Reed Jensen

Another thing to check is the fit of the distributer to the block..... if the distributer is too loose in the block it will allow the oil that is intended to go to the lifters on the right side of engine to just leak back into the sump. Hence low oil pressure..... again.... oil is like water.... it takes the path of least resistance. Anywhere oil is bled off it will decrease the pressure. The entire oiling system is like a controlled leak.... you just want it to leak in the right places! Good oil won't begin to coke up until over 400f. I had an air cooled motorcycle and the oil on that engine ran 350 f ! I could have deep fried chicken in it! The oil didn't discolor or burn... it just broke down quickly and would lose it's lubrication properties, so I had to change it often.

Mbam

Where are you measuring the pressure?

blue thunder

Here is a picture of a main bearing that was in an engine that the oil temp got to 280F. Unfortunately it was dino oil (straight 40) and couldn't take the heat. It broke down, lost it's cushioning ability and caused crank to bearing contact. This engine still ran strong and had 60psi warm at 3500rpm. Idling it was around 10psi. Before the hard run it stayed about 40psi warm idling. Cutting open the filter revealed the flakes of death but also saved me a lot of money because I didn't spin a bearing.

Reed Jensen

MMMMMMMMM....... Flakes of death! lol So many times people get "hung up" on oil pressure. I'm beginning to think some guys measure the length of their **** by how much oil pressure their engine makes! Boat guys talk about 60 psi and 80 psi... I work on old Aston Martin engines... AND THOSE GUYS DO MEASURE THE LENGTH OF THEIR ****'S BY THEIR OIL PRESSURE! A freshly rebuilt DB5 or DB6 engine will make 125 psi .... even when hot! These guys are crazy. All this extra pressure is an attempt to stave off bearing and cam failure because of poor design from the factory. I like to measure the oil pressure on a tall block at the hole at the very front of the block.... by the right head. It is the very furthest from the pump.... and thusly the weakest point... I know that if I have pressure there.... I have pressure everywhere. I ran 10-40 dino oil and after a high speed run,,,when the engines came down to idle.... the most oil pressure I would see was about 25 lbs. I didn't worry about it because I knew the main and rod bearings were getting oiled.

Reed Jensen

Here is something for you guys to ponder. If you are running a pump in the sump... ( melling, chev, merc, etc etc) . These pumps are designed with space limitations. The pump was originally designed to pick up warm oil,10-40 w, push it through a filter ( most of which goes through the bypass) and down the passage in the block to the main bearings, through the crank and to the rod bearings, along with oil being bled off to the cam bearings, lifters, rockers, etc. The total volumn of the oil being pushed by the pump is about 1 1/2 qts. Now that little pump is put in a boat.... and for the sake of tempurature control.... that oil is being pushed out the block,through a hose, up to a remote filter, down another hose, through a remote cooler, back through another hose, and then into the block. Total volumn of oil now having to be pushed..... about 3 qts, plus it has to be pushed through about 10 feet of hose. Right now that pump has to keep moving twice the volumn of oil flowing before it lubricates anything. Starting to see my point? A lot of the oil can't be pushed fast enough so it just flows out of the pump through the pressure relief valve. If you measure the oil where it first comes out of the block.... it will be high, because it is the static pressure within the pump. But by the time it gets out to the bearings,,,, it isn't much. Try this experiment. Try blowing the water through a 25 foot garden hose. I'm sure you will agree that no matter how hard you blow.... there isn't much water coming out the other end..... I prefer to run a thinner oil at a hotter temp so that it flows easier.... Look at the oils they run in new Chev car engines.... 5-30 oil... and those engines don't suffer bearing failures all the time like boat engines do.

blue thunder

I think people run higher viscosity oils in boats because the valve train creates so much more oil temp than does automotive. The trick is to not run hard until the oil is up to normal operating temp and therefore the viscosity is appropriate for the flow restriction of the marine system.

I guess we are talking to ourselves now because washed away seems to have disappeared.

Dave

Reed Jensen

I'd like to know your theory on why the valve train in a boat motor is hotter than in an automotive engine. Reed

blue thunder

Higher sustained rpm in a boat. What are you thinking?

blue thunder

That wasn't much theory I guess. Maybe this will be better: Higher rpm allow less seat time for the valves so they run hotter. Also the valve train itself spends more time (due to rpm) under the load of the valve spring. All in all, much more heat than typical auto.

Dave

Reed Jensen

MMM.... yeah,,,, the exhaust valves do run hotter. Especially if the motor is blown. Intakes don't run that much hotter.. a little due to the cycles and extra heat from supercharging and there is a little more heat from hysteresis from the springs. But the load on the cam bearings and rocker faces remains constant. Just more friction from movement. I would think that if you held an auto engine on a grade for a couple of hours you would see comparable heat.... ok... you win... boat valve train does run hotter. But you still have to have oil flow from the pushrods up to the top of the engine to dissapate the heat into the oil.... So I still think thinner oil is better! Just so that you know... the lifters in my motors were crane roller hydraulics, and the tech staff at Crane told me those lifters were designed for auto engines and will not pump any oil up to the rockers if it was thicker than 10-40 at 200 degrees f. So I was especially pissed off at the guy that put straight 50 w oil in the engines. I wondered at the time why the roller rockers were worn out after 5 hours too.After I spoke to the tech department at Crane I knew!