesome.. thank you guys...

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70 Plymouth Valiant 4dr

Water remover is fine, but those octane boosters are leaving the residues.

b

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Forgot to mention, iso-octane is actually the standard for octane rating, it is 100 octane. Of all the isomers of octane, 2,2,4-trimethylpentane burns the most efficiently, because it isn't a long carbon chain, it's more of a spherical-shaped molecule and is thus very volatile and burns very evenly.

When discussing fuels having octane ratings above 100, usually oxygenated additives are used to get the fuel to burn even better, faster, more evenly, e.g. alcohols, ethers, nitrous oxide, and the like.

If you are going to use high octane fuels, stay away from additives with metals in them, better to use only organics, like alcohols, ethers, iso-octane.

Brian

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I've been finding the reddish-brownish deposits in engines for decades with no octane boost. Nothing unusual.... I just assumed it was in the fuel additives.

Now the orange color on that one valve is certainly different.

No telling what the various oil companies put in their gasoline. Many advertise "cleaning agents" and "detergents" and "corrosion inhibitors," can't say what these are and the regulators don't really put any responsibility on them to divulge what's in them.

brian

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