Broken Piston Bits in Sump

356 Porsche-related discussions and questions.
Message
Author
User avatar
Dan Mazur
356 Fan
Posts: 205
Joined: Wed Mar 26, 2008 12:50 am

Broken Piston Bits in Sump

#1 Post by Dan Mazur »

HI Folks,
I have a 912 engine that I acquired used a decade ago and am just getting around to starting it up, or so was the plan.
The PO stated at the time it had been "rebuilt" with a $400 big bore kit.
When I drained the oil from the deep sump, 1/2" size pieces of a piston feel out along with bits of an oil control ring. :shock: Seems like the skirt got chunked off.

My question for the group is, what could cause this? :?

Of note, it seems like it is from the #1 piston because I can hear it crunch a little when turning the engine over by hand. The engine does turn freely.
Also, there is NO valve clearance on that head, and the rocker adjusters are all the way backed out. The other side looks fine.

Well, the bright side is I didn't pay much for this engine back then, and I suppose I got what I paid for. Would have been nice if the seller told me about this at the time, but I guess for some people that too much to ask for.

Thanks in advance for your thoughts.
Dan
"I never leave Ann Arbor. The real world is too hard to face."

User avatar
David Jones
Classifieds Moderator
Posts: 7323
Joined: Tue Mar 25, 2008 6:32 pm
Tag: I wish I knew as much as I think I know.
Location: Kentucky

Re: Broken Piston Bits in Sump

#2 Post by David Jones »

Dan, you have no option but to tear it down and see what broke and that should tell you what went wrong. No good guessing on this one because of the multitude of possible reasons.
If I had known I would live this long I would have pushed the envelope a little harder.
Cymru am byth
David Jones #9715

WilliamVaughan
356 Fan
Posts: 446
Joined: Fri Dec 03, 2010 7:42 am

Re: Broken Piston Bits in Sump

#3 Post by WilliamVaughan »

The Maestro used to have his wife take documentation photos of the chunks for his books. He termed one of the failure modes, "the ring eating monster". Ron LaDow has explaned why some of the chunks get blasted off. Please consider taking and posting some photos of the parts and pieces so that we may learn from other's mistakes.

Dick Weiss
356 Fan
Posts: 4183
Joined: Sun Apr 20, 2008 12:54 am

Re: Broken Piston Bits in Sump

#4 Post by Dick Weiss »

Dan,

I suggest a full teardown as you'll need a full cleanout of all oil passages in the case and inspect everything from the crank out.
Obviously, the P/Cs will need replacement, but the cylinder heads will need to be checked per specs if they've been fly-cut excessively and not checked for exhaust valve clearance to the piston's top reversal location.
Having the valve adjusting screws fully out suggests the heads (and/or the rocker stands) weren't spaced outward enough to get the piston-to-deck clearance.

The adjusting screws need to be 1-1/2turns inward from full outward after the valve clearances are set.
If not, oil won't flow thru to lube the rockers and shafts!

Dick

Norm Miller
356 Fan
Posts: 2506
Joined: Thu Mar 27, 2008 9:14 am
Tag: Official curmudgeon
Location: Ft Collins CO

Re: Broken Piston Bits in Sump

#5 Post by Norm Miller »

The flotsam in the "deep sump" could belong to the previous piston/s before the big bore rebuild.
With a good light look up into the case or turn it on it's back, rotate the crank and observe the skirts of the pistons.
Is the case clear of crap and contamination?
I have assumed it has a bolt on deep sump according to your post, otherwise, disregard.

#3294
 

User avatar
Wes Bender
356 Fan
Posts: 4861
Joined: Wed Aug 27, 2008 10:54 am
Location: Somewhere in the Gadsden Purchase, USA

Re: Broken Piston Bits in Sump

#6 Post by Wes Bender »

My guess is that, during the rebuild, a piston with a longer skirt was used. On start-up, the crank took a bite or two out of the piston skirt and resulted in a drastic reduction in engine price for you......

Now you have the chance to rebuild it right.

(Edited after picture of pistons are shown in a later post: Skirts on pistons are not too long, eliminating them as the problem.) Now looking more like a piece of debris caught between the crankshaft and piston skirt while engine was running. Piston skirts don't just break off by themselves.

You still have the chance to rebuild it right.......
Last edited by Wes Bender on Fri Feb 15, 2019 2:51 pm, edited 1 time in total.
Some days it's just not worth chewing through the restraints.....

User avatar
Ron LaDow
356 Fan
Posts: 8092
Joined: Wed Mar 26, 2008 11:45 am
Location: San Francisco

Re: Broken Piston Bits in Sump

#7 Post by Ron LaDow »

I would avoid turning the crank; there is likely swarf spread throughout the engine and some of it is likely embedded in the bearings. Every time you rotate the crank, you're adding scratches to the journals.
Ron LaDow
www.precisionmatters.biz

Dick Weiss
356 Fan
Posts: 4183
Joined: Sun Apr 20, 2008 12:54 am

Re: Broken Piston Bits in Sump

#8 Post by Dick Weiss »

If a 1720 P/C kit was installed, the pistons would have shorter skirts to clear the crankshaft counterweights during rotation.

