I have a Magnum 46 that I pulled the head off of and found quite a bit of carbon build up in there. Not surprising because it had been run for a few years and always with some castor. It still runs strong though and has a good pinch at the top still.

Is it okay to simply polish away the carbon from the inside of the head and the dome of the piston without removing the cylinder? Exhaust ports are fine.

Thanks,

Ernie

I've done it that way several times...
Put the piston at TDC first...then do your scraping / cleaning...then drop the piston down a little to wipe clean any crud that might have been missed around the upper edge of the cyl. (I use Q tips )

It is better to run the engine with castor oil added in fuel than to run with fuel with pure syntetic oil..
It is cheaper to do a 'de-coke' than it is to do a repair!

Use a piece of hard plastic/nylon for your scraper to avoid scratches or gouges on the surfaces cleaned. Avoid leaving any carbon residue in or on the engine as it is very hard and can do a lot of damage in the wrong places.......

If the engine is running well, don't do anything. If carbon builds up too much it will be ejected out the exhaust. The only time I have been concerned is in a ringed engine when the ring or rings were stuck. Then I would take the piston out and soak the piston crown in Varsol.

Varsol? I have not heard of that since the late seventies; used to buy it in my own jug from the hardware store for 75 cents a gallon. Used it for everything (well, almost everything), including paint thinner, brush cleaner, parts cleaner, kerosene lamp fuel, and charcoal lighter fluid. I guess it is marketed in cans now for 12-15 dollars a gallon. Good old days!?!

I still have my Fox .35 and K&B .29 Greenhead CL engines from the fifties when I bought them new, big bucks then.

Cheers, and congrats on the hockey win.

Sincerely, Richard

Varsol??? That goes back a few years.

You can also fill the cylinder/crankcase with glow fuel and let it sit a few days.

I have been a little shy on leaving Glow fuel in an engine for a few days (the methanol attracts water). I've tried it once in the '70's and had rust. I have never known the fuel to dissolve carbon in an engine, I have used it to soften castor oil residue after an hour soaking.

I was thinking castor gum and you are talking about carbon deposits. Oops.

i always thought a little carbonization was normal.... just about all my glow engines run like tops and wouldnt be surprised if i pulled off the heads that i would see varnish or carbon formations... unless it is an extreme case i wouldnt mess with it,,,you may do more hard than good to the engine.

Great replies guys, thanks loads. Is it okay to reuse the head gasket a couple of times?

Thanks again,

Ernie

Yes, if it looks OK.

Heat it up and cool it in water, in order to make it softer.

Heating up the head for a while will vaporize the oil and will leave the carbon dry and easier to remove.

For cleaning, I use hard wood tools.
Surfaces don't need to end up shinning, but flush all carbon particles out of the cylinder and head.

Ernie,

We routinely polish the inside of the head and the top of the piston of our racing engines.

Some like to use Mothers metal polish, I prefer 0000 steel wool. Just do the inside of the head and the top of the piston, do not do the sleave or the sides of the piston, leave that alone. If you use 0000 steel wool take the piston out, and blow dry with compressed air to remove any steel wool residue after cleaning. Its very fine, but you still don't want it going through your motor.

I do this after about every 20 or so flights.

I use Scotchbrite to clean the top of the piston and head.No harm,great work.

Scotchbrite works also, thanks Turk1!

The typical green Scotchbrite from the super market works great for me also. Other grades of Scotchbrite (color coded) are available at auto refiinishing suppliers. Note that they are abraisive and the residue needs to be throoughly removed from the engine after cleaning.

if it's running strong and ok. why mess with it. You cant fix whats not broken ,

Eventually, it will not run strong and OK.
While carbon deposits build up, at least three bad things happen:

1) Heat transfer from the combustion chamber to the fins in the head is reduced.
2) Carbon crests and points stay incandescent (like the glow plug), and initiate the combustion at the wrong place and/or time. That messes up the time and place at which the expansion wave hits the top of the piston.
3) The volume of the chamber is reduced, which increases the compression rate, leading to detonation.

Good stuff! Would a micro butate torch be about right for heating the old head gasket, then cooling in water?

Thank again,

Ernie

No, Ernie, a torch is not the best for aluminum gaskets.

The heating should be non-local, but for the whole gasket at the same time.

A metal can over the top of an electric oven is perfect.

So you could bake your potato and gasket at the same time. Thanks,

Ernie