motor teardown,verticle scoring in cylinders

[Billpan58]

went over to my motor builders shop today to look at disassembly,both cylinders have verticle scoring on walls, he thinks from impurities in oil,motor was completly rebuilt 20k ago, but started leaking[base gasket front cyl] this summer, always change oil regulary,plus run filter and cooler.neither of us can figure whats causing the above. another wierd thing he told me was that he miced the used kieth black pistons and they are 5 thousands smaller than they should be,he believes they shrunk.all in all, things dont look to bad in motor,s and s wheels and rods are still good after 32 years.Also he's going through the tranny, which is over 30 years. will need new main shaft[3 thousands under sized...wore] and some gear parts.this summer did leak down test and could hear escaping air in exhaust pipe[valve stems showed excessive carbon on stem base[tight in guides].motor did not have alot of power on a big long hill near my house. couple weeks will be back in business!Heads looked great no cracks,one broken fin he will have repaired,seats were replaced by local hd shop in early 80's still look fine

[jdpan]

What do the pistons look like? All in all, sounds like you got some good run time out of it resulting in normal wear..

[Billpan58]

pistons lok like they just came out of box,no wear on skirts,had carbon on top

[Cotten]

Bill!

The vertical scratches were most likely caused by hard carbon breaking off the piston crown and settling into the rings.

....Cotten

[Billpan58]

cotten,thanks for reply, any ideas for cutting down on carbon accumulation in heads. just talked to motor builder, says lower end looks all good[removed cam cover,inspected parts] did find a small chunk of carbon in breather valve. not sure how it got there,w/all the filters i have.Also have sifton prefilter in feed line.

[kitabel]

I haven't seen it, but the rings makes sense.
If it were grit in the oil, or coming in from the manifold, I would expect marks on the skirt as well.

[JR JOHNSON]

hi,whats a sifton prefilter?....with respect.....JR

[Cotten]

cotten,thanks for reply, any ideas for cutting down on carbon accumulation in heads. just talked to motor builder, says lower end looks all good[removed cam cover,inspected parts] did find a small chunk of carbon in breather valve. not sure how it got there,w/all the filters i have.Also have sifton prefilter in feed line.

Bill!

A "pre-filter" sounds like a bad idea, but anyway...

Carbon build-up usually is blamed upon excessive combustion chamber heat, where the fuel is burned too quickly, leaving a heavy residue. The higher the octane rating, the "cooler" and cleaner the burn (within limits of the compression ratio). When USA gasoline turned poor in the '80s, stock motors suddenly became too high of compression for common fuel, and such carbon formation began shortening the life of rebuilds dramatically.

The auto industry evolved combustion chamber designs to take better advantage of the fuel, but deposit problems remain.
So they turned to fuel additives, some Federally mandated.

One would think that all the digestive injector cleaners, detergents, and other unknowns tossed into the soup would constantly scrub out our combustion chambers, considering the way they make sparkplugs stay white.

However, if a motor is built to a compression that exceeds the fuel, you will always have a shortened fuse.

What compression are those hypereutectic pistons?

....Cotten

[jibhead]

i heard recently ,that its an approved carbon deposit remover for small piston engined airplanes too..... spray atomised brake fluid into the air intake when the motor is running.......

the carbon comes out the exhaust

[JR JOHNSON]

hi, just plain ol h20 works,spray it in, carbon comes out.....with respect.......JR

[Billpan58]

cotten i believe 8.5:1,going w/s and s pistons this time, maybe better to drop to7:1?

[Billpan58]

sifton prefilter has a metal screen plus a magnet built into it,you can take it apart to clean it.same inner dia. as oil line,plus the screen is not so small that it will impede oil flow. not sure how it could hurt, been running it for 7 years.

[john HD]

wouldn't a cow magnet in the oil tank do the same thing?

john

[Billpan58]

humorous responce and creative!

[panhead_kicker]

wouldn't a cow magnet in the oil tank do the same thing?

john

hhhmmm... non-farm boy here... I'll bite. What's a cow magnet?

then again, what's a henweigh?