Blowing oil update #3. NO broken rings
 

Awwww Hell!

I thought it would be cut and dry...

I felt my case vent and there was a definite pulsing (One per revolution, and a steady "blow" at 3000 RPM. I then compared against a stock SC with 75k miles... it just had a slight back and forth feeling, normal, even at 3K RPM... Plus I smelled raw fuel vapor coming out of the case.

So I figured, must be a cracked ring...

Pulled the motor and the heads, cylinders, NO CRACKED RINGS, no upside rings...

They all looked good, motor looks perfect. I noticed that one cylinder MAY have had the compression rings and oil ring gaps almost lined up...

So NOW WHAT? :mad:

(se previous threads in this forum for more discussions... Newly built motor 400 miles, 10:1 compression and boattailed case, new valve guides, etc..)

Did you run a leakdown test before pulling the heads? If so, was the cylinder with the lined up rings leaking?

a bad guide(s) can blow pressure into the crankcase. they would have to be pretty worn.

JW. EBS did the valve guides, they are brand new so I doubt that this is it.

I was not able to do a leakdown, just a compression test. Cylinders came out 152, 153 on all of them...

Chris,
Aligned ring gaps can definately cause blowby. Gaps should be staggered 120 degrees with no gaps near the exhaust side of the barrels. I think you found the problem, especially if the two aligned gaps were the compression rings.

They were...

Alright Chris, I have too ping the collective knowledge of the BBS (mostly for my own education).

Even with newly machined and assembled heads, could the valves allow blow-by (blow-back?)? On a motor that has less the 1K miles, is it normal to see any carbon residue behind the intake valve?

I would expect to see fuel residue on the back of the valve, but with such low miles, could there be any carbon buildup behind/upstream of the valve, on the port walls?

Is it possible to set the valves too tight such that the valves are not seating properly at high temps, thus allow blow-by back behind the valve?

Souk;
Given that Chris's cams have a significant amount of overlap, I wouldn't be surprised to see carbon buildup such as you described. At least as long as it wasn't excessive.

I'm going to post a picture later. Hadn't thought of that john. I may try and set the valves that have this (not all do) just a hair looser to be sure...

"...could the valves allow blow-by (blow-back?)? ..."

The only path from the combustion chambers to the oil tank is through the crankcase (oil supply and breather hoses). The intake tract is on the other side of the engine and thus provides no pressurized connection to the oil tank. However, I believe it's venting to atmosphere in his engine. Besides, if a valve isn't closing for whatever reason, a compression/leakdown test would show that.

Perhaps a leakdown test might have revealed a compression loss path through the ring gaps, but combustion pressure are much higher than leakdown pressures and may not have shown much. As Werk I suggests, make sure the gaps are staggered during reassembly. You may wish to check/verify the piston-to-cylinder wall clearance as well (despite them being new) and make sure the rings aren't hanging up on their groove.

As an added suggestion, you may want to go through an engine break-in procedure once more.

Sherwood

Without leakdown, compression test data you have to many possible causes for this problem to be properly analyzed.

Note: Rings constantly rotate while the engine operates. Its unlikely they would all align, but possible. Even if they did it would only be temperary.

Could be a whole lot of things, even improper break in in which case NOTHING would look wrong. (unless you have a metalurgy lab at your disposal)

I talked to too many shops (including Kelly Moss and Cox) that said unless I had a broken ring, leakdown wouldn't show anything, nor would compression... Compression I did because I wanted the guage.

The cylinder pressures in combustion are so much higher than in either test, they told me that neither were likely to show much.

All gaps and clearances were checked before the engine was assemebled, and all parts were new. I'm going to reassemble, reset the valve clearances, and hope for the best.

Since there are no overt causes (tolerances, breakage, etc...) there is little else I can do... Anything more would require some pretty extensive and expensive measures.

I will go through the break in procedures again...

Just in case the rings failed to seat properly buy a grape type hone (about $50) and hone the cylinders for about one minute each. Use transmission fluid for a lube. Dip the hone into a can of tranny fluid, hone for about 15 seconds redip and continue honing. Use a variable speed drill running at about 300 to 400 RPM and stroke it at about once a second. The hone will put a new finish on the cylinder that should allow the rings to seat. No significant material is removed so you don't have to worry about taking to much out. OR have a shop do this for you.

don't hone any "sil" style cylinders. the exposed silicone molecules will be removed in the process.

JW, that's what I've heard... I haev Nikasil Mahle Cylinders. They only haev 500 miles on them, so I would guess they are still okay.

One question. Is it normal to see some vertical lines on the cylinder walls? I can see where the pistons are going up and down. I can't FEEL the marks, even with a fingernail, but I can see some slight wear. It's not the piston skirts, looks like it's from the rings...

kind of normal, as long as they are scuffs and not grooves.

Chris,
Double-check your fuel delivery system. Excess fuel can wash away enough cylinder wall lube to create this wear.

Sherwood

Sherwood... That would also coincide with the fuel smell from the case, so I've pondered that... but the plugs are clean above idle... Any way to really check that?

JW, they are scuffs, definitely not grooves...

"Any way to really check that?"

On a chassis dyno with appropriate A/F sensors in the tailpipe.

On-board: Wide range O2 sensor and accompanying circuitry.

Running carbs? Check float bowl fuel level; verify correct fuel pressure.

Sherwood

Well I know the fuel pressure is 4 psi, but haven't checked the float level though, worth looking into, thanks,

Chris, it really sounds like the rings have not yet fully seated. On the blowby situation... did you check the ring gap with the rings in their respective bores? This being new piston/cylinders, it would seem highly unlikely, but when all else fails, check all the possibilities.

