Piston rings not sealing?

[I'm BLUE]

I like it so far, we'll just have to see. It is a little bit more expensive, but the higher ZDDP content(as Mike mentioned) is better for our engines than just the regular, off the shelf stuff.

 

Cool ! ,,, yeah , I was looking to switch to the Delco 15w-40 just for the reasons you mentioned of the ZDDP , and hopefully a touch better luck with any oil consumption/control in my current L-Series in my possesion ,,, but to be honest mostly for the ZDDP ,,, :) ,,, I typically use Valvoline Motor Oil ,,, Red and White Bottle changed often with Napa Filters ,,, on an off-note,,, will be switching to Redline 75w-90 for the ZX trans soon !

 

Info Appreciated as always ,,, :) ,,, sorry for threadjack

[MicroMachinery]

No worries. Free info FTW!!!

[MicroMachinery]

So today I drove the pickup up to the Ropes Course I work at seasonally, and drove it home. Felt fine the entire way. Just for fun, I checked the compression as soon as I pulled in the driveway.

 

90/175/175/178

 

[Farmer Joe]

no effin way...

 

what the hell happened? i got all happy and had a smile on my face reading about it being okay..

 

and then you pull this on us?

 

thats shitty.. i dont understand that. could the rings maybe be rotating themselves? is that possible? :blink:

[I'm BLUE]

Crap !!!!! :(

[datzenmike]

Took the 720 up to Portland today to drop off some parts. Got to my brother's house and borrowed his compression gauge just for grins and giggles...

 

195/205/204/212

 

 

 

I'm smiling now.....

 

Maybe the rings were stuck. High detergent cleaned them.

[MicroMachinery]

I'm smiling now.....

 

I'm not :angry:

 

So today I drove the pickup up to the Ropes Course I work at seasonally, and drove it home. Felt fine the entire way. Just for fun, I checked the compression as soon as I pulled in the driveway.

 

90/175/175/178

[albyneau]

Kinda been following your plight. Couldn't sleep, so here I am... Cast iron rings, I assume? At the top of this thread you said you had a 45^o crosshatch pattern~ is that in reference to the bore's C_L? Or 45^o between each up/down pass? If the former (45^o frombore's C_L) that's too steep and it could cause ring rotation. IIRC you also didn't say what grit stones you used, and I'm praying you won't tell me you used a ball hone glazebreaker. Ball hones "fall" into cylinder wall variances (ring ridge, etc.) and make it look pretty @ assembly, but in fact distort the bore even more. In the case of the ring ridge, the top ring's being forced to expand/contract into the bellmouth created from past wear- and aggravated with the ball hone. This constant in/out flexion literally forces the ring to adapt to a different bore on the fly at EVERY piston stroke. If this be the case the ring will fail almost exactly straight (180^o) across from the end gap.

 

And lastly~ did you use a quality ring expander? Cheap ones (or twisting the rings on) can exacerbate rotation, reduce ring/piston life, and if twisted enough can also lead to ring failure....

That sudden last crash back down to 90psi is not a good sign. Park it, test it, fix it ASAP~ lest the damage be irreversible.

Without seeing the motor in front of me that's the best I've got for now. Startin to get tired~ hopefully I forgot to mention something that resembles good news.

 

Good luck~

Scott

 

P.S. Is that the same gauge you used last time you got a low reading? Wouldn't it be nice if that's all it is... :rolleyes:

[datzenmike]

One of those testers is wrong. Get a third opinion!!!!!

 

The fact that it's always #1 is troubling for sure. How can a bad tester tell which cylinder it's on?

 

If this is a screw in type is it sealing properly?

The other gauge was it a screw in type?

Why would it work better, or was it?

[MicroMachinery]

I had considered for a second that it was the compression tester. The test I ran yesterday was the tester I had used previously. It is an older tester, but has never let me down as of yet(except when the schrader valve went bad, which was replaced). Another thing that directs me away from the compression tester, is that you can feel/hear the difference in resistance the compression causes in a cylinder with high or low compression(I do this with all the spark plugs out). A cylinder with higher compression with give you a more labored, higher pitch whine as you crank the engine over. A cylinder with lower compression gives a less noticeable, lower pitch sound; more like the engine just spinning over. Up at my brother's house, all 4 cylinders sounded exactly the same as I tested each one. To satisfy my disbelief, I tested each cylinder twice, and the problem cylinder, #1, I tested 3 times.

Also, after driving a distance, I am able to tell just through my fingertips that #1 cylinder plug is alot lower temperature than #2-4. I can comfortably hold the plug in my hand, vs the other 3, which it becomes a bit too warm to clench in a fist. Had I not had the high readings the other day, I would be able to write this off as a broken ring. But now that that has happened, I don't know what to think.

