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

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MGBV8
Carl Floyd
Kingsport, TN
(3181 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Piston Skirt?
Posted by: MGBV8
Date: June 04, 2017 11:52AM

Piston is in. Oil pan is back on.


mstemp
Mike Stemp
Calgary, Canada
(176 posts)

Registered:
11/25/2009 07:18AM

Main British Car:
1980 MGB Rover 4.6L

Re: Piston Skirt?
Posted by: mstemp
Date: June 04, 2017 11:56AM

Carl,


Good to hear! Hope all is now back to normal.

Did you have to raise up the engine to get the pan off? Need to change a leaking gasket and want to know if the pan will slide out between the xmember, or if I have remove motor mounts and jack it up.


kstevusa
kelly stevenson
Southern Middle Tennessee
(800 posts)

Registered:
10/25/2007 09:37AM

Main British Car:
2003 Jaguar XK8 Coupe 4.2L DOHC/ VVT / 6sp. AT

authors avatar
Re: Piston Skirt?
Posted by: kstevusa
Date: June 04, 2017 02:10PM

Good News See you in Wytheville for ride to Lewisburg.


MGBV8
Carl Floyd
Kingsport, TN
(3181 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Piston Skirt?
Posted by: MGBV8
Date: June 04, 2017 02:26PM

Doubt I make the Wytheville to Lewisburg Run, Kelly. Study Ken Hiebert's proposals.

I am still staring at a short block, Mike. My car has the stock RB crossmember, so there was plenty of room to remove the oil pan without jacking up the engine.


MGBV8
Carl Floyd
Kingsport, TN
(3181 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Piston Skirt?
Posted by: MGBV8
Date: June 12, 2017 10:25AM

Final update.

Due to time constraints & a well worn engine, I went with Jim Blackwood's suggestion. Down & dirty, fairly quick & easy. Sourced a used OEM standard bore 11:1 piston. Reused the rings that were well seated to the bore & the same rod bearings. New Fel-Pro head gaskets seem to have cured the ridiculously excessive blowby.

I did get the the engine buttoned back up & fired about 30 minutes before pizza time in Lewisburg. I finally arrived at 11pm that evening. No pizza for me.

The next few days confirmed that I did a decent jog putting it all back together, as the West Virginia roads put it to the test with many blasts thru the curves at 5500rpm. :)


302GT
Larry Shimp

(171 posts)

Registered:
11/17/2007 01:13PM

Main British Car:
1968 MGB GT Ford 302 crate engine

Re: Piston Skirt?
Posted by: 302GT
Date: June 14, 2017 11:26AM

This is a very interesting story. I know that your engine has had blow-by problems for many years and now you have found that the piston replacement cured the problem. As I recall the blow-by problem was hard to diagnose because there was no obvious oil smoke from the exhaust. So, did you run a compression or leak down test to try to find the problem? If so, I assume nothing was found, presumably because when the piston was not under load it probably was centered properly in the cylinder.

Was there an obvious cause for the piston failure other than a possible manufacturing defect? I do recall that early Ford 2.3 engines suffered piston skirt failure due to inadequate piston lubrication that was solved by putting an oil squirt hole in the rod. But I have heard of no such problems with the Rover/BOP family of engines.

Anyway, it is great to hear that your repair worked well and I am impressed that the engine suffered no long-term damage.


MGBV8
Carl Floyd
Kingsport, TN
(3181 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Piston Skirt?
Posted by: MGBV8
Date: June 14, 2017 12:44PM

Hi Larry,

The blowby wasn't the piston. It was caused by the bottom row of head bolts canting the heads & leaking compression into the lifter valley. See this thread for the evidence.

[forum.britishv8.org]

I doubt the piston had a defect. It is a cast piston that has endured way too much time living at 6000-7000rpm. Fingers crossed the rest hold up until I can get another engine built.

Piston with the destroyed skirt is on the far right (#7).

http://forum.britishv8.org/file.php?6,file=18752,in_body_attachment=1



Edited 1 time(s). Last edit at 06/14/2017 12:48PM by MGBV8.



302GT
Larry Shimp

(171 posts)

Registered:
11/17/2007 01:13PM

Main British Car:
1968 MGB GT Ford 302 crate engine

Re: Piston Skirt?
Posted by: 302GT
Date: June 14, 2017 01:31PM

Makes sense that the blow-by was the classic head bolt problem.

So, what do you plan for the eventual new engine? I assume it will be a major improvement over the old...