User avatar
Dan Mazur
356 Fan
Posts: 205
Joined: Wed Mar 26, 2008 12:50 am

Re: Broken Piston Bits in Sump

#9 Post by Dan Mazur »

Great insight and advise. Thanks so much to all.
Here are a few pics of the bits I fetched out of the deep sump.

First picture from left to right my guesses are: oil control ring, piston skirt, not sure what the broken circular black item is from on the far right..anyone?
Last picture of the blue sealant is just for grins and represents of the level of professionalism that apparantly went into this engine.

I also noticed that it has aluminum pushrods (912 version) and cast iron jugs. My reading here seems to indicate this is not a good idea and I should switch to steel pushrods.

Ill break the engine down this weekend and post an update.
Thanks again
Dan
Attachments
912 Piston Bits 1.JPG
912 Piston Bits 1.JPG (1.97 MiB) Viewed 1700 times
Unknow Bit.JPG
Unknow Bit.JPG (1.94 MiB) Viewed 1700 times
Head Sealant.JPG
Head Sealant.JPG (1.83 MiB) Viewed 1700 times
"I never leave Ann Arbor. The real world is too hard to face."

User avatar
Craig Richter
356 Fan
Posts: 1305
Joined: Thu Dec 15, 2011 9:01 pm
Location: San Miguel de Allende/Traunkirchen

Re: Broken Piston Bits in Sump

#10 Post by Craig Richter »

Dan,
912 pushrods are steel (albeit a type of stainless steel) not aluminum, and along with your cast iron cylinders (properly bored for some nice 86mm Shasta pistons of course) are a perfect start for a good street motor. It's that black semi-circlular piece of smeg that got my attention. What the heck is that? And that sealant under the rocker stands is enough reason you need a complete rebuild.
 

User avatar
Ron LaDow
356 Fan
Posts: 8092
Joined: Wed Mar 26, 2008 11:45 am
Location: San Francisco

Re: Broken Piston Bits in Sump

#11 Post by Ron LaDow »

The scrap you've found indicates the engine was not long in use; for instance, there is no oxidized oil on the piston skirt pieces. It looks like this was not a 'use' failure, but an 'assembly' failure.
But I'm really having a hard time imagining an engine assembly process which was so (x)ed-up as to cause one piston to simply disassemble itself and end up in the sump.
My guess is this (and it is a guess only): The assembly got to fitting the cylinders to the pistons and one would simply not go. Frustration, frustration and finally a hammer. A BIG one.
Please do keep us informed.
Added by edit: What is the material in the black semi-circle?
Ron LaDow
www.precisionmatters.biz

Norm Miller
356 Fan
Posts: 2506
Joined: Thu Mar 27, 2008 9:14 am
Tag: Official curmudgeon
Location: Ft Collins CO

Re: Broken Piston Bits in Sump

#12 Post by Norm Miller »

What's the puss oozing around the head bolts?

The swarf you dug out of the deep sump doesn't resemble a big bore.
I'm still betting they didn't clean the deep sump after the explosion and if so, you are lucky.

Might as well pull the heads anyway and get rid of the blue stuff which is designed the perfectly fit into oil gallies.
 

User avatar
Al Zim
356 Fan
Posts: 4309
Joined: Thu Mar 27, 2008 12:37 pm
Location: FT.WORTH/DALLAS TEXAS
Contact:

Re: Broken Piston Bits in Sump

#13 Post by Al Zim »

Everything that has been discussed is irrelevant to your situation. You are not the only one that has purchased 356 parts and been swindled. Take everything apart clean everything and then take it to a reputable shop that can measure the parts and they can tell you what needs to be done. OUCH! al zim
www.allzim.com 
356 Parts and Services
www.facebook.com/ZimsAuto/
www.instagram.com/zims_autotechnik/

User avatar
Wes Bender
356 Fan
Posts: 4861
Joined: Wed Aug 27, 2008 10:54 am
Location: Somewhere in the Gadsden Purchase, USA

Re: Broken Piston Bits in Sump

#14 Post by Wes Bender »

Disregard the previous "irrelevant" post. You CAN rebuild your own engine. It is only natural that repair shops don't want you to do it yourself, but you can do just as good a job as those shops can. Bear in mind that they have to operate at a profit, so the work has to be done either within specific man-hour limits or else on a time and materials basis. You, on the other hand, can take your time and do it correctly without it affecting your bottom line.

I'm not saying shops don't do a good job. Most of them do. However, with the right tools and books, you can do just as good a job and get the satisfaction of doing it yourself.

Just my $.02. Flame suit on.......
Some days it's just not worth chewing through the restraints.....

User avatar
Craig Richter
356 Fan
Posts: 1305
Joined: Thu Dec 15, 2011 9:01 pm
Location: San Miguel de Allende/Traunkirchen

Re: Broken Piston Bits in Sump

#15 Post by Craig Richter »

Wes,
Fire extinguisher here.
++1 on your 2 cents.
 

Post Reply