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tips, technology, tools and techniques related to vehicle driveline components

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MGBV8
Carl Floyd
Kingsport, TN
(3232 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Piston Skirt?
Posted by: MGBV8
Date: May 05, 2017 06:41PM

Found this in my lifter valley. No telling how long it has been there. Very light & same curvature as the bore. I believe is is a piece of a piston skirt. I know, I really shouldn't have been revving the piss out of those cast pistons all these years. It always got me home. ;)

Piston skirt 1.jpg
Piston skirt 2.jpg
Piston skirt 3.jpg
Piston skirt 4.jpg


MGBV8
Carl Floyd
Kingsport, TN
(3232 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Piston Skirt?
Posted by: MGBV8
Date: May 05, 2017 06:41PM

Piston skirt5.jpg


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5343 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Piston Skirt?
Posted by: BlownMGB-V8
Date: May 05, 2017 06:46PM

OK it's definitely a piece of piston skirt. But the good news is that it does not break into the oil ring.

Jim


MGBV8
Carl Floyd
Kingsport, TN
(3232 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Piston Skirt?
Posted by: MGBV8
Date: May 05, 2017 06:56PM

Yeah, it appears to be from the bottom of the skirt. Best news is that it got me home from our ChumpCar race at VIR in Danville, VA. Sooooo, maybe Ol' Red has one more V8 Meet before it's new engine time. Hold muh beer.......



Edited 1 time(s). Last edit at 05/05/2017 06:57PM by MGBV8.


mgb260
Jim Nichols
Sequim,WA
(1805 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Piston Skirt?
Posted by: mgb260
Date: May 05, 2017 08:02PM

Carl, One question. How did it get in the lifter valley? It should have went in the pan.


MGBV8
Carl Floyd
Kingsport, TN
(3232 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Piston Skirt?
Posted by: MGBV8
Date: May 05, 2017 08:26PM

Yeah, one would think. I guess the crankshaft knocked it up there. I have never seen anything in the oil. I was considering dropping the pan just to see what else might be in there. Thing is my last trip was over 460 miles round trip. I may replace the head gaskets & forget I ever saw this. I have to get to my 20th V8 Meet in 32 days.


Scott68B
Scott Costanzo
Columbus, Ohio
(495 posts)

Registered:
10/25/2007 11:30AM

Main British Car:
1968 MGB GM 5.3 LS4 V8

authors avatar
Re: Piston Skirt?
Posted by: Scott68B
Date: May 05, 2017 09:24PM

How hard is it to get the pan off?



MGBV8
Carl Floyd
Kingsport, TN
(3232 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Piston Skirt?
Posted by: MGBV8
Date: May 05, 2017 09:43PM

Shouldn't be difficult. Plenty of clearance. Not sure of the need..


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5343 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Piston Skirt?
Posted by: BlownMGB-V8
Date: May 06, 2017 09:31AM

Just at a guess I doubt it's the only piece that came off. The breaks are fresh and clean and you would normally expect a crack to begin at a stress point. Stock pistons commonly had a pair of voids or openings, one on either side of the wrist pin. Those would be a feasible point of origin for a crack because of the unsupported metal below the opening. Meaning that the broken off piece would then have a small unbroken edge on the top side. I suspect you may have such a piece in the oil pan. Not that it would keep the engine from running, and even getting you to the meet and back. And if that is where it started it is again, not in a critical part of the skirt. The angle of the end also suggests there has to be another piece.

Jim


roverman
Art Gertz
Winchester, CA.
(2863 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Piston Skirt?
Posted by: roverman
Date: May 09, 2017 10:39AM

Not to skirt the issue.... is there some additional noise of discontent, from the danger zone ?


DiDueColpi
Fred Key
West coast - Canada
(1218 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
What if the Hokey Pokey really is what it's all about?

authors avatar
Re: Piston Skirt?
Posted by: DiDueColpi
Date: May 09, 2017 12:08PM

You're so close to the problem Carl. It would be a shame not to go just a little further.
I'd pull the pan and replace the pistons.
Run it out for the season and fix it properly next winter.
Or "spin the wheel of tragedy" and see what happens.

