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SBC Which Oil viscosity

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Zman57

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Discussion starter · #1 ·
What is the recommended engine oil to be used in a mildly modified 327. I live in NE Pennsylvania and the engine was rebuilt last year. Last summer I ran Penzoil 20-50wt GT performance and BG Zinc RF-7 that was recommended by the engine builder. I ran the car at the end of the summer when temps were in the 70-s to mid 80s. I probably put about 500 plus miles on the engine.
My concern is with spring coming I would like to run the car when the temperature's will be at 40 degrees plus, and obviously I don't want take any chances with the colder temperature's and possible engine damage.
Which engine oil viscosity should I be running when spring hits here??
 
#8 ·
Another option is Rotella 15w-40. I love the stuff. T4 for most stuff & T5(Syn Blend) for my bike. In the hotrods I do add a bottle of zinc with every change just to be safe.
 
#9 ·
As long as the car is in a heated or warm garage and you warm car before stomping on the pedal then the heavier weight is fine. So if you’re careful you can run the thicket oil just fine.

The thinner weight when cold helps with cold engine starts so if car is outside and you go some were and it cools down completely and its pretty cold out then you want a thinner winter weight to keep it from making high oil pressure.
 
#10 ·
Zman57 said:
What is the recommended engine oil to be used in a mildly modified 327. I live in NE Pennsylvania and the engine was rebuilt last year. Last summer I ran Penzoil 20-50wt GT performance and BG Zinc RF-7 that was recommended by the engine builder. I ran the car at the end of the summer when temps were in the 70-s to mid 80s. I probably put about 500 plus miles on the engine.
My concern is with spring coming I would like to run the car when the temperature's will be at 40 degrees plus, and obviously I don't want take any chances with the colder temperature's and possible engine damage.
Which engine oil viscosity should I be running when spring hits here??
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With a newly rebuilt engine 10-30 should be fine with zinc added or VR1 Valvoline. 5-30 is for newer closer tolerance engines and might be too thin for the old SBC. JMHO.:):bowtier:
 
#11 ·
5-30 is for newer closer tolerance engines and might be too thin for the old SBC.
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I disagree here. This comment might apply to an oil choice for an engine needing a rebuild or that will need one in the near future. It doesn't apply to a fresh rebuild using today's parts and machining methods. Even if it is a 327 rather than an LS.
 
#14 ·
Rick_L said:
I disagree here. This comment might apply to an oil choice for an engine needing a rebuild or that will need one in the near future. It doesn't apply to a fresh rebuild using today's parts and machining methods. Even if it is a 327 rather than an LS.
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Agreed. On my 421 SBC (full roller valvetrain) I used straight 30W for the break-in (builder's recommendation), moved to 10W30 for 500 miles, and after that oil change it's now on full synthetic (which is essentially 0 weight).

Also, on my 1991 Syclone (which is essentially an SBC, but is a V6) it's recommended to use full synthetic from the factory (also, full roller valvetrain).

Now...your mileage on seals may vary with full synthetic in an old SBC ;) I have a small rear main leak on my new SBC 421. Meh. Whatever.
 
#15 ·
If the car is never driven in the cold then straight weight oil is fine. Roller cams won't need the zinc or zinc additive. Also some racing oils lack detergents as well which isn't good if you put alot of miles on a motor.

The W is NOT for the weight of the oil. The W stands for "winter" not weight, this is the biggest misconception people have about oil. So 10W is the viscosity when cold and 30 is what it is under normal conditions. Straight 30 weight for example is typically labled SAE 30. If it was labeled 30W and no other number then its 30 weight when cold and hot for example. OW oil is zero weight when cold and usually 20-30-40 when normal temp. Not sure why you would want a straight 0 weight oil? As that is pretty thin under normal conditions for a street car.

The synthetic causing oil leaks is yet another myth. There is noting in that oil that damages seals. So usually the leaks from older motors with already worn seals, which back in olden days people swapped in the fancy oil with detergents which remove sludge and stuff which then causes leaks. Some car manufactures even recommend synthetics new, with NO break-in oil needed.
 
#16 ·
Zman57 said:
What is the recommended engine oil to be used in a mildly modified 327. I live in NE Pennsylvania and the engine was rebuilt last year. Last summer I ran Penzoil 20-50wt GT performance and BG Zinc RF-7 that was recommended by the engine builder. I ran the car at the end of the summer when temps were in the 70-s to mid 80s. I probably put about 500 plus miles on the engine.
My concern is with spring coming I would like to run the car when the temperature's will be at 40 degrees plus, and obviously I don't want take any chances with the colder temperature's and possible engine damage.
Which engine oil viscosity should I be running when spring hits here??
Click to expand...
The oil pressure relief valve will bypass excessively viscous oil back to the sump and starve the bearings of oil flow. Oil pressure is a characteristic of viscosity and flow and bearings need enough flow for hydrodynamic lubrication. See Engine Wear.

I would run any 30-grade multi-weight oil (ie, 0W-30, 5W-30, 10W-30, 15W-30) you're comfortable with. If your oil runs really hot and your oil pressure drops as a result, I would try a 40-grade (like 15W-40) before running a 50-grade oil (like 20W-50). See Corvair Oil Guide.

I would also go with a heavy duty engine oil (like Shell Rotella) rather than a racing oil because HDEOs have better detergents and will keep your engine cleaner longer. I like Petro-Canada Duron SHP 10W-30 in my flat tappet-cam engines because it is dual rated (API CK-4/SN) and also is approved for Ford WSS-M2C171-F1 (1000-1200 ppm of phosphorus). Excess ZDDP is not beneficial. See Engine Oil Myths - GM TechLink.
 
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