Rough cylinder walls, What can be the cause? |
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Rough cylinder walls, What can be the cause? |
HansJan |
Oct 19 2016, 09:28 PM
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#1
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Member Group: Members Posts: 395 Joined: 5-April 16 From: Sugar Land TX Member No.: 19,860 Region Association: Southwest Region |
Hello,
Today the shop had taken the engine out of the car, just to replace the very stiff valve springs. When the heads came off we noticed that there are rough areas on the cylinder walls. Not everywhere, but at least two areas per cylinder. FYI: Cylinders are 103.8 mm (by AA). Pistons are also by AA. Markings on cam: CWC Valves Intake: 44.35 mm Valve Exhaust: 38 mm My question to the brain-trust is: What could be the cause for the rough areas? Some back ground info: This car supposed to have "Nickies" Cylinders and JE-Pistons. Obviously the (Craigslist) seller and I are no friends. After receiving it, I drove the car for less then 10 minutes before the car caught on fire. |
wndsrfr |
Oct 20 2016, 05:31 AM
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#2
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Senior Member Group: Members Posts: 1,430 Joined: 30-April 09 From: Rescue, Virginia Member No.: 10,318 Region Association: MidAtlantic Region |
Hello, Today the shop had taken the engine out of the car, just to replace the very stiff valve springs. When the heads came off we noticed that there are rough areas on the cylinder walls. Not everywhere, but at least two areas per cylinder. FYI: Cylinders are 103.8 mm (by AA). Pistons are also by AA. Markings on cam: CWC Valves Intake: 44.35 mm Valve Exhaust: 38 mm My question to the brain-trust is: What could be the cause for the rough areas? Some back ground info: This car supposed to have "Nickies" Cylinders and JE-Pistons. Obviously the (Craigslist) seller and I are no friends. After receiving it, I drove the car for less then 10 minutes before the car caught on fire. Hmm...those look like stains from the wrist pin side of the piston....metal looks ok, can see honing scratches across the stain. |
N_Jay |
Oct 20 2016, 07:44 AM
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#3
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Member Group: Members Posts: 283 Joined: 2-March 16 From: Chicago NW Burbs Member No.: 19,720 Region Association: None |
Are the marks on the front and back or top and bottom?
Can you feel them at all? |
injunmort |
Oct 20 2016, 12:43 PM
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#4
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Senior Member Group: Members Posts: 1,024 Joined: 12-April 10 From: sugarloaf ny Member No.: 11,604 Region Association: North East States |
looks like some one forgot the wrist pin keepers. i have seen that before. it does not end well.
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McMark |
Oct 20 2016, 12:59 PM
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#5
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914 Freak! Group: Retired Admin Posts: 20,179 Joined: 13-March 03 From: Grand Rapids, MI Member No.: 419 Region Association: None |
I can see from the cylinder fins that those marks are on the top or bottom. I'm guessing the top since the bottom usually has oil leaking out of it.
My WAG (wild ass guess) is that it's something to do with the rings chattering or piston rock. 104 pistons aren't really reliable. Did you measure the stroke? An engine that uses 104s has to have a lot of other engine components upgraded to do right. If the rest of the components aren't right things like piston speed and rod ratio can cause problems. Building a 104 engine right will cost as much or more than buying a 911 engine, but won't be nearly as reliable or powerful. Check over the rest of the components, but if I were you I would plan on installing new 96mm pistons and cylinders. |
worn |
Oct 20 2016, 01:12 PM
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#6
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can't remember Group: Members Posts: 3,156 Joined: 3-June 11 From: Madison, WI Member No.: 13,152 Region Association: Upper MidWest |
I can see from the cylinder fins that those marks are on the top or bottom. I'm guessing the top since the bottom usually has oil leaking out of it. My WAG (wild ass guess) is that it's something to do with the rings chattering or piston rock. 104 pistons aren't really reliable. Did you measure the stroke? An engine that uses 104s has to have a lot of other engine components upgraded to do right. If the rest of the components aren't right things like piston speed and rod ratio can cause problems. Building a 104 engine right will cost as much or more than buying a 911 engine, but won't be nearly as reliable or powerful. Check over the rest of the components, but if I were you I would plan on installing new 96mm pistons and cylinders. I cannot see piston velocity changing since that is RPM given constant rod length. It is gonna be more over square fear sure. What else needs to be done to make things work? Love to learn from you guys. |
injunmort |
Oct 20 2016, 04:16 PM
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#7
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Senior Member Group: Members Posts: 1,024 Joined: 12-April 10 From: sugarloaf ny Member No.: 11,604 Region Association: North East States |
piston speed changes dramatically at tdc and btdc. it goes from max velocity to stop.
