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beancounter
 
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quick piston replacement job ---> oil pooled in cylinder?

Here's the skinny...pelican Vin-Barrett's '83 SC started blowing major smoke last week. Lots of oil in the tailpipe. Spark plugs were pulled and found that #6 was very oily. Diagnosis: lunched ring(s), possibly lunched piston and cylinder on #6.

The plan: quick engine drop, pull the heads on the right bank, replace #6 piston and cylinder with used parts from the spares collection, plug engine back in and continue driving like its stolen.

engine out:


vintage Oldsmobile workbench:


heads off, #6 jug removed:


what have we here?


#6 piston. Stone cold busted:


Unsurprisingly, there was oil pooled in #6 cylinder. What is puzzling is that we also found oil pooled in #4. #5 was clean. Note that the #4 sparkplug was clean, and it did not appear that oil was being burned there. Question is, how did the oil get in there? Why is #5 dry but #4 is not. The oil in #4 led us to believe that it might also have a ring or piston problem so we pulled the jug. The rings and piston were fine, so the question remains as to origins of the oil in #4. Anyone have any ideas or similar experience?

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Current: 1983 911 GT4 Race Car / 1999 Spec Miata / 2000 MB SL500 / 1998 MB E300TD / 1998 BMW R1100RT / 2016 KTM Duke 690
Past: 2009 997 Turbo Cab / 1979 930
Old 07-10-2010, 06:38 PM
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Without seeing everything for myself, I can only offer an educated guess, but with that piston destroyed by detonation, lots of oil gets pumped into the airbox and the resulting crankcase pressure will push oil into most of the other cylinders.

I would certainly address the root cause of the detonation otherwise you are likely to have an "encore performance".
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Old 07-10-2010, 09:27 PM
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beancounter
 
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Thanks for your input Steve. It was also my guess that the crankcase pressure pushing oil through the intake was the reason for the wet #4 jug. The only reason we had trouble with this theory is that #5 looks perfectly dry and normal. I suppose one could assume that when the engine was stopped and allowed to sit, that the #4 intake valve was open and #5 intake was closed, but wouldn't you expect to find oil pooled in the #5 intake port?
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Old 07-11-2010, 05:11 AM
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Please tell me you are NOT going to work over the engine with a cigarette in your mouth!
The ash from that thing is metallic and will get into the bearings and undo all your hard work.
If you ever get a chance to go to a professional engine builder and watch a race engine being assembled by technicians wearing all white clothing and masks over their mouths, you will get the idea that dirt is the enemy.
Good luck on the repair.
Bob
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Old 07-11-2010, 09:01 AM
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Good luck and hope all goes well. Thanks for introducing me to my first fun run. My son and I enjoyed it! Hope to see Vinny next time.


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Old 07-11-2010, 01:44 PM
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Wil84911, when were you guys in Bloomsbury?
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1969 911T Coupe
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Last edited by dafischer; 07-11-2010 at 02:05 PM..
Old 07-11-2010, 02:03 PM
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Dave, this past monday 7/5 around 8AM. I was tagging along so not sure of the route.
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99 C4 - (let's try this once more)
07 Cayman S - sold 11/17 (not the same)
84 Carrera - sold 3/16 (geez what have I done!)
Old 07-11-2010, 02:45 PM
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Quote:
Originally Posted by Steve@Rennsport View Post
Without seeing everything for myself, I can only offer an educated guess, but with that piston destroyed by detonation, lots of oil gets pumped into the airbox and the resulting crankcase pressure will push oil into most of the other cylinders.
I would +1 that but also agree that intakes would be pretty oily too. Especially with taking it down so soon after the problem.

I'm assuming you haven't pulled those other pistons yet (and would be hard pressed to do it if avoidable) and would also assume that if those pistons had some kind of unseen damage you'd see scoring on the walls. I would check tolerances (the best I could) on the bad piston. Looks like all of the rings were somewhat destroyed so checking ring gap is probably out. Check the piston good though and if it appears (other than the obvious damage) to be well worn then you can place bets that you have other cylinders with the same wear. i.e. . . could the pooling just be P/C wear??

I'm sure you're looking for the reason too. And if it happens again, take his keys.
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Old 07-11-2010, 03:00 PM
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Quote:
Originally Posted by HawgRyder View Post
Please tell me you are NOT going to work over the engine with a cigarette in your mouth!
Its called a cigarette "break" and the engine wasn't open in that photo.

