Thread: Oil Temp To High 400 Small Block

Tweet

ANYBODY KNOW WHY MY OIL TEMP IS IN THE UPPER 300'S?

You're turning too many rpm, you don't have enough oil in the pan/sum is too small, your headers go by the oil filter, you have a lean condition in the engine, your bearing clearances are too tight, your compression is too high, you need an oil cooler, you have freshly honed cylinder walls causing excess friction, your ring gaps are too tight causing excess friction, etc...

How is your coolant temp?

that one goes under "etc..." I always have a backup.

Thanks for your response,


I built two 400 small blocks for a boat w/.20 over with JE pistons 9.0 comp,bore to piston .005 clearance ,standard rings .002 extra clearance on the ring gap, cranks cut to .10 under size, I checked every journal with plastic gauge and the clearance is on the loose side. I also installed a high volume pump w/ six quarts in the oil pan (mobil 1).

The engines rpm stays around 3000 with a max of 4200. I installed a set of world cyl heads and a oil cooler (water to oil). The fuel mixture is great I checked it with an oxygen sensor. The engine water temp is 160.
The idea of the exhaust near the oil filter was great but not for my application. The exhaust on the vessel is water cooled. I feel I covered all my bases but I still deep frying. I have the bypass valves blocked. The timing is perfect and some one else mentioned to me that blow bye could also do this but I don't have much at all. When building these engines I really took my time and double checked all clearances. Please help..............

The only difference between boat engine and car engines is that the runtime is measured in hours instead of miles. How long have these engines been running since you put the new pistons in? How big is the boat? What kind of prop are you running? You may be overloading the motors because you have too aggressive of a prop. Those motors should be safe to cruise at 3500 if you did a good balance job on them, so you could use a shallower pitch on your prop and still get the same speed. It just seems odd that both motors would be having the same problem.

OK, #1 with a boat your oil pan gets no air flow unlike a car. Get yourself a bigger oil\water cooler. #2 For a boat your RPM is on the low side. @3000 RPM your lugging the motors and that will bring the oil temp up big time. Your motor temp wont show this because its not a closed cooling system.
I do know alittle something about this. At this time I am a fulltime student in a mercury marine program 8 hours a day five days a week.

i also built 2 400sbc's for my boat and my oil temp seems real hot,although i have not put a gauge on it.and i have no idea of how hot they were before with the 350's. my best guess is that my hi volume oil pumps carry the oil too fast through the stock oil cooler."heat transfer"i have old cast iron chriscraft oil pans that hold 8 quarts .i'm think of a larger or secondary oilcooler .
i did get a kick out of the other replies
would like to share more info"props/cams/speed/boat/ (buzzardlu12@yahoo.com)

I stumbled on this site looking for the same answers, (oil temp)

I too have a SB in a boat (airboat) and I am concerned about the oil temp, only because this will be my 4th motor in it..however the last and final I asure you (according to my wife) which is a zz4 from Chevrolet with a hot cam set up.

This past weekend I read on my oil temp guage 210 to 215 F.
I am taking my reading right out of the oil cooler adapter (before the cooler) I wanted to read the hottest the oil will ever get, not after it was cooled. Maybe this is not a good Idea, but that is what I need to know.

Where are you taking your reading? My last 2 motors I took the oil temp from the pan.(thermal well with manual guage) What weight oil do you use? I use 10w40 Royal purple for now...that can change...

I also built my last 3 motors and 2 of them were sent to race shops in the Houston area for rotating assymblie balancing. But those motors didn't have the tolerance this new motor does from the factory, I just hope it will stay together because 2/3 of its life I will have my foot in its @$$ at 4500.

No, that is not the best place to take oil temp. Oil temperature guages take readings from the sump because that temperature best represents the temperature of the oil just before it enters the engine. You are interested in the temperature of the oil enterying the engine because you are concerned with viscosity. A low temperature means too high of viscosity and you will have trouble pumping the oil and could damage the oil pump if you rev the engine too high. High temp means low viscosity which means the oil might not be capable of lubricating important parts like bearings.

FYI, coolant temps are taken as coolant leaves the engine because it best represents the operating temperature of the engine. Viscosity is not of concern when dealing with coolant.

hi volume oil pump is the culprit here on a boat there is not a ideal way of cooling oil the extra oil volume doesnt give the oil any time to cool try running a oil cooler that uses a fresh water exchange that is seperate from the engine cooling sytem.

i agree with the boat mechanic , my little mercruise 151 4 cyl s oil is always really hot even thoght the motor hardly ever runs warm as it has all the cooling of whatever lake i am in. my boat does not have a oil cooler but the theory is correct the only way to cool the oil is through contact with the block or through the pan.
but the idea of a high flow oil pump may also cause cooling problems. i would still think a larger cooler wouldnt hurt the problem and probably solve it.