Rage

I have finally confirmed the reason for my engine oil temp problem during extended WOT running. Insufficient oil flow rate through the oil cooler for 625hp. An engine builder/mechanic built a pair of Whippled 496's for a 47 foot tub. So ~650hp though he claimed they dynoed 731hp. The engines are run at WOT for extended periods of time to push the heavy boat and oil temp was excessive. These have the same identical oil cooler as I do (Hardin 3x18 thermostatically controlled). Over a period of years of trial and error and insufficient success he finally increased the bearing clearances from 0.0025 to 0.0030 & 0.0035 rear main to increase the oil flow (through the oil cooler) and went from the 8-9 GPM Melling HV oil pump to an adjustable 15 GPM external oil pump to maintain the necessary oil pressure with the increased bearing clearances. That finally solved it.

I may eventually copy that but in the meantime I am looking for a work around that does not require pulling the engine and tear down. My first thought is to strap a radiator core style to the bottom of the crank case pan and run sea water through it to cool the bottom of the crank case and there fore the hot oil. Comment? Other ideas/products?

Baja226sport

iTrader: (28)

I might sound stupid, but have you tried bypassing the thermostat on the cooler? And have you checked to be sure there are no restrictions in the cooler?

Rage

No restrictions in the cooler since it will cool even the hottest oil down to the 190F thermostat setting and the oil pressure before and after the oil cooler is the same. The thermostat is the bypass that closes at 190F so all oil then has to go through the cooler @ 190F.

SDFever

IF you can somehow be certain that you don't have something wrong going on in the engine itself, why don't you start over with the oil plumbing and simply get it solved?

I guarantee you there is something wrong, crossed, or backwards somewhere in your system based on what you described a long time ago.

Send some detailed pics of your oiling system from block exit all the way to re-entry. Did you change any plugs on the block? Have you mapped out the oil flow to and from the oil filter adapter and the various options to use in terms of path?

Sumpim's not right sir -

Best of luck.

Philm

What are you calling excessive oil heat? is it hitting 300ºF?

Are you running the correct amount of oil? I ran to much oil at one point and the crank beat it up in the pan and made a bunch of heat. Dropped itdown to the correct level and the temps went back to normal.

GTOFFSHORE

What size lines are you running to the cooler? I would step up to a larger cooler. They do make bigger ones. And remember crank case temps are always high. What is it coming out of the cooler that is the question.

Raylar

I would have to agree with some others on this thread. If a 496 8.1L -suppossed 625HP engine is making the oil to hot for a thermostatically controlled 3"x18" full oil cooler, SOMETHING ELSE IS WRONG! I have built more of these engines in the world to +600HP and oil overtemp even after extended high rpm loads with that size cooler in a properly plumbed and set up oil system has never been a problem.
Please remember the good engineering mantra "NEVER MAKE ANYTHING MORE COMPLICATED THAN IT NEEDS TO BE TO WORK!"
Check and study your oil system and engine, something else is wrong and you can make exotic crazy systems to over engineer the problem fix or you can just go find a simple solution. Be smart, find a simple solution.

Best Regards,
Ray @ Raylar

Rage

270F and still climbing when I shut it down. I do not buy into the Merc Racing <or = to 300F oil temp is OK. Neither do any of the oil manufacturers

Yes, 10 qts per 496 spec. Tried one qt less like the HP3 race engines to reduce windage but still the same crank case oil temperatures.

Rage

190F (thermostate setting) out of the cooler regardless but 270F and climbing in the crank case at WOT.

Rage

AN10 lines and fittings. There are no detectable pressure losses do to the lines etc. since the oil pressure at the oil pump (before the lines fittings, oil filter, oil cooler etc.) is the same as at the cam bearings and mains.

Why? The current cooler,as I stated, is producing 190F oil temp out regardless what the crankcase oil temperature is.............because the oil flow into the cooler is not fast enough to keep up with the 625hp at WOT and therefore the oil cooler is loafing. Let us say that the oil flow rate is zero and at a perfect 190F oil out and because of insufficient oil flow (zero GPM) the engine oil temp reaches 1000F. That is not OK. Of course the lack of oil pressure would then become the issue but I made my point.