What specifically causes a rod to snap in half?

 

I know for sure that the hardest thing for a rod to do is pull down the piston when it's heading back up (expansion of the rod). Elasticity in metal weakens them while compression (power stroke) isn't so bad.

In Lemans (sp?) terms revving is really what kills them. Usually rod bolts will go and the rod will then break. Power of course also is bad, but revving is much worse

 

well my last motor did this. wasnt making much power so its not that. what do you mean by revving? put a y8 head on my b7 and it lasted a whole 2 minutes before the rod snapped in half. just trying to figure out why it happened.

Uberdata/Crome/TurboEdit Tuner and ECU chipping - Chicagoland and Central Missouri areas

central missouri?? thats where i am. anymore info?

 

Oiling issues would have done it too...

Over reving the motor is what he is talking about, and also bolt failiures..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Adi Raaa &raquo;</TD></TR><TR><TD CLASS="quote">Oiling issues would have done it too...

Over reving the motor is what he is talking about, and also bolt failiures..</TD></TR></TABLE>

what kind of oiling issues? well i didnt over rev it so its not that. and why would i have bolt failure on a greddy turbo kit running stock 5 psi.

 

Wouldnt a very incorrect timing put alot of stress on the motor as well? Say your igniting way to late or way to early?

What rpm did the rod let go on your motor? Under boost?

 

Realistically what happens is the big end of the rod gets so hot that it welds itself to the crank. When that happens, the rod swings around until it hits something hard and then snaps. This can be done at low rpms with no oil available from the oil pump.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mike93eh &raquo;</TD></TR><TR><TD CLASS="quote">

Uberdata/Crome/TurboEdit Tuner and ECU chipping - Chicagoland and Central Missouri areas

central missouri?? thats where i am. anymore info?</TD></TR></TABLE>

Rolla, MO is where I go to school

and now that I read that it broke at low RPM I would say it was oil starvation and earl pretty much said it from there. The incorrect timing statment shouldn't happen because the piston "should" let go way before the rod does if it was heat.....this has happened before on built motors too

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by adseguy &raquo;</TD></TR><TR><TD CLASS="quote">Rolla, MO is where I go to school

and now that I read that it broke at low RPM I would say it was oil starvation and earl pretty much said it from there. The incorrect timing statment shouldn't happen because the piston "should" let go way before the rod does if it was heat.....this has happened before on built motors too</TD></TR></TABLE>

it happened while i was just cruising along at about 3200 rpms.. what caused the oil starvation?

pm'd you..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by adseguy &raquo;</TD></TR><TR><TD CLASS="quote">

Rolla, MO is where I go to school

and now that I read that it broke at low RPM I would say it was oil starvation and earl pretty much said it from there. The incorrect timing statment shouldn't happen because the piston "should" let go way before the rod does if it was heat.....this has happened before on built motors too</TD></TR></TABLE>

So its more likily for the piston to go from incorrect timing than a rod to go? But in a rare case it could?

 

Also if the piston to wall clearance is too tight and the engine overheat, the piston will try to weld itself to the cylinder and then the rod breaks.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Flr Power &raquo;</TD></TR><TR><TD CLASS="quote">Also if the piston to wall clearance is too tight and the engine overheat, the piston will try to weld itself to the cylinder and then the rod breaks.</TD></TR></TABLE>

that didnt happen in my case.

 

How do the bearings look on the rod?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Muckman &raquo;</TD></TR><TR><TD CLASS="quote">How do the bearings look on the rod?</TD></TR></TABLE>

they looked fine to me. but i dont know what bad ones would look like either.

 

You'd know it if you saw it.

 

still wondering what the EXACT cause of this was...