New Life for Columbo The '80s G, Man

[BA80]

Hmmmmmm........stock size? That means you're using used cylinders. Did you mic them for out of round and taper wear? Chrome (not just the shiny kind) molly doesn't like either.

[TopCatGr58]

I don't have anything to add to this discussion....but wanted to sorta hijack it a little with regards to ring installation....and a recent thread by RICHV that I've been posting in. I just posted about a theory I had as to why he's oil fouling his #2 cylinder. His engine was just rebuilt with honed cylinders, new rings, etc. He has great compression values in all 4, new valve seals as well, but still experiences oil fouling after about 20 or so miles of use.

I remember seeing a diagram /side view of the top 2 rings, and that they have an angled edge...the upper one to resist the compression pressure getting past it, the 2nd one positioned to help scrub/wipe the cylinders of excess oil downwards, along with the OIL rings. I remember there being stamps or indicators that showed which way was UP during installation of the rings. I was wondering if he had gotten the 2nd ring in his #2 cylinder upside down...that it wouldn't work as an oil wiper but possibly allow the oil to slip past it into the combustion chamber eventually fouling his plug?

Thoughts??Plausible??

T.C.

[BA80]

I don't have anything to add to this discussion....but wanted to sorta hijack it a little with regards to ring installation....and a recent thread by RICHV that I've been posting in. I just posted about a theory I had as to why he's oil fouling his #2 cylinder. His engine was just rebuilt with honed cylinders, new rings, etc. He has great compression values in all 4, new valve seals as well, but still experiences oil fouling after about 20 or so miles of use.

I remember seeing a diagram /side view of the top 2 rings, and that they have an angled edge...the upper one to resist the compression pressure getting past it, the 2nd one positioned to help scrub/wipe the cylinders of excess oil downwards, along with the OIL rings. I remember there being stamps or indicators that showed which way was UP during installation of the rings. I was wondering if he had gotten the 2nd ring in his #2 cylinder upside down...that it wouldn't work as an oil wiper but possibly allow the oil to slip past it into the combustion chamber eventually fouling his plug?

Thoughts??Plausible??

T.C.

You are absolutely correct TC. There should be a dot indicating the top of the ring. However, the point I was trying to make is chrome molly rings MUST have a perfect cylinder wall to seat properly. They are very hard metal and wear well but won't conform to irregularities easily like cast rings do.

Brand new engines and bored engines with the pistons fitted properly chrome is the way to go because it lasts longer but reringing a used engine the cast will seal up and work great. A lot of expensive experience behind that statement.

[BA80]

I don't even know if cast rings are available for these engines but I do know these things about moly rings are true.

[3Phase]

T.C.,

It's possible Rich put a ring or two upside down. The marks (it's a letter on my new rings, not dots) on the Top and #2 rings are easy to see if you know to look for them, if you don't then the rings could be installed in all sorts of interesting combinations. That #2 bore and piston in his engine almost looks cleaner than mine is right now and it hasn't even been fired up yet! Naturally, the picture he took is blurry on the #2 bore but I didn't see any marks from a mis-mounted oil Expander ring. The cylinder wall finish and the rings/lands might have been mangled by fuel washing though, like I said, the picture is blurry on the #2 bore.


Greg,

Yep, I checked for taper, wear, and out-of-roundededyness.

I got this set of 2H7 jugs with pistons and rods from Andreas. There was barely any wear at all in the bores and the ring end gaps for the original rings were all really close to the minimum spec. even at the top and bottom -- unworn -- portion of the bores. I might have been able to re-use them but I found some pictures on the 'net that match up pretty well with what happened to the mobile mosquito-fogger, erm, engine on the Colorado Rally so I'm pretty sure that re-using used rings is what killed it.

The used rings weren't sharp enough to cut/break the new 'peaks' the hone made in the bores even with only ~18K on them so they just bent and smeared the metal into the 'valleys'. That caused the weird contact and blow-by patterns and along with the ring/piston/cylinder wall seal and lube failure, it hammered the you-know-what out of the piston rings, the ring groove lands and destroyed the pistons. I'd rather not do that again.

