I was quite surprise when I read this thread over at my350z.com.

http://www.my350z.com/forum/showthread.php?t=125626

That thread shows that there are some motors with NA mods that are blown.
I thought that you can only blow the motor if you go FI.
can someone explain this?
Thanks.

 

simple....anything can blow at any time. Going FI just GREATLY increases your odds b/c of the extra strain on the engine.

 

so what causes NA motors to blow?

 

bad timing.. mis shift.. bad gas.. running lean.. too hot..

 

Same culprits in FI land. But I would have to assume much more rare in NA engines. The more stock...the safer it is....but nothing is perfect.

 

Among many things, inertial load - both compressive & tensile.

The largest compressive load usually occurs at bottom dead center (BDC) when the piston/rod assembly is forced downward during combustion and then stop sat BDC and changes direction.

The connecting rod's largest tensile load occurs at top dead center on the exhaust stroke. Since the exhaust valve is open the piston/rod assembly is accelerating freely without compression & BTDC combustion to oppose its movement. When the assembly reaches top dead center it wants to continue accelerating. The crankshaft stops the upward movement and basically yanks the piston/rod assembly back down the cylinder towards BDC. This produces a huge tensile load - the rods and rod bolts stretch.

Inertial loads go up with the square of the rpm increase. Therefore, high revs are not your engine's friend. Rev your engine 3000 rpm and the inertial load increases 9 times. At 7200 rpm the inertial loads are 144% greater than at 6000 rpm.

 

In lamers terms.... EXCESSIVE HEAT!

The NUMBER ONE reason NA engines fail, besides due to the obvious - improper or defective build / components is lack of lubrication (oil) which goes hand in hand with excessive heat...

It's all about thermal properties of certain metals and how / what we use to keep them cool and running smooth durring their everyday operation.

Loose, burn, or wear down your oil - and you're at risk of blowing your engine as well...

PS: By blowing up your engine, some people think your engine actually "blows up" but in reality, this usually means something internaly is leaking, slipping, loose, or has broken apart. Very rarely do NA engine's "blow up". I have seen rods break out from the side of blocks (personal experience on a supercharged big block I had in my truck) but that's usually due to the use of NOS or FI....

 

ducatiguy, so basically you're saying that to prevent from blowing up NA motors, we change the oil as scheduled right?