I pulled the head off today to change my camshaft and I"m somewhat taken aback at the colors I see in the engine.

The exhaust manifold is coated very faintly with a rust colored brown something, and the combustion chambers have colored faint deposits. The pistons do not have any brown on them.

Pics:




Any ideas what's with the rust color looking stuff? Even the plug insulators have it.

I didn't take pictures of the pistons, but they have no brown deposits, and they look rather.... well, like alumnium color.

BTW, the valves are Stainless... They have discolored, and look like they've been hot, even though I have run them extremely loose. The head's back on now, but not torqued yet, as it got dark outside.

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'81 W150 on Propane... Oversize valves, Oregon Camshaft cam, 10:5 static CR, Distributorless ignition, megajolt timing controller, PowerTrax lockers.

I don't see anything at all abnormal or worth worrying about in these photos. Combustion is never perfect, even with gaseous fuel like propane or natural gas. And don't forget there's always going to be a slight amount of oil in the combustion chamber, even with an engine in near-perfect condition. Bolt it back together and keep driving.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I expected the valves to retain the metalic silver look, and not discolor. That part worries me.

The reddish stuff spread all over just sort of baffles me, as I have no idea what it is. It "COULD" be the oily stuff that precipitates out of the propane coming from the converter.

I found a mechanism to lower the temperature of the converter, and the maker insists will prevent the "refracturing" of the propane and it will run cleaner and better.

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'81 W150 on Propane... Oversize valves, Oregon Camshaft cam, 10:5 static CR, Distributorless ignition, megajolt timing controller, PowerTrax lockers.

Different gases burns different colors

Worry if it makes your life better, but I don't see anything at all abnormal or worth worrying about in these photos. "Stainless" steel just doesn't rust. It does discolour when heated.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I have T304 pipes at my exhaust manifolds and they are now a straw colour.

From your photos, it appears that the combustion chamber deposits are not consistent across the engine. It looks to me that they may be ash deposits from oil consumption which varies from cylinder to cylinder.

It looks like there may be some scale in the cylinder head's water passages. This would be a good time to boil out the head.

Are you running it on pump gas or propane?

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I may be slow,but I"m ahead of you.

When it comes to stainless, think, "stains less", not "impervious to stains and corrosion". MORE

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

LOL, the head was just cleaned to infinite cleanliness about 2K miles ago

The appearance of scale is caused by the application of gasket sealer to the shim head gasket (something I'm not doing this time). It's a pain to remove.

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'81 W150 on Propane... Oversize valves, Oregon Camshaft cam, 10:5 static CR, Distributorless ignition, megajolt timing controller, PowerTrax lockers.

Would that mechanism be a Gann Thermostat (PN M-456)? As for converter temperature control, see:

• Temperature Control, propane sludge, long thread.
• increasing density by reducing coolant temperature

You stated in the header its on propane-if thats true then your running the mixture too rich,if its on gas then its a additive in the gas used to bring the octane up or lead subsitute

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I may be slow,but I"m ahead of you.

yes, I'm running it on propane. It was rich briefly, while I was experimenting with the carb, but most of the time it has run with a closed loop feedback controller in operation which seems to make it a bit too lean, not rich.

I broke my O2 sensor today so it's going to be a bit before it gets back to running with the closed loop controller. I really don't see how it could be rich, though. I cranked the load adjustment back to the point it was mostly gutless again

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'81 W150 on Propane... Oversize valves, Oregon Camshaft cam, 10:5 static CR, Distributorless ignition, megajolt timing controller, PowerTrax lockers.

These look similar:

https://altfuel.com/thermostats.htm

http://www.usgemini.com/Misc-Propane-Parts.html

I've been trying to find the parts to move the fill from the tank to the place where I removed the gas tank filler (not far apart) and am not having much luck. Just can't seem to find the fittings. Perhaps I don't have the right name or something. We fill it using the big round screw on connector that normally has a plastic cap (not plug) over the top, and contains a one way valve.

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'81 W150 on Propane... Oversize valves, Oregon Camshaft cam, 10:5 static CR, Distributorless ignition, megajolt timing controller, PowerTrax lockers.

To tune it on propane you need a gas analyser because propane burns so clean O2 sensor is useless and on the feedback dual fuel vehicle it has a false signal from a adapter. you tune it for low co reading just over zero.A second way is to tune it for a reduction in power of about 15 % less then maximum power.IMPCO has the most parts avaible and you need to regulate the temp of the water into the convertor.If it gets too hot the propane "cracks" when going from liquid to vapor and will turn the mixer and convertor into brown slime much like you have on the head. As far as locating the fill point I don't think I have ever see that done before because of the shut off at the tank filler.

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I may be slow,but I"m ahead of you.

Those are the Gann thermostats I thought you were referencing. One of the members of my propane forum tried one but didn't find that it worked as well as he had hoped it might.

As for adjusting the fuel mixture, O2 sensors do work. Impco's recommendation for using a gas analyzer might be because O2 sensors only became commonplace in automotive feedback systems in the early 1980s while Impco propane systems have been around since 1958. All of Impco's EPA and CARB certified systems require the use of O2 sensors for feedback control. As I explained earlier, feedback systems lean-out a rich mixture to stoichiometric. They can't make a lean mixture richer.

As for propane residuals, some of them originate from the impurities dissolved in the fuel, which will appear in the converter as large quantities of LPG are vaporized. Because commercial LPG does not have a specific constitution, some of the residuals originate from the polymerization of propylene. To combat this, HD-5 propane is specified for automotive use and the "5" refers to the 5% maximum limit of propylene.