Quote:
Originally Posted by tnewland
I have an oil cooler with a 180 degree thermostat. The engine builder recommended 20/50 viscosity oil. The A/F ratio at 7300 RPM on one pull was 12.6 and on the second pull at 7500 RPM was 13.0, lean! The A/F at 6500 RPM was 13.2 and 13.2 during both pulls, so the engine was running lean during both full pulls with a max A/F of 13.9 at 5100 RPM during both pulls. |
Your engine had a relatively broad rpm range that it exhibited the mid to high 12.x to 13.x:1 AFR over. You have a legitimate complaint with your dyno operator. He shoud be monitoring the AFR during the pull and be prepared to abort the pull if the AFR numbers go the wrong way. To do a second pull without correcting the AFR problem is difficult to understand.
A 13.x:1 AFR is not good for your engine. I don't know how to reasonably set your expectations for potential damage. My expectations for damage at a 13.x:1 AFR would suggest the damage would be proportional to the duration of time under load at that AFR and how often you did it. Repeated abuse (detonation) could eventually get a rod bearing. Occasional occurrences would probably limit the damage to the rings and potentially the leanest pistons.
Your
oil system sounds like it should be adequate. Having said that, it is always worth the effort, after one of these failures, to take a careful second look to make sure all the "stuff" is assembled correctly and in working order. I know this next comment sounds dumb but don't forget to be sure the engine had/has enough oil in the pan for the modified, increased capacity oil system.
Ed
p.s. An afterthought: As some others have already observed, your oil pressure appears to have some fairly large swings from hot to cold. While cold engines normally have high oil pressure, engines at operating temperature do not typically loose as much pressure as yours does. Sometimes when you see these types of swings in oil pressure the engine is telling you it has a hurt rod bearing (or very large oil clearances). There is the possibility the insert was already toast when you got to the dyno. A potentially bad insert not withstanding the two pulls at better than 13:1 AFR did nothing to help.