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Piston and cylinder damage

 
Old 02-28-2019, 06:35 PM
  #16  
firemn131
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I don’t know if it means anything, but the Pistons had a number one stamped on them. Does that mean it’s already been bored out once?
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Old 02-28-2019, 06:39 PM
  #17  
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Originally Posted by firemn131 View Post
I don’t know if it means anything, but the Pistons had a number one stamped on them. Does that mean it’s already been bored out once?
No. Cylinder bores and pistons come in "0", "1", and '2" sizes that vary tiny amounts, to enable Porsche to control piston to wall clearance very accurately.
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Old 03-01-2019, 09:03 PM
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Thinking about what the cost of shipping a complete engine (or a short block) around the country, I'd really suggest that you get one oversize piston and have a machinist bore, hone, and prepare that one cylinder. Deck the block, when finished.

Done.
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Old 03-01-2019, 11:02 PM
  #19  
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Yes, that is the way I am leaning depending on what the vendor suggests. I talked to the local Sunnen rep and he pointed me to a shop that is relative local and does this procedure. My machinists (a good friend) has asked me to send him the literature and he may purchase the tool to do this. He has a Sunnen.. However I think the gouge may be too deep. And I would need to sleeve the cylinder.
I was able to wrap my head around the costs to bore it out and new piston. Now I have to try to find the numbers to see what the cost and availability of a sleeve
Iron sleeve?
standard piston?
Pull another piston out to match the weight. My head hurts
i don’t know what I don’t know.
It will all work out though.
I expect that I will be wearing out my welcome on rennlist with all of the questions that I will be asking.

Initial conversation with the vendor was optimistic.
Definately some good people in this community.
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Old 03-01-2019, 11:41 PM
  #20  
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Originally Posted by firemn131 View Post
Yes, that is the way I am leaning depending on what the vendor suggests. I talked to the local Sunnen rep and he pointed me to a shop that is relative local and does this procedure. My machinists (a good friend) has asked me to send him the literature and he may purchase the tool to do this. He has a Sunnen.. However I think the gouge may be too deep. And I would need to sleeve the cylinder.
I was able to wrap my head around the costs to bore it out and new piston. Now I have to try to find the numbers to see what the cost and availability of a sleeve
Iron sleeve?
standard piston?
Pull another piston out to match the weight. My head hurts
i don’t know what I don’t know.
It will all work out though.
I expect that I will be wearing out my welcome on rennlist with all of the questions that I will be asking.

Initial conversation with the vendor was optimistic.
Definately some good people in this community.
Very doubtful that the gouge is too deep for the oversize piston.

If your machinist has a Sunnen, the pieces required bore and finish the cylinder are not that expensive. There are complete instructions in the Porsche Workshop Manual on how to do the procedure. It's not rocket science. There's also a 100 page long technical book, from Kolbenschmidt that tells everything there is to know about sleeves and boring of the block, if you need more information.

Steel sleeves would mean that you'd have to come up with a custom piston for a steel sleeve that weighed the same as a stock piston....not likely.

I now stock Alusil sleeves from Kolbenschmit for these engines. Machine work required. The sleeve is actually "cheaper" than an oversize piston, so that might be an idea. (I'm certain that a "perfect" standard piston would be easy to find.....Mark will have one of those.) I'm putting a sleeve in a GTS block, to save the engine, as we speak. Note that a sleeve would also repair that damage to the top of that one cylinder....

Anything you do to that engine will require complete disassembly (pistons out, crankshaft out, etc.), so pulling another piston out isn't going to be an issue.....
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Old 03-02-2019, 01:58 AM
  #21  
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I personally repaired a block (casting material that never left the block until I removed it ) with some white metal brazing rod. seen here: https://rennlist.com/forums/928-foru...-on-928-a.html

I'll see how it does after I put the engine together, the damage was outside of the fire ring lands so repairing it doesn't require absolute perfection like your damage will.

If your machinist has the correct tools to do the repairs do what Greg says. It'll save you a lot of headache in the future. A fresh alusil sleeve wouldn't be a bad thing
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Old 03-02-2019, 09:04 AM
  #22  
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Originally Posted by firemn131 View Post
Yes, that is the way I am leaning depending on what the vendor suggests. I talked to the local Sunnen rep and he pointed me to a shop that is relative local and does this procedure. My machinists (a good friend) has asked me to send him the literature and he may purchase the tool to do this. He has a Sunnen.. However I think the gouge may be too deep. And I would need to sleeve the cylinder.
I was able to wrap my head around the costs to bore it out and new piston. Now I have to try to find the numbers to see what the cost and availability of a sleeve
Iron sleeve?
standard piston?
Pull another piston out to match the weight. My head hurts
i don’t know what I don’t know.
It will all work out though.
I expect that I will be wearing out my welcome on rennlist with all of the questions that I will be asking.