.

[BA80]

Yep, you might have been better off to have just broken the glaze on the cylinder walls rather than honing with the used rings.

What you're describing sounds like the rings weren't making good contact with the cylinder walls so they couldn't transfer the heat. It just overheated the pistons and rings and she burnt up. Surprised you didn't end up with a hole in a piston or 2.

[3Phase]

Ouch....

Time for a break: sliced my finger good in the #1 intake port while I was washing the head down with hot water. Dummy....


Anyway -- the engine was pumping out a quart to a quart-and-a-half of oil every fifty to a hundred miles all the way to Colorado and back to Utah.

If it'd been burning the oil it would have got hot and been pinging like crazy when the octane rating went through the floor and equaled whatever octane the current bottle of 20W-50 oil had instead of unleaded regular gas but it never pinged once, even at the top of Pike's Peak.


Darn, so much for engine work this evening.

.

[BA80]

Time for a break: sliced my finger good in the #1 intake port while I was washing the head down with hot water. Dummy....


Anyway -- the engine was pumping out a quart to a quart-and-a-half of oil every fifty to a hundred miles all the way to Colorado and back to Utah.

If it'd been burning the oil it would have got hot and been pinging like crazy when the octane rating went through the floor and equaled whatever octane the current bottle of 20W-50 oil had instead of unleaded regular gas but it never pinged once, even at the top of Pike's Peak.


Darn, so much for engine work this evening.

.

There's only one way the oil can get out if it's not leaking out of the case and that's through the combustion chamber.

BTW Scott, oil would RAISE the octane of the fuel by making it burn slower.

[3Phase]

There's only one way the oil can get out if it's not leaking out of the case and that's through the combustion chamber.

Yep, most of it was pumping straight up the cylinder walls on #3 and straight out the pipe in a cloud of unburned fuel and oil vapor.

BTW Scott, oil would RAISE the octane of the fuel by making it burn slower.

I used to think so too but oil actually lowers the octane, that's why oil-burners ping. The volume of oil that was going through the #3 cylinder didn't leave enough volatiles from the fuel/air mix for the spark plug to actually light on fire and burn, it all just came out the exhaust and got the saddlebags, the bike and me a little oily.

On the bright side: the heavy detergents in the gallons of hot diesel oils and 20W-50 pumped through it cleaned up the inside of the right-hand exhaust headers and the muffler. I should probably be soaking the left-hand exhaust in hot oil while I'm working on the engine, get it all cleaned up and shiny to match the other pipes.

.

[BA80]

https://en.wikipedia.org/wiki/Octane_rating

HEAVY oil burners will knock but light oil burners will seem fairly normal. (a quart every 100 miles or so)

So, you also had a misfire?

[3Phase]

https://en.wikipedia.org/wiki/Octane_rating

HEAVY oil burners will knock but light oil burners will seem fairly normal. (a quart every 100 miles or so)

So, you also had a misfire?

Yeah, you could say that. It was basically a XS850 with an optional 275cc oil-fogger. Every now and then #3 would sort of light off but mostly it just put oil out the pipe. A lot of oil.

.

[3Phase]

Closer to launch day

And the jugs are on with some of that serious sealer 1207B by Threebond instead of a base gasket. I used a junk head to torque the jugs to the case so the sealer will set correctly and I can get an extra eek of compression without the gasket.

I finally managed to scrounge up enough good parts to finish up one good 2H7 head for the engine this afternoon too. It's sitting on the workbench now with WD-40 in the combustion chambers and I'll find out tomorrow if I got the valves seated or if they're going to leak.

I used a HeliCoil Sav-A-Thread insert to fix the stripped #2 spark plug hole. It's not as good as welding and re-tapping or even a Time-Sert but it can be made into a pretty decent repair with the head off the engine. If it doesn't hold up I'll toss it in the scrap pile and find another head that doesn't have that problem (it'll have its own set of new problems!).

.