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02-25-2008, 01:40 PM
Why does carbon build up on the left side of my piston tops and not on the power side?

And, why is the sky blue?

Mickey Richaud
02-25-2008, 01:50 PM
Why does carbon build up on the left side of my piston tops and not on the power side?

And, why is the sky blue?

Because.

For a more enlightened answer, see here:

Andrew Mace
02-25-2008, 01:57 PM
Mickey, once again you've nailed it! (One of my all-time favorite comedy albums.)

TR6oldtimer
02-25-2008, 02:19 PM
Why does carbon build up on the left side of my piston tops and not on the power side?

And, why is the sky blue?
Not on the power side? You mean the bottom. Well....
The blue color of the sky is due to Rayleigh scattering.

poolboy
02-25-2008, 02:19 PM
Bill have you been running too rich? Have you ever noticed a gasoline smell in the oil on your dip stick?

02-25-2008, 06:10 PM
Nope, not running rich.

If you all were to remove the heads to your engines, you would all see carbon buildup on top of the pistons. The Bentley manual even has instructions on how to remove that carbon.

I guess that the power side (carb side) is hotter, that is why you stagger your rings away from that side.

TR6oldtimer
02-25-2008, 06:38 PM
So, you are saying the carbon builds up more on the spark plug side. This would suggest to me there is incomplete combustion upon the spark, but the gas mixture burns more throughly as the flame spreads across the piston.

A guess...

poolboy
02-25-2008, 06:41 PM
Yeah, and I believe it's recommended that one shouldn't get too enthusiastic about removing carbon build-up around the perimeter of the piston, especially in an older engine.

DrEntropy
02-25-2008, 06:44 PM
If it ain't comin' apart, let sleeping dogs lie. One chunk of "coke" down betwixt wall and piston is askin' fer trouble. Stuff the bores with paper towels instead!

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.

poolboy
02-25-2008, 06:55 PM
Wait until the 'skeeters are out!

TR6oldtimer
02-25-2008, 07:09 PM
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....

poolboy
02-25-2008, 07:14 PM
Ray, those were the Guys that could keep their tractors running 50 years.

BOXoROCKS
02-25-2008, 07:16 PM
...cause the extended sparkplug tip is doing its job....of bangin it off.

02-25-2008, 07:16 PM
Aren't these supposed to be <span style="font-style: italic">tractor motors</span>?

BOXoROCKS
02-25-2008, 07:19 PM
....hey Ray,..ever hear of the busted up walnut pieces to decoke a head? pour em in the carb while keeping the revs up....

poolboy
02-25-2008, 07:21 PM
The thing looks just like the engine in the car I learned to drive in. Mother's 52 Chevy. Well, maybe the carb was different.

TR6oldtimer
02-25-2008, 07:32 PM
<div class="ubbcode-block"><div class="ubbcode-header">Quote:] ....hey Ray,..ever hear of the busted up walnut pieces to decoke a head? pour em in the carb while keeping the revs up....[/QUOTE]
That's what Twosheds squirrels were trying to do, only from the wrong end....

https://www.britishcarforum.com/bcforum/ubbthreads.php/ubb/download/Number/9979/filename/Smoke.jpg

TR674
02-25-2008, 07:50 PM
Bill
I have the head off my engine at the moment and there are lots of loose flakes of carbon on the pistons. I'm curious as to why this doesn't get blown out with the exhaust gas?????? There must be a fair bit of air movement in there.
Regards
Craig

02-25-2008, 08:53 PM
Most mechanics I talk to (ok, they aren't LBC mechanics) say that is pretty much normal, caked carbon on the tops of the piston. Again, refer to the Bentley manual where they talk about removal of such. I don't believe that they would devote a section to this phenomenon knowing the economy of words they are noted for.

2wrench
02-26-2008, 10:25 AM
Everybody knows why the sky is blue.

The sky is blue for swatting shuttlecocks;
doing skeetshooting and watching air shows...

and, yes, Mickey,

Air is for blowing up volleyballs and basketballs.

Bill Cosby. The King of clean comedy.

vettedog72
02-26-2008, 05:15 PM
I understnad they should have a carbon film over the tops; it keeps the heat in the chamber and reduces the piston heat.

poolboy
02-26-2008, 05:37 PM
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
02-26-2008, 06:22 PM
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 &amp; 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
02-26-2008, 06:41 PM
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.

02-26-2008, 07:35 PM
https://i2.photobucket.com/albums/y17/billkaram/carbon001.jpg


Hmmmmmm.....

TR3driver
02-26-2008, 07:45 PM
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 &amp; 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.

02-26-2008, 10:36 PM
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
02-27-2008, 09:38 AM
Bill,

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

02-27-2008, 11:01 AM
Paul, notice how there is no carbon on the power side of your piston top.

RonMacPherson
02-27-2008, 12:13 PM
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
02-27-2008, 12:56 PM
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.....