Bottom end engine failure - at gudgeon pin

PostPost by: BenMcCarthy » Fri Feb 17, 2006 1:32 pm

Hi

I'm looking for any comments/ wisdom on the recent demise of my engine.

Facts known:

1. Engine rebored - full top/bottom rebuild 18 months before.
2. Loud clunk from engine while on the motorway.
3. Pull to halt on hard shoulder steam pouring out of bonnet.
4. Having now had the sump removed at the local garage to do a visual inspection the damage is as follows:
i) con rod to one cylinder only is separated from piston at the gudgeon pin
ii) con rod (now in an 'S' shape) has smashed waterways in the block.
iii) jack shaft/'balance shaft' is snapped in half
iv) cylinder head appears to be fine

Before the engine failure the oil pressure was as usual, water and oil levels as usual before journey started.

Does anyone want to speculate on what might have caused it/ how to avoid this?

Does anyone have advice re my best course of action re bottom end?

Many thanks

Ben
Last edited by BenMcCarthy on Fri Feb 17, 2006 3:43 pm, edited 1 time in total.
BenMcCarthy
First Gear
First Gear
 
Posts: 46
Joined: 20 Oct 2003

PostPost by: steveww » Fri Feb 17, 2006 2:03 pm

Ouch :cry:

Looks like you will need a new block. The original 701 blocks are hard to find but still about if you phone round some of the usual suspects and engine builders. Burton are making new blocks but they are rather expensive. The other option is to go for the tall 711 block which are much easier to get hold of and cheaper, though not original.

Sounds like the gudgeon pin failed or fell out.
User avatar
steveww
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1257
Joined: 18 Sep 2003

PostPost by: john.p.clegg » Fri Feb 17, 2006 4:08 pm

Cylinder head appears fine?-have you taken it off?
Have the valves survived?
Is the short conrod free on the crankpin?
Separated from the piston at the gudgeon pin?Is the rod snapped,the gudgeon pin snapped or the piston broke? (no jokes about my friday night drinking habits thanks)

John :wink:
P.S. whereabouts are you?
User avatar
john.p.clegg
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 4521
Joined: 21 Sep 2003

PostPost by: BenMcCarthy » Fri Feb 17, 2006 4:24 pm

Thanks

Looks like the pin is broken. Possibly the piston connection too.

Not sure if head has been taken off. No obvious problems apparently

I am in South London.
BenMcCarthy
First Gear
First Gear
 
Posts: 46
Joined: 20 Oct 2003

PostPost by: gwnorth68 » Fri Feb 17, 2006 11:27 pm

The big question is whether the little end of the conrod is still happily located by the wrist pin of the piston. If so you've just had a simple fatigue failure of the conrod. Were they 125EC rods or (shudder) the dreaded 116E rods (or something else entirely)? (Surely there aren't any 116E rods left around?)
With luck the piston and small piece of conrod may have just "floated" up to the top of the bore and gently bounced off the head/valves without damaging too much.
Tom Moore
gwnorth68
First Gear
First Gear
 
Posts: 35
Joined: 20 Sep 2003

PostPost by: alaric » Sat Feb 18, 2006 1:29 am

Ouch!

During the rebuild one of the con rods in my engine had to be replaced because it was bent. No idea how this could have happened. It looked fine to the eye, but apparently it could have caused a failure and uneven wear of the bore if put back into the engine. Maybe you had something similar - fatigue related as suggested above - and it caused the gudgeon pin to fail. Maybe in my case engine was worn, and the tolerance of the worn parts caused the bend.

Good luck.

Sean.
alaric
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1062
Joined: 07 Apr 2005

PostPost by: BenMcCarthy » Mon Feb 20, 2006 3:48 pm

Thanks for your replies - to confirm:

the piston is broken just above the gudgeon pin
this caused the pin to separate - the pin itself is still intact
big end of con rod is in place.
small end failure as described above -

faulty/ fatigued piston?
BenMcCarthy
First Gear
First Gear
 
Posts: 46
Joined: 20 Oct 2003

PostPost by: types26/36 » Tue Feb 21, 2006 4:46 am

Ben,
I've seen something like this before when non Twin Cam pistons were fitted, the T.C. pistons should have holes in the oil ring groove for oil drainage, some pistons have slots in the oil ring groove (example: 1500 Ford pistons which can be used in T.C. with some work)
The slotted pistons are "weak!" at this point and should not be used in a T.C.
Just as a matter of interest what type of pistons are in your engine?
Brian.
Brian
64 S2 Roadster
72 Sprint FHC
User avatar
types26/36
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 3402
Joined: 11 Sep 2003

PostPost by: M100 » Tue Feb 21, 2006 10:33 am

BenMcCarthy wrote:
faulty/ fatigued piston?


Quite likely, not missed a downchange and over revved it have you?

Is the piston pin still a good fit in the con rod?

I've seen a case before where a rattling small end was allowed to persist and the piston eventually failed in a similar way to yours.
Martin
72 Sprint DHC
User avatar
M100
Third Gear
Third Gear
 
Posts: 450
Joined: 16 Sep 2003

PostPost by: BenMcCarthy » Mon Mar 06, 2006 10:41 am

Apologies for time to reply -
the pistons were QED pistons (new with the rebuild)

car was cruising along nicely in fourth gear when it happened (no down change or over-revving

not aware of a rattling sound

Thanks

Ben
BenMcCarthy
First Gear
First Gear
 
Posts: 46
Joined: 20 Oct 2003

Total Online:

Users browsing this forum: No registered users and 29 guests