Moderator
Curtis Jacobson
Portland Oregon
(4300 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
Re: Piston Skirt?
Posted by: Moderator
Date: June 14, 2017 02:09PM

Yes. I've been wondering the same thing!


MGBV8
Carl Floyd
Kingsport, TN
(3181 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Piston Skirt?
Posted by: MGBV8
Date: June 14, 2017 02:16PM

Not major & nothing new or even a lot more. I love these little engines.

Strongly leaning toward a Rover 3.9 with new sleeves, a 4.2 crank, & Buick 300 heads. I already have two 3.9 blocks, the 4.2 crank, the 300 heads, a full D&D bellhousing, an Edelbrock intake, & a NASCAR Holley 390 double pumper with mechanical secondaries & 4 corner idle screws. I would be able to reuse my headers, engine mounts, mini starter, & flywheel.

Depending on the bore, displacement about 4.35L. I would be happy with just 225rwhp or so.


MG four six eight
Bill Jacobson
Wa state
(265 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: June 14, 2017 07:42PM

Quote (Was there an obvious cause for the piston failure other than a possible manufacturing defect? I do recall that early Ford 2.3 engines suffered piston skirt failure due to inadequate piston lubrication that was solved by putting an oil squirt hole in the rod. But I have heard of no such problems with the Rover/BOP family of engines.)

Larry brings up a good point.

Some of the Rover/BOP replacement rod bearings do not have the notches cut out for the rod squirter holes.
Back when I built my 10.4 to 1 compression motor, I noticed that the bearings were not notched and thought that is was kind of odd. Thinking that it was simply a matter of an updated part, I installed them as is.

Then 19,000 miles latter when I decided to supercharged engine, I tore it down and found excessive scuffing on all 8 pistons and cylinder walls. Due to the excessive scoring on the pistons/cylinder walls with fairly low mileage, I determined that the squirter holes do indeed need to be functional in order for the piston/cylinder wall to receive proper lubrication.

When building the supercharged engine with cast 8.6 to 1 pistons, I notched the ends of rod bearings with a Dremmel (spelling) tool. I ran the 8.6 pistons for a few years, before I decided to tear it down again and switch to forged pistons so that I could run more boost safely.
When I tore it down to install the forged pistons, there was no piston/cylinder wall scoring found when using the modified/notched rod bearings. Needless to say I notched the rod bearings when building the forged piston motor and will continue to do so on any Rover/BOP rod bearing that isn't already notched!

Bill



Edited 3 time(s). Last edit at 06/14/2017 07:46PM by MG four six eight.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5284 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: June 15, 2017 10:05AM

Hey Carl! At least you had ONE piston that wasn't leaking blowby into the lifter valley!

Jim


MGBV8
Carl Floyd
Kingsport, TN
(3181 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Piston Skirt?
Posted by: MGBV8
Date: June 15, 2017 11:31AM

I was under the gun to get it back together in time for the V8 Meet. I really don't remember a notch in the rod bearing for the oil hole.

I am just tickled that it held together with the abuse I subjected it to in West Virginia! :)


MG four six eight
Bill Jacobson
Wa state
(265 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: July 01, 2017 12:20PM

Glad you were able to get it back together Carl! Regarding the oil spray hole in the bearings, it's something to check for on your next build.

For those who don't know the original rod bearings had notches that allowed oil to be sprayed up on the piston, cylinder wall and wrist pin, via a notch in the rod/cap. This lubes the piston/related parts and just as importantly cools the bottom of the piston with oil spray.
Some of the replacement rod bearings do not have the notch which effectively closes off the lube port in the rod. Notching the replacement bearings is fairly simple to do using a dremmel tool though. The main thing is to go slow and slightly bevel the edge of the notch so that there are no rough edges on the bearing surface.

Bill


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5284 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: July 01, 2017 05:10PM

Also sprays oil on the cam lobes.

Jim



Dan B
Dan Blackwood
South Charleston, WV
(890 posts)

Registered:
11/06/2007 01:55PM

Main British Car:
1966 TR4A, 1980 TR7 Multiport EFI MegaSquirt on the TR4A. Lexus V8 pl

authors avatar
Re: Piston Skirt?
Posted by: Dan B
Date: July 01, 2017 06:25PM



Scott68B
Scott Costanzo
Columbus, Ohio
(489 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: July 01, 2017 10:39PM

😊 Every now and then you come up with a good one Dan!
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