Cheers
Fred


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5343 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Piston Skirt?
Posted by: BlownMGB-V8
Date: May 09, 2017 05:47PM

It should be possible to just replace the one broken piston. We did that with Matthew's 383. It came to us with a broken ring land and fresh heads so we just pulled the pan, popped that rod and piston out, and replaced it and he's been running it ever since, with the same rings and bearings.

There should be markings on the piston itself that will help you to identify it. Odds are reasonable that the replacement is still going to be available, but even if not, as long as you find all the pieces you can match a comparable one to the same weight and check top ring position if there is any ridge in the cylinder. If it doesn't rise any higher in the bore or there's no ridge you're good to go.

Jim


pcmenten
Paul Menten

(236 posts)

Registered:
10/08/2009 10:40AM

Main British Car:


Re: Piston Skirt?
Posted by: pcmenten
Date: May 10, 2017 01:46PM

I'm reminded of my best friend in high school who, one-by-one, kept replacing broken pistons in his 289. Eventually, he traded that good running 66 Mustang for a 67 Fairlane GT 390.


MGBV8
Carl Floyd
Kingsport, TN
(3232 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Piston Skirt?
Posted by: MGBV8
Date: May 13, 2017 12:02PM

Thanks, Paul. :)

Cast pistons were not meant for the life they have lived in my MG. Need a short term quick fix. May run it, may go with one piston. Not sure I can swap a whole set of pistons/rings by June with the engine in the car. Not to mention what I will see when I get a look at the rod bearings.

Knew this day was coming. Ol' Red always got me home. May have to park her.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5343 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Piston Skirt?
Posted by: BlownMGB-V8
Date: May 13, 2017 01:19PM

Hope your bearing is good. My first was a hi-po Buick and I ran the snot out of it, figured it'd be OK with 7 grand with that short stroke. Well, apparently not. Cracked a piston skirt, scored the cylinder, and spun the bearing. But you were lucky. First sign I had was loss of power and lots of smoke.

Jim



MGBV8
Carl Floyd
Kingsport, TN
(3232 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Piston Skirt?
Posted by: MGBV8
Date: May 13, 2017 02:01PM

I'll take lucky over good every day of the week, & 2 or 3 times on Sunday! :)



Edited 1 time(s). Last edit at 05/13/2017 02:01PM by MGBV8.


MG four six eight
Bill Jacobson
Wa state
(274 posts)

Registered:
10/23/2007 02:15AM

Main British Car:
73 MGB Buick 215, Eaton/GM supercharger

Re: Piston Skirt?
Posted by: MG four six eight
Date: May 14, 2017 03:23PM

Yeah, back when I swapped out my cast pistons for forged, a couple of the rod bearings were starting to get down to the copper. It never did knock or make noise but apparently they didn't like the 6500 RPM shift points.
Now I never rev it past 6000 and usually not past 5500 and the engine (and my wallet) seem to be a lot happier!

BTW Carl,
If you ever get around to updating to EFI and ditching that dinosaur carburetor;-) you'll find that most EFI systems allow you to set a rev limiter to help prevent self induced damage!
Bill


MGBV8
Carl Floyd
Kingsport, TN
(3232 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Piston Skirt?
Posted by: MGBV8
Date: May 15, 2017 11:22AM

I am champ at self-induced damage, Bill. :)

I don't normally wind it out past 5000 or so on the street. Different story on track days, autox, or slaying the Tail of the Dragon. 16 years of abuse on cast pistons, knew this day way coming ( was hoping for this one last season). Grateful I am not stranded a long way from home.


Scott68B
Scott Costanzo
Columbus, Ohio
(495 posts)

Registered:
10/25/2007 11:30AM

Main British Car:
1968 MGB GM 5.3 LS4 V8

authors avatar
Re: Piston Skirt?
Posted by: Scott68B
Date: May 15, 2017 01:40PM

So have you decided on what you're going to do? Time is getting shorter by the minute! I still have things to complete as well!!


MGBV8
Carl Floyd
Kingsport, TN
(3232 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Piston Skirt?
Posted by: MGBV8
Date: May 15, 2017 03:00PM

Not quite.

I got the driver side head off. About to go pull the pan. Turning the engine by hand, I can't see any skirt below the cylinder on #7, like I can on the rest. If it is #7, then that noise I heard at VIR was only the cracked header on the opposite side. This may be the elusive cold start knocking/piston slap noise, I have been hearing that for years.
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