Jeff Lange wrote: > What is the max acceptable oil pressure for a Corvair engine? > What is considered the max continuous oil temp (we are using the > recommend Rotella oil)?
As you already know, adjusting that oil pressure relief spring only changes the upper limit of where the oil system dumps excess oil pressure back to the sump, so max pressure is raised, but the lower pressures reached once the oil is warmed up are still low. The usual answer of course is loose bearing clearances and that kind of thing. As you also know, the general rule is 10 psi per thousand RPM, so you are right at that limit. Having said that, I've flown with less, but only long enough to put a higher volume oil pump in it. Clark's makes at least two different versions in them and I've flown both with good results. They'll bring up pressures throughout the range, although more pressure will be dumped during cold operation. The "power robbing" point is the main downside of a high volume pump, but another downside with the Corvair is that the oil pump is run by the distributor drive gear on the bottom of the distributor. That gear has a slot in the bottom that turns the pump, and the gear is pinned onto the distributor drive shaft by a pin. That pin, subjected to enough shear, can shear in two, leaving neither pump nor distributor turning. I've heard of this happening, but don't know anybody personally that it's happened to. It's relatively rare, and may involve extenuating circumstances. If I'm not mistaken, William Wynne replaces this pin with something stouter, so this is an option, and maybe has already been done to yours. It's insurance against a problem that is made more likely by use of a high volume pump. Having said that, all of my engines have used a high volume pump except for a 2700cc experiment that I ran for a short while. Since I have a remote cooler and filter, I feel the need for a high volume pump, and will never go back. It does make a difference. To answer your question, most folks I know consider 55 psi to be just about perfect, and certainly not too high. On a super cold day with no preheat, it'll climb above that as the bypass valve is overpowered. If it gets over about 85 psi, I'll make sure my oil filter isn't puking oil before I take off, by doing a few donuts before takeoff. It happens! 220F wouldn't bother me, but the 29 psi at 2950 RPM is getting there. A high volume pump will certainly improve that. By the way, I never saw your CorvAircraft post either, so you may want to repost it there. You may have the old address. The new one is given at the top of http://www.corvaircraft.org/ . Mark Langford ML at N56ML.com website at http://www.N56ML.com --------------------------------------------------------
