F355 Piston ring seating into cylinder walls? - Ferrari Life
 
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post #1 of 20 Old 02-23-2015, 09:42 AM Thread Starter
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Piston ring seating into cylinder walls?

Hey Guys,

So my buddy has told me and I've read that typically you must replace piston rings and hone a cylinder bore if removing pistons from a motor that is beyond the break in.

In the case of the 355, given the cylinders have a Nikasil coating and honing of the cylinder wall is not an option, it is a requirement to install new rings if removing the piston from the cylinder?

It will be a week or so before I am at this point. The goal is to inspect and only replace what is needed.

Just thinking ahead and looking to learn.

Thanks.
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post #2 of 20 Old 02-23-2015, 10:37 AM
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Dave, your new rings should have a fresh, deglazed plateau finish on which to seat. For Nikasil, either a ball type hone (FlexHone) with 240 grit aluminum oxide abrasive, or a green Scotchbrite pad can be used to condition the surface.

If you opt for the FlexHone, use an old head gasket to protect the soft, uncoated tops of the liners and your deck surface as the abrasive balls can scratch these surfaces.

Also, a brand new FlexHone will want to "shed" some of its abrasive straight away, so break it in on a piece of pipe before you use it on your cylinders.

Brush Research recommend to keep the hone well lubricated, but if possible, I'd have a continuous oil flush going to wash away the grit, etc.

I'd be interested in seeing pics of your liners before & after you deglaze them.

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post #3 of 20 Old 02-23-2015, 10:41 AM Thread Starter
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Hi John,

I knew you would reply and was awaiting it

However, please re-read what I wrote. I am asking if it's a requirement to re-ring if I pull the piston out.

Even if the cylinders look good, I still may wish to inspect the current rings / pistons.
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post #4 of 20 Old 02-23-2015, 12:58 PM
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It is best to remove the liner & piston as an assembly, when not replacing the rings. Based on your compression/leakage tests, you should be considering replacing at least a couple of the ring sets. Based on the poor condition of everything, it'd be wise to plan on replacing all the rings and taking the time to measure the liners and fully inspect all of the insides for other signs of abnormal and excessive wear/damage/failure.


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post #5 of 20 Old 02-23-2015, 01:17 PM Thread Starter
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Josh, thanks for your reply.

I suspect (note, suspect) that my poor CC and LD is a result of top end problems (carbon, etc on the seats). I could hear the leaks while doing the LD coming thru the exhaust.

I am planning to measure the cylinder walls - I suspect I'm not going to find problems there - again, only a hunch at this time.

As the liners are pressed into the block, it seems like removing them with the pistons as a subassembly and reinstalling them as a sub assembly would be a really neat trick. I can purchase a set of rings for $800 so that being said, I would not mess around removing the liners.
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post #6 of 20 Old 02-23-2015, 01:19 PM
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Dave, as Josh said, if this is the engine with the dodgy compression & leakdown readings you ought to replace at least a couple sets, and you know the old mantra "....while you're in there....."

BTW, if you contact Mahle aftermarket, they can probably fix you up with rings at much better prices than Ferrari....

Once you get the heads off, you can do a leakdown on the lower end to see if you really need to rering.

'99 550, Rosso Corsa / Nero, S/N:114654, Assy: 31836, Engine: 52084

High mileage, low compression, and missing on a few cylinders.....just like my cars.

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post #7 of 20 Old 02-23-2015, 02:10 PM
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Most of us have made up our own tooling to accommodate the process of driving out the liners, while the pistons are in situ. It's not as tricky and clever as you'd think as the liners aren't pressed in with interference.


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post #8 of 20 Old 02-23-2015, 02:22 PM Thread Starter
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Originally Posted by ECSofVirginia View Post
Most of us have made up our own tooling to accommodate the process of driving out the liners, while the pistons are in situ. It's not as tricky and clever as you'd think as the liners aren't pressed in with interference.
Josh, respectfully, when I read your post I really thought you were sending me on a fools errand.

It sounds like a ridiculous idea at best. The WSM states to freeze the liner with liquid nitrogen prior to installation and that is also what we did when I worked at GM.

I just can't understand why in the world I would remove and reinstall a liner unless the problem was the liner. As I sated, I can buy a full set of rings (aftermarket) recommended by a Ferrari dealer for $800.00. Before I would mess with removing liners, I would just spend the $800.00.

