Curious....

[vettedog72]

I understnad they should have a carbon film over the tops; it keeps the heat in the chamber and reduces the piston heat.

 

[poolboy]

The only real drawback to carbon build-up, as I understand it, is that it may lead to run-on due to the carbon holding enough heat to ignite gasoline vapors that may remain in the cylinder even after the plugs stop firing..dieseling?
And, a few thousandths of carbon may actually raise the compression ratio, by reducing the air space.

 

[TR3driver]

And, a few thousandths of carbon may actually raise the compression ratio, by reducing the air space.

Which is the other problem, it raises compression and hence increases octane requirements. The coating is typically not just carbon, but other solid gunk from the fuel & it's additives as well; and can be a lot thicker than just a few thousandths. Back in the days of leaded fuel, it was mostly lead oxide that would flake off when it got thick enough (leading to problems with glowing broken edges), but unleaded leaves a much harder deposit. If your engine runs cleanly enough (all the time), the deposit may not even be black.

 

[AweMan]

If you just HAVE to do something about it, wait 'til it's running again and mist some water into the throats at 3K RPM.

My old man use to spray a mixture of water and diesel oil into the carbs while the engine was running. He claimed it took care of carbon build up. The cloud of smoke was a sight to see. If I were to do that today, I'd be arrested.

He also would run a mixture of motor oil and diesel in the crankcase every third oil change to clean out sludge.

None of this appeared to harm the engines, but I'm not sure I would do any of this, however he learned about engines as a farm boy, and swore by these procedures.

I miss him....

My dad was a Mechanic for a large construction company for many years. He kept all kinds of equipment running and in good working order. He taught me many many things about engines and the like during his life. I have seen him, on more than one occasion do just exactly what TR6oldtimer mentioned. One thing to keep in mind if you do try the water mist down the intake is not to kill the engine while doing this. And don`t administer the water mist too fast as it can crack or warp a valve.
Diesel in the oil is also another thing I have seen him do. three quarts #1 diesel two quarts of detergent oil, DO NOT drive the car with this mixture. Idle only! I have seen the inside of an engine he rebuilt, immediately after these treatments were used to clean it up. You wouldn`t believe how clean it was unless you saw it with your own eyes.

 

[Guest]

Hmmmmmm.....

 

[TR3driver]

Just curious, Bill, have you checked the piston/head clearance ? That pattern looks a bit like a TR3 motor I had, where the pistons would kiss the head with a thin head gasket & high rpm. Using a standard gasket kept them from touching, but still left a pattern in the deposits. Never did figure out for sure what the problem was, but that's the same engine where the liner seats were apparently not parallel to the top of the block, so I'm guessing it was a poorly machined block from the factory.

 

[Guest]

Just curious, Bill, have you checked the piston/head clearance ?

I had the same carbon buildup in the same pattern on my pistons even before I had the head shaved. Go figure. I repeat, the repair manual makes a special issue of how to clean this stuff off so I assume that this is a common occurrence.

 

[Brosky]

Bill,

This was what mined looked like after 54,000 miles. I don't know how many miles are on yours?

 

[Guest]

Paul, notice how there is no carbon on the power side of your piston top.

 

[RonMacPherson]

Years ago, Hot Rod magazine had a writer names MCFarlane working for them. He wrote extensively on engines, especially compression, combustion, carbon buildup, breathing. Those articles were very informative. Over the years I have those articles to have been very accurate. Found out he was an engineer and after he quit writing for Petersen Publications he went to work for Edelbrock.

If you ever get the chance to go through the old Hot Rods, please do so. Look for articles by James McFarlane or maybe MacFarland, it's been so long I'm not sure on the recall of the spelling, but definitley articles worth researching.

 

[Brosky]

Well, now that you mention it, this looks pretty similar to the many engines that I've had apart over the years. Forget the aluminum Caddy's with the leaking intakes, I don't think that this is an abnormality in that the exhaust exits there. And the swirling that will take place inside the cylinder chamber after combustion takes place and the hot gases exit the valves may cause this to occur.

JMHO.....