Piston top spots with no carbon

[GPierce]

Removed my head to install a Snyder 6.1. No water leaks. In 7000 miles I have added no water, I check it before I drive the A.

When I removed the head I found these areas on the piston tops with no carbon. That to me is a sign of water leaking into the cylinder.

I could see no evidence coolant leaks on the head or block.

Several months ago I was on tour of the Smokies and following 3 other cars, all with high compression heads. Day one I no problem in the hills keeping up.
The next day I filled up with non-ethanol gas at a small mom and pop.
That day I was having a little trouble keeping up and it seemed the engine at times was not developing full power even though it was running smooth. I played with the GAV and the timing, no help.

Later I that day I was full throttle on a slight hill and all of sudden a I got burst of power.

When I got home I found my glass filter bowl full of rusty water. I pulled the Tillotson carb apart and found fine rusty debris in the float bowl all the way up to the top of the main jet.

I cleaned up everything and now have normal power. Flushed the gas tank and got more water and junk. It did not come from my tank. I had to have come in the gas I bought.

Question: Is there something that would leave that pistop tops clean other than water in the cylinder? I am thinking it was done when water was ingested though the carb.

Thoughts?

 

[Smokedtires]

Interesting. Do you have any plans for the carbon that is present? Is it a good idea to try and clean the piston tops or leave them be?

How was the flatness of your 6.0 Synder head? I checked mine tonight and the surface was less than 0.0025. Plans to paint it tomorrow.

I broke the sharp edge on the chambers. I've heard if the edge gets hot and starts to glow it can cause dentination.

 

[GPierce]

My head is flat. Could not see light anywhere under my steel straight edge.
I cleaned the carbon off the pistons. Probably not necessary. The piston that had the most carbon missing was stamped .100 so I wanted to make sure the rest of were the same. I also noticed the #1 intake valve had a hardened seat insert so I cleaned everything enough to find all the valves had hardened seats.

 

[J Franklin]

looks like water. After cleaning the block deck, check for flaws near where it is getting in. The block looks rough there now.

 

[Smokedtires]

Wow, what a difference. Thanks.

 

[Kurt in NJ]

a little oil makes carbon, more oil washes it off

 

[GPierce]

The engine has had no noticeable oil usage.
I will measure the circlularity of the cylinder with largest carbon free spot and see if possibly oil is coming up into the combustion chamber.

 

[CWPASADENA]

a little oil makes carbon, more oil washes it off

I agree.

It looks like oil passing the rings. have seen this many times thru the years.

Water getting into the combustion chamber can clean carbon off but ti is usually consistently across the whole top of the piston and not just along the edges.

My opinion,

Chris W.

 

[Synchro909]

Side tracking here but a good way to de carbonise your engine is to spray water into the intake of the carburettor at a fastish idle till the engine falters but does not stop. Repeat but this time, do it till the engine stops, turn off the ignition and leave it over night. When you start it next day, the moisture will have penetrated the carbon and the heat of combustion will cause it to instantaneously vaporise, blasting the carbon off the head and /or pistons and out the exhaust.

 

[Big hammer]

The same clean area is on #4 piston, not on #3, can’t see #1. Probably caused by swirling combustion flame, moving from 35 mph club to the 55 mph club might help with the carbon

 

[Bob Bidonde]

Photos of the head & pistons in my Model "B" engine after running a Synder's 6:1 head for 1000 miles.

 

[Flathead]

Slight head gasket issue eh?

 

[Big hammer]

Photos of the head & pistons in my Model "B" engine after running a Synder's 6:1 head for 1000 miles.

Nice and clean! I’m betting you’re not in the 35 mph club !

 

[old31]

Bob, on a 6.1 head i thought it was best not to have the gasket with the steam holes as yours shows around the middle stud. Yes, no?

 

[Bob Bidonde]

Old31, I tried putting copper head gaskets on with the seams up & down, and doesn't appear to make a difference on the Model "A's".

Big Hammer, Since blowing an engine last year, my wife has made me a member of the 55 mph max with cruising at 50 mph. I have a history of burning-out head gaskets like the one above on several different engines. I am now using the Kevlar coated steel head gasket. None of engines had cylinder bores more than 0.060"oversize, and most were 0.040". All of the blown gaskets are those for the 0.125 oversize cylinders, so they have inadequate material between the cylinders in my opinion.

 

[Jim Brierley]

That type of clean spot is normal on many engines. If you were to drive it harder, the spot would be smaller. Nothing to worry about.