[MicroMachinery]

Kinda been following your plight. Couldn't sleep, so here I am... Cast iron rings, I assume? At the top of this thread you said you had a 45^o crosshatch pattern~ is that in reference to the bore's C_L? Or 45^o between each up/down pass? If the former (45^o frombore's C_L) that's too steep and it could cause ring rotation. IIRC you also didn't say what grit stones you used, and I'm praying you won't tell me you used a ball hone glazebreaker. Ball hones "fall" into cylinder wall variances (ring ridge, etc.) and make it look pretty @ assembly, but in fact distort the bore even more. In the case of the ring ridge, the top ring's being forced to expand/contract into the bellmouth created from past wear- and aggravated with the ball hone. This constant in/out flexion literally forces the ring to adapt to a different bore on the fly at EVERY piston stroke. If this be the case the ring will fail almost exactly straight (180^o) across from the end gap.

 

And lastly~ did you use a quality ring expander? Cheap ones (or twisting the rings on) can exacerbate rotation, reduce ring/piston life, and if twisted enough can also lead to ring failure....

That sudden last crash back down to 90psi is not a good sign. Park it, test it, fix it ASAP~ lest the damage be irreversible.

Without seeing the motor in front of me that's the best I've got for now. Startin to get tired~ hopefully I forgot to mention something that resembles good news.

 

Good luck~

Scott

 

P.S. Is that the same gauge you used last time you got a low reading? Wouldn't it be nice if that's all it is... :rolleyes:

 

I'm really not sure what you mean by 45 degrees from each up/down pass, or bore CL. The pattern is a criss-cross, 45 degrees from each other, as I have learned and was told throughout the years.

 

In regards to which hone..

This was lent to me from a friend who is a machinist. He told me this is what I needed for what I was doing. I am not a machinist, nor did I feel like that information would be of any consequence to me, so I opt to take the professional's word for it. I had a 2nd opinion from another friend who has been building race motors for 30 years. I asked him to oversee my work, and he couldn't point out any errors in the equipment I used, or in my methods.

 

I used a ring expander that I bought a few years back. I've used it a number of times with success. I'm not sure how the quality of it would be of consequence, as long as it was spreading the rings apart enough to get the ring onto the piston; could you please enlighten me? I don't twist rings into place. That's a no-no.

 

I probably will just yank the motor, as these up and down roller coaster readings are starting to make me emotional towards the engine. I made the statement last night, "I hate my LZ22", which to me isn't even rational. There's no reason a piece of machinery should make me upset or angry, which is why I walked away from it 6 months ago in the first place.

[MicroMachinery]

Disturbing. This afternoon, I ran the truck a little bit, then checked the compression:

 

160/175/175/174

 

Since I was not sure, I tested #1 3 times. Came up the same every time. I drove it to my shop on the other side of town and tested it there.. same. After that, I took it for a drive up through the hills, heavy on the RPM's(3-4k), then came back. Shut the truck off immediately and pulled the plugs to check the compression once again:

 

120/174/175/175

 

 

A couple people have suggested a broken ring. If a ring was broken, I wouldn't think that there would be compression at all; or atleast it would be consistently low... also, it appears that even though I now have compression in the #4 cylinder, there is still oil being burned there. And yes, I know how to install oil control rings, and installed them correctly.

[datzenmike]

Valve seat, sticky valve, worn guide, broken guide?

 

Do a leak down and listen at the tail pipe for hissing.

[Sealik]

I'm sensing your anguish.... :console: .... :D

 

From research into my lame LZ...I was going to suggest cylinder taper, which has a tendency of rotating the rings..in turn, affecting your compression readings???

But...I see you checked that already.... :D

 

Leakdown test as suggested....

[pocket rocket]

is it still using oil?

 

if not, stop testing the compression & just drive it.

You might end up wearing out the spark plug threads.

 

In fact, after all you've been through I would go & flog the f**k out of it.

:lol: :lol:

May not (probably won't) fix the problem, but you will feel a whole lot better:lol: :lol:

[MicroMachinery]

is it still using oil?

 

***

In fact, after all you've been through I would go & flog the f**k out of it.

:lol: :lol:

May not (probably won't) fix the problem, but you will feel a whole lot better:lol: :lol:

 

 

Still using oil. Now to punish her :devil:

[MicroMachinery]

The compression has come up on #1 cylinder.. it's still kinda bouncing around, but #1 and #4 are still burning oil. I don't think that's going to correct itself.

 

I can only figure that it happened during break-in when I had the 32/36 on. It ran pretty lean with that dinky carb, and the #2 and #3 cylinders got the lion's share of the fuel.. #1 and #4 must have just gone lean and monkeyed up my rings.

[I'm BLUE]

errrrrrrrrrr crap ,,, :(

[HRH]

Think it's time to take it back apart and figure out what went wrong. Could be a valve but with the oil eating, I'm thinking the rings were compromised somehow. Did you check the cylinder for out of round? (Egg-shape) Usually not a problem on L blocks, but still possible on high mileage blocks.

