White Exhaust Valves

[Frank Howard]

Blew the head gasket a couple of weeks ago. I could see coolant peeing from the rear edge of the gasket. When I removed the head, all four exhaust valves were coated with a white crusty substance. The intake valves had an expected amount of carbon build-up. I cleaned them up last night but I thought I'd post some before/after pictures.

[Andy8421]

I had the same question. Googling brings up lots of threads on this issue from all sorts of cars. Consensus seems to be that the white deposits are ash from burning oil that get deposited on the exhaust valves because of their extremely high temperature - which seems plausible I guess.

I use Miller's octane booster / lead replacement additive which seems to leave brown deposits on exhaust valves and sparking plugs. I have assumed this is due to a similar process.

[denicholls2]

My first thought on looking at the pictures was that you've managed to find leaded gasoline. That is definitely the explanation for "octane booster".

All engines used to look like this. You could easily tell the state of tune of the engine by the tailpipe color, which was the same as the valves but a whole lot easier to see :

- Black = Too Rich
- White = Too Lean
- Brown = Just Right.

Since unleaded gasoline, the biggest variation is typically dark gray to black.

Your engine is running lean, methinks. With Webers, could be that the idle circuit is fine and the mains are overlean. This would in turn cause stumbling or gurgling, or "lean stumble" at steady (no accelerator pump in play) highway speeds.

If most of the engine run time is around town, the idle circuit is more likely lean.

[Frank Howard]

Thanks for your responses guys. Perhaps I should have included a bit more detail in my original post. As you can see, this is a Stromberg head. Since I went through the motor in 2002, the car has always run just fine. Starts right up, idles smoothly, plenty of smooth power delivery, no stumbling or missing at all, 29mpg around town, 38mpg highway. Hard to believe, isn't it?

As noted above, the head gasket was installed in 2002. The only reason I took it apart was because for some unknown reason, the head gasket blew. One more thing. I use the car on a daily basis (7 months out of the year) and it runs on mid-grade (89 octane) unleaded gasoline. No pinging or pre-ignition at all. As I said, it really runs great. Just don't know where the white crusty stuff came from.

So far, I like the lean running theory the best. I know there is a slight mixture adjustment for Strombergs as I have the special tool with Allen wrench. Perhaps I'll try to richen the mixture when I get it back together. Really hate to mess with it as it runs so good now.

[david.g.chapman]

Hi Frank,

I too have a Stromberg head, and mine is low compression. I have been having trouble with exhaust valves burning out, and they were a light brown colour when the head was inspected. As I have good NOS valve springs, I have put it down to running too lean, especially as others on the forum have suggested as much.

So I have:

1. Made the mixture richer (so the spark plugs show a light greyish brown colour). If the air filter is at all blocked it seems to affect the idling mixture, making the plugs darker and fooling you into adjusting for a leaner mixture. So I would check the filter is new or nearly so. When I replaced my dirty filter I found I could raise the needles a lot (10 thou) and still have clean plugs.

2. Switched to 97 RON super unleaded fuel. I understand that unleaded fuel burns hotter then the old 5 star, and the Stromberg head seems to run hot anyway. Switching to super might help if you don't want to go down the lead replacement route.

So far so good - compressions still OK....

Dave Chapman.