Engine gurus, Where do I go next? Tore down 2270, Burning lots of oil Options

[DNHunt]

I drove 160 miles Wednesday trying to seat the rings. I used 3 1/2 quarts of oil. I would have made a Navy destroyer proud.

So, today I went looking for reasons. There was a small leak at the oil pump so, I resealed that and a little oil on the bottom of the oil filter. Neither could explain my oil consumption so off with the heads (and PCs too).

[DNHunt]

The engine goes like a bat outa hell but, it smokes like my old Mercury outboard.

Here's the intake port of # 3. All of them look the same.

[ws91420]

Not knowing your level of expertise my first thought were the ring gaps offset when you installed the pistons and did you notice burning oil in the exhaust

[DNHunt]

Cylinders 1 and 2 with oil in them.

[DNHunt]

Cylinders 3&4

[DNHunt]

Carbon buildup in chambers. Total mileage is 359 on the engine

[DNHunt]

Carbon on pistons. The rings have moved since I intalled them but, not a lot

[DNHunt]

The only thing I could see was all the skirts showed piston slap.

[Series9]

Wow! (IMG:http://www.914world.com/bbs2/html/emoticons/ohmy.gif)

It's almost like the pistons are too small for the cylinders. I'd take some measurements.

That's a LOT of oil in the barrels.

I'll be interested to see what develops.

[TimT]

QUOTE

It's almost like the pistons are too small for the cylinders. I'd take some measurements.

(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif) werd

what is the piston/cylinder clearance?

[Jake Raby]

Dave, that looks very odd, almost like the engine never warmed up!

It also looks like the oil had some contamination, because piston/skirt clearance issues usually severely damage the portion of the pistin directly under the oil ring, and totally smoke it.

The piston/cylinder clearance was set by the Nikisil platers themselves using the pistons used in the engine! We use .0015 as a standard clearance with these cylinders and pistons and this has never occured before.

I want to see those cylinders and pistons- something odd is going on here. With those same components I have never seen this before. My new 2316 has the same cylinders and same clearance, my pistons came from the same batch as Dave's and so did the cylinders.

[Reiche]

Sorry to see that Dave. Wish I was an engine guru.

[Jake Raby]

I'm also sorry to see it, but its one of the quirks that come along with being an "Engine builder".. Weird things happen that are sometimes never explained. When you take on the assembly of an engine to get the satisfaction of doing it yourself, you also must accept all the negative parts of the tasks at hand.

For those that don't want these risks, you can get it hot off the dyno- proven.

[IronHillRestorations]

I guess I'd start by checking the following:
piston to cylinder clearance, piston ring end gap, ring groove clearance, cylinder wall taper

Before you tore the engine down did you do a compression and leak down?

I'm guessing that you ran non-detergent oil? That used to be the generally accepted break in oil for nickasil cylinders.


Another from the hip thought would be if the engine was running very rich the rings may not seat properly.

[Jake Raby]

All the things mentioned in the last post were checked on this end, because he purchased a full custom kit from me..

I am with you on the rich running, thats the first thing that will cause this because it actually takes the oil from the rings.

Fuel is a solvent, not a lubricant.

It almost looks like the excess fuel increased friction, scuffed the cylinders a tad and helped wipe out the rings.... I bet the ring gap is excessive now, thats why I want to see them.

[Bleyseng]

Dave, pull off a set of rings and use feeler gauges to measure the ring end gaps, Please?


Geoff

[rick 918-S]

Air cooled is not my thing but, who did the heads? Check the stem to guide clearance. Do the type IV heads have oil seals on the top of the guides?
That's a serious burn deposit on the piston tops and combustion chambers!

The other possibility is the crank case venting. Check the inside of the far end of the vent tubes to see if there is raw oil coming through. I attempted to modify my crank case venting once. The method I used caused the vent hose to act like a drinking straw. I had a clear line for a vent hose and you could actually see the oil move through the line just as a huge plume of oil smoke came rolling out the exhaust!

Also, The scuffing on your pistons skirts could have come from the early injection problems you were experiencing.an over rich condition could have been washiing out the oil control ring.

One problem I see is too many modifications going on at one time. You have a freah big bore motor with the potencial to have many issues that will need to be worked through, then you attempted to install an untested injection system without a good solid base line function. (IMG:http://www.914world.com/bbs2/html/emoticons/screwy.gif) I admire your drive and persistence. Hang in there you'll get it! (IMG:http://www.914world.com/bbs2/html/emoticons/clap.gif)

[Jake Raby]

That was a full kit of mine.

As for too many mods at once- Not a chance internally... I would have ran carbs for a bit before doing the EFI install though.

As for the heads, they were prepped for Dave by Len Hoffman and passed my checks for approval. .0012 stem to guide clearance but no valve stem seals. (stem seals alter oiling on aircooled engines and we don't run them unless the valves are DLC coated, or made from Titanium)

I just looked up dave's ring gaps here..

They were .015 on the second ring and .016 That is text book for his combo.

There was nothing odd with this set up, nothing first time, nothing crazy... I think the fuel got it.

[Bleyseng]

It ran pretty much smoke free with the test carbs once we got the firing order right.


Geoff

[Jake Raby]

Thats what I was just thinking...

I think that fuel was the enemy.

It wouldn't be the first time I have seen that happen to an engine.. Happened to a 911 engine I built a few years ago and a 2270 that had a bad carb on it last year, while it was on the dyno.


Doesn't take long on a new engine..