[MicroMachinery]

Yeah, had it checked for out of round and taper. They were uniform from front to back.

[albyneau]

I'm really not sure what you mean by 45 degrees from each up/down pass, or bore CL. The pattern is a criss-cross, 45 degrees from each other, as I have learned and was told throughout the years.

 

In regards to which hone..

This was lent to me from a friend who is a machinist. He told me this is what I needed for what I was doing. I am not a machinist, nor did I feel like that information would be of any consequence to me, so I opt to take the professional's word for it. I had a 2nd opinion from another friend who has been building race motors for 30 years. I asked him to oversee my work, and he couldn't point out any errors in the equipment I used, or in my methods.

 

I used a ring expander that I bought a few years back. I've used it a number of times with success. I'm not sure how the quality of it would be of consequence, as long as it was spreading the rings apart enough to get the ring onto the piston; could you please enlighten me? I don't twist rings into place. That's a no-no.

 

I probably will just yank the motor, as these up and down roller coaster readings are starting to make me emotional towards the engine. I made the statement last night, "I hate my LZ22", which to me isn't even rational. There's no reason a piece of machinery should make me upset or angry, which is why I walked away from it 6 months ago in the first place.

 

First off, My humblest apologies for a slow response. I don't (can't) keep track of all my posts on threads, due to personal obligations~ currently have an 850/mo job w/ a 980/mo mortgage. I will endeavor to try to focus on, and keep up with, those tech-posts that are important to you, and all members.

 

First off, MicroMachinery, I must in all honesty, and in your best interests, offend your choice of machinists, and the guidance he's provided. Having no other way to phrase this~ he either doesn't want to be bothered by you, or he's an idiot. My apologies for my candor~ but you need to know the truth. Were he sincere in his efforts he would've as well loaned you a ring ridge cutter~ which by your photos was not used. When driving out the pistons the ring lands can be easily damaged if this tool is not utilized. The second ring seems to have left a bit of a groove. Some call this second ring a (secondary) compression ring~ but in fact it's primary function is that of scraping off most of what the oil control ring's let by. Remember some oil needs to get to the top ring...

 

Ball hones are utilized for the most part two purpose only~ as a short-term fix for a quickly-diagnosed broken ring, and to facilitate a quick sale once repaired; and to do a band-aid fix on worn compression rings and oil/compression blowby. As judging by your pics the hone angle is too steep~ the scratchmarks need to be 45^o between eachother~ meaning 22.5^o to bore C_L . At too steep an angle the honing can have a corkscrew effect~ causing the rings to rotate. Moly or chrome rings require an even lesser angle, and if installed on a too-agressive hone pattern will tend to rotate as well.

 

Yeah, had it checked for out of round and taper. They were uniform from front to back.

I'm not quite sure what you meant by this- front to back- but at this point I'd love to get my hands on your motor~!

Sorry~ that sounds bad~ but I hate it when people get steered wrong!

 

In closing, and in general terms, I loathe production shops who will profess their knowledge and expertise, yet point a budget-minded customer in the direction of mistakes only to pad their own pockets. I have dealt with this phenomenon my entire career~ and am striving towards opening my own engine shop to serve the CUSTOMER~ not my bottom line.

 

Peace~

Scott

[MicroMachinery]

Thanks for taking your time to respond. I appreciate it.

[MicroMachinery]

I finally figured out why my engine hasn't been cooperating; I simply have not been "challenging" it enough. I have hired a few "motivators" to educate her...

 

 

... she will be graduating from LZ22 School, and moving up to LZ23 University soon. That'll learn her :devil:

[wayno]

Z24 pistons huh, I sure noticed a differance going from the L20b to the LZ23, night and day seems like as good of an example to the differance as any, but I have 280Z valves in my W53 head, and the intakes in the head were ported to match the SU intake manifold. I am hoping to put that engine back in the work truck this weekend, it's hard to go backwards in power.

[EricJB]

I did just drop out the old oil today; it was black as soot. I know that when the SU's were flooding off and on, I had been running way overrich(I was way up in the mountains, so I had to drive it back that way). I know that fuel contaminated oil thins out and will be more prone to burning, so that's why I dropped it out. There was nothing unusual in the oil, except for the color. No flakes, nothing like that. I changed the filter as well.

 

 

 

Sorry I joined the party a little late. I read through this whole thread, and the one thing that jumped out at me was the rich mixture. A rich mixture will wash the cylinders down and the rings wont seat right. How long did it run rich? if the fuel problem is solved, it might still work out.

 

As mentioned by HRH and others, drive the piss out of it. If your planning on boring it out anyway, even if it has a broken ring, ( i'm not quite convinced) It will clean up on the rebore anyways.Chrome ring, rich mixture= long break in, if it recovers. Drive it like you would normally. dont baby it. It comes around or it doesn't. Breathe.