I posted this thread to ask if the pistons can be removed without the need to re-ring. That question was a result of the marriage between the rings and cylinders of other motors but knowing this one has the hard coating, I was not sure it applied.
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post #9 of 20 Old 02-23-2015, 02:50 PM
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Dave as said previously i dont think anyone who has done an engine has actually done that. I know it ws not recommended to us then. I have but the engine was only 13.5 to 1 compression with nikasil liners and it did work. Saying that and not knowing ferrais tolerance vs the race bike i would not do it. Mostly i would not do it because the motor cycle engine was itaken out in a few hours and if id didnt work was easy to remove again. i would check the the leakdown as stated above and if its good i would not do the rings. We also used a used ball hone and put a very light crosshatch. Like yourself and partial ocd if i was going to do one set of rings i would do them all just to freshen up the engine. We did a light ball hone so the rings would reseat. Everyone thinks ferraris are state of the art but the race bikes i worked on 25 years ago had higher compressions and were developing 155 rwhp using 750 cc. Just my opinion and i know you know that. We did it because we were young, cheap, and trying to gain an edge on our friends and our time was cheap.
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post #10 of 20 Old 02-23-2015, 02:55 PM
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I guess i should add the dyno results before and after made no (0) differance so we did not do it again.
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post #11 of 20 Old 02-23-2015, 04:53 PM
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Quote:
Originally Posted by dave rocks View Post
I just can't understand why in the world I would remove and reinstall a liner unless the problem was the liner.
Dave, at least put your borescope into the main coolant "plenum" at the top of the block (circled in red below) and have a look at the backsides of the liners which are facing inboard. If you see any pitting, you might want to pull those liners for a closer inspection. My pic is of my 550 block, but your engine & mine use the same water pump, so I'm pretty sure you must have the same coolant passage as this.

Next pic is of the interior of that main coolant passage, and you can see the rectangular slots (2 per cylinder) where you should be able to see the backsides of the liners. Many of mine had fairly deep cavitation pits on this inboard side.
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'99 550, Rosso Corsa / Nero, S/N:114654, Assy: 31836, Engine: 52084

High mileage, low compression, and missing on a few cylinders.....just like my cars.

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post #12 of 20 Old 02-23-2015, 05:14 PM Thread Starter
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Hey John,

I appreciate the advice. I gotta be honest though, I'm already going really deep - I don't want to replace liners. I really believe the bottom end will be good.

And, I could not help continue to think about what Josh said. Even if I pulled the Pistons and liners as a sub assembly, I see a few problems related to the marriage of rings to cylinders.

First, unless I locked the piston to the liner, as soon as radial rotation would occur, the seal marriage would be gone.

Second, if I could lock the piston to the liner, no way would I be able to reinstall and maintain the same radial orientation unless the liners are keyed and I doubt they are.
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post #13 of 20 Old 02-23-2015, 05:32 PM
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Dave,


The liners are sort of keyed. See picture.
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If you are going to tell someone how to remove a bolt you should at least know which way to turn the wrench.
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post #14 of 20 Old 02-23-2015, 05:50 PM Thread Starter
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Quote:
Originally Posted by john85QV View Post
Dave,


The liners are sort of keyed. See picture.
Thanks John. As you indicated, really not keyed as much as the flats are there to accommodate the flange while getting the cylinders close together.
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post #15 of 20 Old 02-24-2015, 06:21 AM
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Originally Posted by dave rocks View Post
Josh, respectfully, when I read your post I really thought you were sending me on a fools errand.

It sounds like a ridiculous idea at best. The WSM states to freeze the liner with liquid nitrogen prior to installation and that is also what we did when I worked at GM.

I just can't understand why in the world I would remove and reinstall a liner unless the problem was the liner. As I sated, I can buy a full set of rings (aftermarket) recommended by a Ferrari dealer for $800.00. Before I would mess with removing liners, I would just spend the $800.00.

I posted this thread to ask if the pistons can be removed without the need to re-ring. That question was a result of the marriage between the rings and cylinders of other motors but knowing this one has the hard coating, I was not sure it applied.


I believe I understood your question just fine and answered it accordingly. If you notice, your trusty WSM makes no mention of what to do when re-using the piston rings. The expectation has already been set, in the WSM, that when you separate the piston from the bore, replace the piston rings.