The engine is mostly back together. Will have it back running this weekend mostly likely. I'll give an update then.

I'm in the process of planning oil tank baffles, just need a few more hours of MIG welding practice. LOVE my new MIG welder!

Okay, I've read this entire thread. I can't quite figure out what the problem is? Pulsing at idle you said? Fuel smell? Pretty vauge. Also, the engine probably isn't run in yet - takes about 1000 miles. I would have waited for 1000 miles before I tore anything down again...

-Wayne

Wayne, there were two other threads behind it that described the problem, but essentially it boils down to the fact that I was getting SO much blowby, and hence crankcase/oil tank pressurization that it was literally emptying my oil tank into the overflow tank (required for racing)

The motor is back together and I'm getting very similar air as before comign out of the case. It think now maybe the rings just haven't seated completely.

Just gonna deal with adding oil and draning the overflow tank for a few thousand miles. If it doesn't go away then, I'll look into this again.

Only problem is that I am getting so much oil out, that the overflow tank, well, overflows and spews oil out the breather. I added more slope to the oil-tank/breather connecting hose and made a small orifice to help keep the amount of oil getting into the overflow tank down.

During the initial engine break in its very important to do several FULL throttle accelerations and deaccelerations to seat the rings. If if this is not done it could take many thousands of miles, if ever to break in the rings. You can check eany auto tech book on this subjest to verify this fact.

If you have gone to far beyond the initial condition it may be almost impossible to get the rings totally broken in. The only way I know of is to do the honing operation I mentioned earlier to change this condition. If the cylinders are the type that cannot be honed you may be in trouble, but I am pretty sure I read that you have the kind that can be. Try it for a couple of races or thousand miles as is. If you do not have better luck then, try this honing step, it really does work like magic. It puts just engough of the type of cross hatch pattern in the cylinder of the correct type to seat the rings real good.

Snowman, I understand. Thing is -- I did this. I went through a series of full throttle accelleration and deccleration (in gear for reverse pressure as well).

1. I did a 20 minute cam break in at 2000 RPM.
2. I then took the car out on the road, and went full throttle to 4000, then back down to 2000, then up to 4500 and back down. Then let the engine settle for a few minutes by just driving while varying RPM. Then up to 5000 and back to 2000 RPM, etc.. etc... HARD acceleration all across the rev range and back down. Had 50-75 good variable accleration miles on it, then off to the race track. First session was a mild practice session.

There is still bad luck. It could be that the rings just do not want to seat for some reason, unknown. Go for it for a while, couple of races or 2000 miles. If then you still feel there is a problem try the hone thing.

Chris,
I guess you've tried everything else and the rings indeed may not have seated, thus the excess blowby. However, instead of reducing the orifice passage from the tank to the catch tank, I'd increase the ID as much as possible. A larger ID (3/4" min.) lets the crankcase breathe easier, reduces air velocity and allows better separation of oil and blowby.

How about using a straight 30 wt. oil during this break in period rather than any fancy multi-vis oil? Leave out the oil additives and verify the oil level is a quart (maybe two) or so below the "full" mark on the dipstick.

Sherwood

Hmmm... Both good ideas! THanks.

Sherwood, can you recommend a brand?

is that brass restrictor sleeve in the breather hose from the tank? it helps to keep oil from passing, but allows vapors to escape.

JW, There was no restrictor from the tank to the breather before....

On a suggestion I have added one. THe hose is about 3/4" ID. I made one by inserting a coupler with a washer welded to it. Essentially reducing the diameter at that point to 1/4". The coupler is positioned halfway up the arc made by the hose between the tank and breather neck to allow the oil to run back into the tank.

"can you recommend a brand?"

Others might recommend continuing with 30 wt. non-detergent oil. I say just use some HD 30 wt. Castrol or equivalent, but that's just my opinion.

I would place oil separator devices in the tank area (either oil tank or catch tank) where the vapors have room to move rather than placing a restriction in the breather hose.

Sherwood

i'm talking about the factory tube type restrictor with curly brass wool packing that was in the breather hose/filler neck originally.

Huh... I've never seen that one... Do you think one could be fabricated?

Okay, I've thought about this some more. Here is what I recommend:

- Run compression check again
- Run leakdown check
- Run a CO/HC check

If all three come back normal, then you're fine - your rings have seated, and your engine is running well. The CO/HC check will be the final indicator - if the HC are low, then you're getting good combustion.

I'm going to go out on a limb here, but I think the problem may be with your oil tank setup. I have no idea what you're using, but I think you may have it plumbed incorrectly. If all three of the above tests check out okay, then I would look very closely at your oil tank system.

-Wayne

http://forums.pelicanparts.com/uploads/IMG breather.jpg

the hose from the engine breather does go to the side of the tank, and the hose from the filler neck to the catch can, right?

JW. Yes that is correct.

Wayne, The pickup is in the rear, return to the front leading to oil filter. The crankcase vent hose goes to the side of the tank near the top and above the internal oil sperator, then the tank vent from the side of the filler neck goes to the catch tank.

The blowby, in and of itself was not necessarily concerning me too much, it was the fact that I was getting huge amounts of oil into the catch tank, so much so, that my oil levels were getting dangerously low during long track sessions... If I could fix that, blowby be damned.

The CO/HC test is a good idea though! I'll have to check that after a few hundred miles...

your restrictor, with the 1/4" hole may not be full flow, that is pressure may be forming behind it, causing any oil in the vicinity to be forcefully blown thru the hole. the OE unit is full flow, but holds oil droplets back. one down at the filler neck, and another at the top of the arc might help.

JW. Good point. I just added the restrictor, haven't run the car with it, so it wasn't causing the problem. Makes me think I should remove it and put in something similar to the factory one then.