just recently had bad valve guides replaced( a couple had droped 1/2 inch) so some oil was getting to the combustion chambers causing some detonation anyway , while heads were off I seen some strange wear patterns in a few cyl's , so I was going to re ring and put new bearings through out, well something went wrong ( think I mixed the rod caps up, or torque'ed two of them wrong) and chew'ed two of the rod bearings up.so I had to get the (stock) crank turned .010 mains .020 on the rod's , the machine shop said that the crank was bent,but that they was able to straighten it, was.025 bent , now every thing checks out ok but can detonation have bent the crank? was never droped or layed on it's side the mains did not look like they were scatched at all, does this sound possible?

 

Detonation can go as far as breaking a crank in half. However, usually a head gasket gets pushed out before the cranks goes.

 

never blew a head gasket , also found that the valves were not seating well so mabey they were letting some pressure bleed off when it detonated?

 

Sorry, oil does not cause detonation. Enough oil can increase cylinder pressure but usually by that point it begins to foul the spark. Certainly if you hydrolocked the cylinder, that could bend a crank. But to fully understand what happened, ask the shop where it was bent and even more critical, how they straightened it.

 

yes the plugs were wet with oil , but if oil get's mix ed with 93 octane won't it lower the octane rating of the fuel enough for it to detonate with 11.4 -1 cr?,at the end it was pretty bad smoking like the rings were gone , all the oil was draining down the guide like the drain in the sink!was using a lot of oil at the end.

 

NO!

Oil does not cause detonation. What makes you believe your problem was from detonation anyway? If the oil did anything regarding the firing of the cylinder, it delayed or stopped it from happening. Not as you suggested in causing it to preignite.

You have to understand that something that does not burn has no octane. Mixing something that doesn't burn with high octane does not produce a lower octane product. Low octane burns more rapidly and is quicker to burn, more uncontrolled if you will, not the opposite. That is:
High octane burns at a more controlled rate and does not have a tendency to preignite.
Low octane burns at a faster rate and has a tendency to preignite. So low octane is more "volatile".

Do you see now?

 

http://64.65.63.61/forums/showthread.php?t=420159

Somewhat similar thread with some different opinions.

 

Yeah.... oil has a octane rating of around 81 so you tell me if that's going to cause detonation or not?

Back in the good ole days of the Engine Masters when they didn't limit compression ratio AND the amount of rings you could run oil control was VERY important because of this.... especially with that junk 91 octane Shell gas.

Bret

 

Who told you that oil won't burn?!!

 

Ummmmmmmm

 

It's certainly true that oil in the combustion space is pro-detonation. As to the "why", I can't say. The compression argument seems a little sketchy to me, as the volume of oil is not large. So, I am more inclined to believe oil lowers the detonation resistance of the mixture. But there may be other explanations as well. No matter though, it does happen.

Rich

 

Oil will definately burn. Ever see an iraqi bbq? Usually in a car it isn't as bad. Mosquito killer anyone?

 

Someone please show me any document anywhere (or direct me to it) that says oil in anyway shape or form will cause the mixture to have a tendency to detonate. PLEASE.

And then maybe explain how that could account for the failure this guy had. But that is beside the point.

 

I don't have any independent verification. But if you ask 100 engine builders I bet you get the same answer from them all. Admittedly, "conventional wisdom" may be in error. But still..........

 

The gm service manual list excessive oil in the combustion chamber as one of the checks for detonation/spark knock.