• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Destroyed Pistons

Share this page

aeronca65t

aeronca65t

Great Pumpkin
Offline
This piston (#1) came out of my 1500 Spridget in early '04 (while I was rebuilding it). I was surpised to see this much damage since the car was running OK and was not "missing" on this cylinder. Prior to this dissassembly, it had just finished decently in a 1 hour race at Summit Point (WV).
A portion of the upper land failed (I guess) allowing the upper piston ring to break into a bunch of pieces. I found some pieces of the ring in the sump. The square-ish marks on top of the piston were caused by pieces of ring hammering into the top. The head in #1 area looked like it was bead-blasted, but no other damage.
This was a 7.6:1 low-compression piston. The engine has been rebored (+.020) and I've put in 9:1 flat-top pistons instead. New cam, ARP hardware, 3-angle valve job and a bunch of other stuff too. Other than a minor bit of vapor lock, it runs good now!

1500_piston.jpg
 
Interesting paperweight you have there Nial. Isn't it amazing how these little engines can be hurting inside but keep on giving their all? I know that racing will test the mettle of any engine so good luck with the rebuilt unit.
thumbsup.gif
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by aeronca65t:
... I found some pieces of the ring in the sump...<hr></blockquote>

How do you suppose pieces made it to the sump? Is there a hole in the piston?
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by coldplugs:


How do you suppose pieces made it to the sump? Is there a hole in the piston?<hr></blockquote>

A compete mystery to me too, John.
There is no hole in the piston, other than the expansion slots that are below the oil ring (which was still intact). The damaged area in the piston was not "broken through". Cylinder wall wasn't terribly damaged either.
Fourth Dimension?
 
The solution is easy: The ring pieces got into the sump through the valve guides! (Is this realy any less plausable than they just "slipped" down the skirt and by the oil ring??)

That's amazing...

/ubbthreads/images/graemlins/laugh.gif /ubbthreads/images/graemlins/confused.gif /ubbthreads/images/graemlins/laugh.gif /ubbthreads/images/graemlins/confused.gif
 
Through the guides! Of course! Why didn't I think of that?

Normally, my hypothesis would be that they were there from a previous mishap, but I suspect that Nial knows the engine pretty well so that's not likely.

[ I once dropped the thin retainer from the master link of an Alfa camshaft chain into the engine & decided that it was safe to just leave it there. A few months later we pulled the pan and there were three of them in the sump. ]
 
Back
Top