sand_man

Okay SoobyDoo fans, I have a bit of a mystery. According to Neil Harvey, one of my connecting rods was bent: out of true by .060 when it was checked for straightness. There was no piston damage, no signs of detonation, no valve impressions on the piston crown, no valve damage, the wrist pins didn't look worn, no broken circ. clips, the crank was fine, and the cylinder bores didn't look funky. I know these aren't Carrillo or Pauter rods, but they aren't made of chocolate either. According to Neil it takes a great deal of force to bend a rod like this...even an OEM one. Now granted I didn't send Neil my old Ps&Cs because I bought brand new ones, so I'm only able to give them a visual inspection...I don't have all those fancy bore gauges. What could cause this? I asked Neil if there was a possibility that the rod was bent when the engine was assembled by Porsche (a defect) and he said that yes it was possible...anything is! You know, built on Friday during Oktoberfest! I don't have a picture yet, but that's been the hold up! Neil has been trying to find a rod that was in the right weight group as the other five...HE FINALLY GOT ONE! When I get the bent one back, I'll snap some pics of it. In the mean time, does anyone have ideas? It would have to be one hell of an explosion in the combustion chamber to bend a rod like this, and then I'd expect to see other damage...

Jeff

Geoffrey

Bent which way? Was it .060" shorter than the 127mm spec?

sand_man

I also asked Neil about the possibility of the rod being bent during shipment from NC to CA. He said that it wasn't possible. That I could stand at one end of his shop and throw the rod as hard as I could against the wall at the other end of his shop and the rod would not sustain damage of this sort.

sand_man

I don't have all the specifics, but the way I was visualizing it was bent in the middle (kinked maybe) in between the small and large end.

PT

You can send your P&C to a machine shop & have them measure for roundness, wear, etc.
If you have a micrometer & feeler gauge, you can probably measure the pistons yourself.

sand_man

I think eventually I will do that. I just wish a knew what caused this. If it were a fueling problem from a faulty and/or leaking injector, I would expect to find VERY obvious damage to other parts.

sand_man

No broken piston rings, either.

sand_man

Also, I'm calling this a mystery, due to the lack of obvious broken parts...with force required to bend a rod wouldn't something have grenaded?

Ron Knowles

I also discovered a bent rod during a rebuild. After some investigation I learned the engine had dropped a valve and had a piston, cylinder and head replaced. I guess the mechanic doing the repairs didn’t see the rod. When I say bent I mean the rod was twisted. The machinist caught it when he was doing the wrist pin bushings. The engine ran for 30k miles like that with no damage to the new cylinder and piston and didn’t make any unusual noises.

sand_man

Interesting! I Have little doubt and so does my machinist, that this is the first time my engine has ever been a part. The engine has 42,000 on it and this is the first rebuild. Neil was shocked that the engine ran like this.

sand_man

I have many of the records for my car, but I'm the fourth owner (the third owner was a car nut and turned cars more often than I change my panties and he only had it for a few months) so I don't have everything. Over the years, I guess it's possible that some work could have been done to one of heads and the bent rod was just missed. Neil, however seems to think that this is the first time these parts have ever been machined.

Chet 930

The cylinder could have filled with fuel at some point previuos and then unloaded. I have seen this a few times where someone doesnt know what thier doing with the CIS system and a cylinder or two will fill with fuel. Then they go and try to push start the car or get it to start somehow meanwhile the filled up cylinder trys to compress the fuel and who knows what gets damaged.

srf506

My guess is it was assembled that way at the factory.

purplehaze.

I have no clue on the cause - but I have some extra rods if you need them.

Glenn

Premier Motorsp

If the turbo fails catastropically enough oil can go into the intake to fill up a combustion chamber.

I saw a racing 944 Turbo do this.

Chris Cervelli
Premier Motorsports