Initial conversation with the vendor was optimistic.
Definately some good people in this community.
Running a stock Ferro-coated piston in a cast iron sleeve must be possible. I have not tested, anyone having the experience?
Iron-coated piston skirts (Ferrocoat®) guarantee reliable operation when used in aluminium silicon cylinder surfaces (Alusil®).
Åke
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Old 03-02-2019, 11:17 AM
  #23  
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Thanks everyone. You have definitely helped put me at ease.
plan of action is to see how deep the gouge is then if it’s not too deep over bore with the new piston. If it is too deep use the correct liner. I didn’t know they were available in anything other than cast-iron. So that is good news. All of this is if the vendor doesn’t have a replacement block.
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Old 03-02-2019, 05:26 PM
  #24  
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Some interesting reading on the Nikasil insert procedures.

http://www.google.com/url?sa=t&rct=j...vbagIbKRKC2T3t
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Old 03-02-2019, 06:48 PM
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Originally Posted by firemn131 View Post
Some interesting reading on the Nikasil insert procedures.

http://www.google.com/url?sa=t&rct=j...vbagIbKRKC2T3t
Nicasil is a completely different surface treatment than Alusil.

Different pistons, different rings, etc.
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Old 03-02-2019, 06:53 PM
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Originally Posted by Strosek Ultra View Post
Running a stock Ferro-coated piston in a cast iron sleeve must be possible. I have not tested, anyone having the experience?
Iron-coated piston skirts (Ferrocoat®) guarantee reliable operation when used in aluminium silicon cylinder surfaces (Alusil®).
Åke
My machinist thinks that a Ferro-coated piston would be fine in a cast iron sleeve. He claims that most of the older aluminum pistons came coated with iron.

My education tells me that similar metals sliding against each other will gall....

I'm not willing to spend the time to experiment.
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Old 03-02-2019, 07:30 PM
  #27  
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Originally Posted by GregBBRD View Post
My machinist thinks that a Ferro-coated piston would be fine in a cast iron sleeve. He claims that most of the older aluminum pistons came coated with iron.

My education tells me that similar metals sliding against each other will gall....

I'm not willing to spend the time to experiment.
Several cars in the UK running this set up - Westwood cylinder liners and stock pistons. No problems - a 87 S4 5-spd, a GTS racer - BIG GT2 on here, several other GTs, my own GTS 5spd. These engines have run for more than enough hours to prove that the OEM piston coating is compatible with cast ductile iron liners...

Hope this helps,

Alex

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Old 03-02-2019, 10:19 PM
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Originally Posted by Cheburator View Post


Several cars in the UK running this set up - Westwood cylinder liners and stock pistons. No problems - a 87 S4 5-spd, a GTS racer - BIG GT2 on here, several other GTs, my own GTS 5spd. These engines have run for more than enough hours to prove that the OEM piston coating is compatible with cast ductile iron liners...

Hope this helps,

Alex

​​​​​This would be great, of it was a "for certain, long time" approach.

I've seen some very nasty bores and pistons in many 928 engines that ran.

The proof, for me, needs to be absolutely conclusive....everything I build I expect to last as long as it did, originally.

Has anyone taken one of those engines apart to see how the pistone and bores are performing?

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Old 03-03-2019, 11:55 AM
  #29  
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Originally Posted by GregBBRD View Post
​​​​​This would be great, of it was a "for certain, long time" approach.

I've seen some very nasty bores and pistons in many 928 engines that ran.

The proof, for me, needs to be absolutely conclusive....everything I build I expect to last as long as it did, originally.

Has anyone taken one of those engines apart to see how the pistone and bores are performing?
More than happy to shoot a pic or two with my boroscope next time I am near my car. There is no need to take apart the engine to see that there no problems. The 928 will smoke if there were issues with the bores or the pistons’ skirts were galled. As you can imagine the situation would be gradually getting worse. In my mind the proof is absolutely conclusive - the race GTS doesn’t smoke, doesn’t use oil and makes 400-odd BHP, the GTs that I mentioned are daily drivers and so is my GTS.

If you don’t believe me, I am sorry, but the shoe this time is on the other foot. We have put time, effort and money into getting this set up to work. We are happy with the end result. If that’s not enough for you - follow our lead and put your time and money into it. But I ain’t taking a perfectly good engine apart to prove something to someone on the internet...
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Old 03-03-2019, 02:08 PM
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Greg - can you point me to the Kolbenschmit document you reference, I'd like to read it - My google search did not result in any hits. Do you happen to know if they also have Alusil sleeves for Cayenne applications?

Matt
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