Cleaning the carbon?

Scrap it with a flexible piece of metal, like with the side of a feeler gauge or the non-sharp edge of a razor. Be carefull not to cut grooves on the cylinder in the area polished from the ring friction or the sealing surface with the head. Use some WD40 or kerosene to clean and soften the deposits.

After you have cleaned the cylinder, you have to send the cylinders to a machine shop to hone them slightlly (a cheap operation). This operation will restore the crossed pattern in the cylinder surface which helps the rings seat and retains oil to lubricate the cylinder walls, but more important, it removes the steps (one in the top and one in the bottom) between the polished and the unworn area of the cylinder. If you don't remove these steps, the new rings will break when trying to ride over them, because the new wear pattern won't match the old (you'll probably be installing some cylinder spacers bellow the cylinders to set the CR).

If the cylinders have a very low mileage, these steps may not be apparent. In this case, you may omit the honing and use some wet or dry (280 grade) paper with WD40 or kerosene to take of this step off. Follow the crossed pattern directions when rubbing with the wet or dry paper, and do not overdo it. Also rub the polished surface a bit, just enough to remove the glazed surface. Then thoroughlly clean the cylinders to remove any remains of abrasive material. This may not be the best way (I wouldn't want my engine being rebuilt this way), but works if you want the cheapest posible restoration that will last for a couple of years.

When you finish with the cylinders and have the pistons cleaned and bought new rigns, Check the ring gaps in their respective cylinders, as described in every repair manual. Then weight each piston with it's rings and pin. You have to make them the same weight (as close as possible) by removing material from the heavier pistons (inside the piston skirt near the edge you will see protrusions provided for removing material to equalize weight). Th is step will add to the quality of your rebuild as much as equalizing the volume of the combustion chambers and the CR of each cylinder. A well balanced engine will feel great, have good fuel consumption, last long, even if it is built from used parts.

Bill, '67 bug.

easy-off oven cleaner! No joke. Just be careful with 1) the fumes 2) try not to use on the heads as it reacts with aluminum and turns it black for some reason.

I thought this carbon acted as an oil seal? It will only build up again after a couple of thousand miles.

--Steve

I might use a thinner shim under one of the cylinders than the engine came with. So there's a risk of a ring smacking into some carbon.

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This is a good tip.

Oven cleaner contains LYE which is the same stuff in that smell 'hot tank' in the back of an automotive machine shop and super-good stuff for breaking down oil and baked-on crud.

BUT ONLY FROM STEEL OR CAST IRON.

Lye is sodium hydroxide. It will dissolve aluminum or magnesium.

When shopping for oven cleaner, see if they jellied brush-on variety is available in your locale. It's about 4x as effective as the spray-on stuff yet costs only half as much.

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When rebuilding an engine the repair & refurbishing of the shrouding is at least as important as proper engine assembly since those crazy bits of tin-ware comprise the cooling system.

To remove the old paint, all of the grime and much of the rust, simply boil the tin-ware in a stiff solution of trisodium phosphate, commonly available from paint stores. But for a bit of modern-day humor, do NOT buy the commercial product with "TSP" as the brand-name. TSP is the common acronym for trisodium phosphate but the joke here is that "TSP" (brand name) does not contain any... and sez so right there on the box.

Some years ago I posted a thingee about overhauling tin-ware and mentioned the standard cleaning procedure -- boiling the stuff in TSP. I got a lot of mail from folks saying it didn't, recommended trying lye (which works but is dangerous to work with). Turns out, they'd bought the box that said "TSP" on the label but didn't read the fine print.

So why is there no tsp in "TSP"? Because of the tree huggers. In some areas so much phosphate has found its way into the water supply that they've banned the use of it... except for farmers and painters and mechanics and so forth.

I dispose of TSP by dumping it on the compost heap, letting the microbe beasties eat it up.. which they do.

-Bob Hoover

Why thinner? The only rationalization I can imagine is even out the deck height - when the shims just happen to dimension properly.

I gotta find your old posting about that. The idea of boiling some of the larger tin bits brings up the image of a great big cartoonish cannibal's cooking pot suspended over a fire. Sure couldn't do it in the kitchen!

Anything that can go into the compost pile, does. Makes for good gardening later.

Under normal circumstance you would be right. But experience with this engine has taught me that it was very poorly put together. I'd crack the case and check out the mainshaft bearings and measure /everything/if I had the tools and experience and time to do it right now -- it's probably a chamber of horrors. But I don't have those needing things. So I'll match long pistons/cranks with short cylinders and vice-versa as needed to arrive at similar deck heights. The deck heights were probably all a bit more than I want anyway: I'm shooting for something close to

1.6 - 1.7mm, but with the shims the engine came with they were closer to 2.5mm.

Then I'll open up the heads as needed to lower and match my CR's. I expect to be opening the heads up a lot as initial rough measurements suggest the CR is running silly-high for the Wonderbus.

It's a small amount of effort to remove the carbon, thanks to the wonders of Easy-Off, and it will give me the freedom to mix 'n' match parts as needed w/o worrying about the piston bumping into the old carbon.

This won't help with decarbonizing, but let's not forget the good old pressure hose for degreasing big parts, like the interior of the fan shroud. I finally did mine at the car wash after soaking it with their own degreaser. The owner didn't mind a bit, and it's supposedly 'green'. The city regulates exactly what kind of soap, etc. car washes can use.

Car washes have degreaser?

The things you learn.

Some do. If they don't, then they might have 'whitewall tire' soak. Works very well.

I meant match long pistons/cranks with LONG cylinders, etc.

My heads are indeed toasted bread. Time for new.