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post #16 of 20 Old 02-24-2015, 07:06 AM Thread Starter
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Originally Posted by ECSofVirginia View Post
I believe I understood your question just fine and answered it accordingly. If you notice, your trusty WSM makes no mention of what to do when re-using the piston rings. The expectation has already been set, in the WSM, that when you separate the piston from the bore, replace the piston rings.
Josh, I'm sure you will agree that the WSM has information scattered around in multiple sections. For example, the timing details are specified in a table that is not in the timing section.

That said, I do not see any comments stated that rings should be replaced when separating them from the bore - but, I may have just missed it. It may be in the electrical section for all I know

If you can point me to the page, I would appreciate it.

Last edited by dave rocks; 02-24-2015 at 07:14 AM. Reason: I can't spell for crap...
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post #17 of 20 Old 02-24-2015, 09:34 AM
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Quote:
Originally Posted by dave rocks View Post
Hey Guys,

So my buddy has told me and I've read that typically you must replace piston rings and hone a cylinder bore if removing pistons from a motor that is beyond the break in.

In the case of the 355, given the cylinders have a Nikasil coating and honing of the cylinder wall is not an option, it is a requirement to install new rings if removing the piston from the cylinder?

It will be a week or so before I am at this point. The goal is to inspect and only replace what is needed.

Just thinking ahead and looking to learn.

Thanks.
The only reason ring replacement would be necessary is if there was a ridge at the top of the cylinder that caused damage to the rings when you removed the pistons.

Otherwise I can see no reason for replacement.

If the bottom end leaks down good with a deck plate I wouldn't remove them personally. As for measuring, you will be able to check anything of most importance (top of cylinder). Not much cyl pressure at BDC but you could leak it down at BDC as well if you are concerned.
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post #18 of 20 Old 02-24-2015, 09:39 AM Thread Starter
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Originally Posted by INTMD8 View Post

If the bottom end leaks down good with a deck plate I wouldn't remove them personally. As for measuring, you will be able to check anything of most importance (top of cylinder). Not much cyl pressure at BDC but you could leak it down at BDC as well if you are concerned.
I agree. However, I am suspecting heavy carbon build up and cleaning the pistons in the bore will be a challenge. I also would like to flush the block. So, I'm still on the fence but another $800.00 for rings may be worth doing.
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post #19 of 20 Old 02-24-2015, 10:24 AM
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You're going to get different opinions on all of this, just like with everything else. Ferrari says not to hone the Nikasil liners, replace them. Benz for example gives a very specific procedure in which the Nikasil liners CAN be honed, as they aren't removable liners in those engines.


My experience is that Nikasil cylinders are particular when it comes to ring material and seating. If you're going to take the time to replace every little nut bolt, clip and washer, I don't see the value in skipping on something like piston rings. The safe bet is to leave it all as it is, or completely re-fresh it. There's rarely much value other than the up front out of pocket costs, when taking the middle road.


It's all moot until you know if the factory honing looks OK, whether there are any defects in the surface and whether the original rings are within wear limits. Still, since you have the luxury of doing this job at no labor costs and at your own pace, the value lies in going the extra mile and going through every last bit and making sure it's all spot on. Or so I would be led to believe anyway.


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post #20 of 20 Old 02-24-2015, 10:38 AM Thread Starter
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I can't argue with that, Josh. When I started this project, the goal was to "restore" whatever I could instead of "replace". Now, I realize "restore" does not apply to critical mechanical parts but I'm sure you get the point.

Replacing all the nuts and bolts as you say is relatively in expensive. Some of the pulleys etc that are more expensive, I will just have them replated yellow zinc chromate to look as new. I really can fix rounded nuts and bolts and again, the cost to toss them and replace is minor - annoying yes, but still not out of reach.

I'm not cutting any corners. But most of what is in bad condition is do to human hands and human neglect. I was optimistic that the pistons and rings will be fine unless some knuckle head mess with them too

But, as mentioned, I do want to flush the block so I can be sure no FM is inside the oil / coolant passages.

I'm compiling a list of needed parts now and I'm anxious to see what the cost will be. I still think my total out of pocket on this car will be less than $20K and given the interior leather will make up $8K of that, that leaves me quite a bit for mechanicals. If the max I invest is $20k, I'm doing good as the car will be worth much more than my total investment.

And yes, I realize I am working for $2.00 per hour
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