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porschetub |
Oct 21 2016, 01:37 AM
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#8
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Advanced Member Group: Members Posts: 4,701 Joined: 25-July 15 From: New Zealand Member No.: 18,995 Region Association: None |
I can see from the cylinder fins that those marks are on the top or bottom. I'm guessing the top since the bottom usually has oil leaking out of it. My WAG (wild ass guess) is that it's something to do with the rings chattering or piston rock. 104 pistons aren't really reliable. Did you measure the stroke? An engine that uses 104s has to have a lot of other engine components upgraded to do right. If the rest of the components aren't right things like piston speed and rod ratio can cause problems. Building a 104 engine right will cost as much or more than buying a 911 engine, but won't be nearly as reliable or powerful. Check over the rest of the components, but if I were you I would plan on installing new 96mm pistons and cylinders. (IMG:style_emoticons/default/agree.gif) huge cylinders that go out of round when hot and out of shape,the heads get less supportive @ register size,see the hone marks still there but think not much is staying round ,AA pistons ????? some don't get good press. I tend to remember the thin T1 no bore kits from a long way back,same issue for another reason,just saying ??? |
HansJan |
Oct 21 2016, 06:29 AM
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#9
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Member Group: Members Posts: 395 Joined: 5-April 16 From: Sugar Land TX Member No.: 19,860 Region Association: Southwest Region |
QUOTE (IMG:style_emoticons/default/agree.gif) huge cylinders that go out of round when hot and out of shape,the heads get less supportive @ register size,see the hone marks still there but think not much is staying round ,AA pistons ????? some don't get good press. I tend to remember the thin T1 no bore kits from a long way back,same issue for another reason,just saying ??? Thanks for your input. What is is T1? |
76-914 |
Oct 21 2016, 07:35 AM
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#10
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Repeat Offender & Resident Subaru Antagonist Group: Members Posts: 13,504 Joined: 23-January 09 From: Temecula, CA Member No.: 9,964 Region Association: Southern California |
QUOTE (IMG:style_emoticons/default/agree.gif) huge cylinders that go out of round when hot and out of shape,the heads get less supportive @ register size,see the hone marks still there but think not much is staying round ,AA pistons ????? some don't get good press. I tend to remember the thin T1 no bore kits from a long way back,same issue for another reason,just saying ??? Thanks for your input. What is is T1? Type 1 = VW and some bus |
worn |
Oct 21 2016, 08:16 AM
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#11
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can't remember Group: Members Posts: 3,156 Joined: 3-June 11 From: Madison, WI Member No.: 13,152 Region Association: Upper MidWest |
piston speed changes dramatically at tdc and btdc. it goes from max velocity to stop. That isn't exactly an explanation. What I was suggesting is that given the same crank and rods, how does the diameter of the piston alter piston acceleration and speed? At a given RPM, I would have expected the larger pistons to move in the same path as the smaller ones. Now they will be more over square and perhaps be less stable with a short skirt. Also, it does look like marls from the wrist pin. How does the diameter play into that? Thanks |
McMark |
Oct 21 2016, 08:42 AM
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#12
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914 Freak! Group: Retired Admin Posts: 20,179 Joined: 13-March 03 From: Grand Rapids, MI Member No.: 419 Region Association: None |
Yeah, I wrote that poorly. What I had in mind is that this engine may have stock rods with an increased stroke.
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injunmort |
Oct 21 2016, 11:59 AM
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#13
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Senior Member Group: Members Posts: 1,024 Joined: 12-April 10 From: sugarloaf ny Member No.: 11,604 Region Association: North East States |
my apologies worn, i misunderstood the question. i dont think diameter would cause these marks, i have seen this in motorcycle engines when a wrist pin clip is not installed. when the engine gets to operating temp the wrist pin will bounce in and out of the piston contacting the cylinder wall. it will mangle the cylinder if left unattended.
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HansJan |
Oct 22 2016, 10:46 AM
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#14
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Member Group: Members Posts: 395 Joined: 5-April 16 From: Sugar Land TX Member No.: 19,860 Region Association: Southwest Region |
my apologies worn, i misunderstood the question. i dont think diameter would cause these marks, i have seen this in motorcycle engines when a wrist pin clip is not installed. when the engine gets to operating temp the wrist pin will bounce in and out of the piston contacting the cylinder wall. it will mangle the cylinder if left unattended. Oh my GOD. That would be a disaster. Will call the shop first thing on Monday to check. Thanks guys. |
cwpeden |
Oct 22 2016, 11:16 AM
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#15
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Great White North, huh? Group: Members Posts: 916 Joined: 20-August 06 From: Victoria BC Member No.: 6,693 Region Association: Canada |
From a machinists point of view, those look like resonance rings.
As the cylinders were machined they were ringing and that pattern can translate all through finishing. |
cwpeden |
Oct 22 2016, 11:18 AM
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#16
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Great White North, huh? Group: Members Posts: 916 Joined: 20-August 06 From: Victoria BC Member No.: 6,693 Region Association: Canada |
my apologies worn, i misunderstood the question. i dont think diameter would cause these marks, i have seen this in motorcycle engines when a wrist pin clip is not installed. when the engine gets to operating temp the wrist pin will bounce in and out of the piston contacting the cylinder wall. it will mangle the cylinder if left unattended. Oh my GOD. That would be a disaster. Will call the shop first thing on Monday to check. Thanks guys. Highly unlikely as they are 90 degrees to the wrist pins |
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