Quote:
Originally Posted by HawgRyder View Post
The ash from that thing is metallic and will get into the bearings and undo all your hard work.
You mean like the metal in the broken ring and piston pieces that are already sitting in the sump? As stated Bob, this is a quick and dirty repair job to get this car back on the road ASAP so a sterile, dust free clean room white lab coat assembly isn't in the cards this time. Vin doesn't want to do a rebuild on this engine, just wants to keep driving the car. He wants to upgrade to a 3.6 engine sometime, that is if I don't convince him to turbo it instead

Quote:
Originally Posted by WIL84911 View Post
Good luck and hope all goes well. Thanks for introducing me to my first fun run. My son and I enjoyed it! Hope to see Vinny next time.
Welcome Will...nice meeting you and your son and glad you had fun. The reason for the quick repair is to get Vin back on the road so he can come along on the next run soon.

Quote:
Originally Posted by dafischer View Post
Wil84911, when were you guys in Bloomsbury?
I used to live down the road from there on Rt 627...we went across the Riegelsville Bridge and then down to New Hope on Rt32/River Road.

Quote:
Originally Posted by d.a.autry View Post
I'm sure you're looking for the reason too. And if it happens again, take his keys.
The reason for the failure is either detonation (timing set advanced + very hot weather + Vinny likes to drive the car hard) or perhaps ring "flutter" (these were used pistons & cylinders that had been re-ringed approx 3 years ago). We checked #4 because of the oil in there and found it looking fine. #5 shows no evidence of problems and we left it alone. The left bank is not even being opened up this time.

Take his keys? Whatever for? Drive 'em hard, break 'em or wear 'em out, fix 'em up, then repeat. I met Vinny because he responded to my plea for assistance on my first engine drop. He helped me at several stages of my DIY engine rebuild and then helped me plug it back in to the car. He's a true Pelican.
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Old 07-11-2010, 05:48 PM
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I used to live down the road from there on Rt 627...we went across the Riegelsville Bridge and then down to New Hope on Rt32/River Road.
I live off Rt 614 on the east side of the mountain, and there really are some great roads out here in Bucks, Hunterdon, and Warren counties. River Rd. to No Hope is a nice run, if you don't get stuck behind some rubbernecking Touristas. Let me know if you're going to be out this way sometime, and maybe I could join up with your group, if you don't mind a longhood tagging along. I might be able to get another friend in his 930 along as well.
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Old 07-11-2010, 06:35 PM
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River Rd. to No Hope is a nice run, if you don't get stuck behind some rubbernecking Touristas.
Ha...no doubt. This is why we gathered at 630am...to avoid traffic. We had fairly open roads most of the morning.

Quote:
Originally Posted by dafischer View Post
Let me know if you're going to be out this way sometime, and maybe I could join up with your group, if you don't mind a longhood tagging along. I might be able to get another friend in his 930 along as well.
PM'ing you my contact info. Good chance we'll be back...I will for sure as my father still lives out there. The more the merrier and longhoods are cool.
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Old 07-11-2010, 07:20 PM
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That first picture is one of the best I've seen here in a long time! The composition tells the story. good job.
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Old 07-11-2010, 08:09 PM
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Was there regular gas in the tank and not premium ?
Old 07-12-2010, 01:47 AM
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So did you guys finish up and get her back on the road on Sunday?

I'm sorry I didn't make it over to lend a hand. I finally got to ride the wheels off my bike this weekend after last weekend's fun with head gaskets!
Old 07-12-2010, 11:40 AM
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Quote:
Originally Posted by HawgRyder View Post
Please tell me you are NOT going to work over the engine with a cigarette in your mouth!
The ash from that thing is metallic and will get into the bearings and undo all your hard work.
If you ever get a chance to go to a professional engine builder and watch a race engine being assembled by technicians wearing all white clothing and masks over their mouths, you will get the idea that dirt is the enemy.
Good luck on the repair.
Bob
Not to worry....
I took off my work clothes for the picture, and a smoke...

This is me in my work gear when working on cars....



Thanks for the advice

-vin
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Old 07-12-2010, 07:37 PM
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Quote:
Originally Posted by Ed_ View Post
So did you guys finish up and get her back on the road on Sunday?

I'm sorry I didn't make it over to lend a hand. I finally got to ride the wheels off my bike this weekend after last weekend's fun with head gaskets!
Hey Ed

Sorry we missed you..
The motor is all back together, probably stick it in Friday after work
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Old 07-12-2010, 07:43 PM
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Cool!

So, what was the cause of the detonation?

Sorry, I won't be around on Friday evening, either. I'm going to Myrtle Beach. Good luck, man.

Quote:
Originally Posted by Vin-barrett View Post
Hey Ed

Sorry we missed you..
The motor is all back together, probably stick it in Friday after work


Last edited by Ed_; 07-13-2010 at 09:54 AM..
Old 07-13-2010, 09:26 AM
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