sbc oil viscosity (1 Viewer)

[74bigred]

Hi Guys,
I have a small block 350 crate in one of my 40s. For anyone with the same motor as me- Curious what viscosity & brand engine oil you’re running.
I use 20w-50 in my other 2 stock Cruiser engines.
Thanks in advance for your input.
-D

 

[B y r o n]

Maybe this will help you understand oil viscosity.

 

[peesalot]

I have a 2001 6.0 liter and I run Mobil 1 synthetic 10-30, the 5-30 caused alot of lifter noise.

 

[GA Architect]

Hi Guys,
I have a small block 350 crate in one of my 40s. For anyone with the same motor as me- Curious what viscosity & brand engine oil you’re running.
I use 20w-50 in my other 2 stock Cruiser engines.
Thanks in advance for your input.
-D

I never knew, but ran across this the other day about, "Oil Viscosity & Bearing Clearance" -> click here <-

Bearing Oil Clearance Chart

Oil Viscosity	Rod Bearing Clearance	Main Bearing Clearance
20w / 5w20	< 0.0021	<0.0020
30w / 5w30	0.0021 – 0.0026	0.0020 – 0.0025
40w / 10w40	0.0026 – 0.0031	0.0025 – 0.0030
50w / 20w50	0.0031 >	0.0030 >

Driven Bearing Clearance vs Oil Viscosity

Main Bearing Clearance	Oil Temp Less than 160 F	Oil Temp 160-220F	Oil Temp Over 220 F
Iron Block
0.0034-0.0039	10w40 or 15w40	15w50-20w50	20w60 – 60w
0.0028-0.0033	5w30 or 10w30	10w40 or 15w40	15w50-20w50
0.0022-0.0027	0w20 or 5w20	5w30 or 10w30	10w40 or 15w40
0.0016-0.0021	0w10	0w20 or 5w20	5w30 or 10w30
0.0010-0.0015	0w5	0w10	0w20 or 5w20

 

[JAG666]

Hi Guys,
I have a small block 350 crate in one of my 40s. For anyone with the same motor as me- Curious what viscosity & brand engine oil you’re running.
I use 20w-50 in my other 2 stock Cruiser engines.
Thanks in advance for your input.
-D

-D;
I'm running a '67 Cadillac 429cid V-8 in my '74 FJ40. Not "exactly" like your SBC 350, but same "Parent Company".. The point I'm making is, your GM Engine and my GM Engine both came off the assembly line with the recommendation of 30wt for warm areas....
That said, in the late '60's, I switched to Castrol 20w50 in all my cars and use it year-round (I live in the DFW Area of Texas.. more hot than cold!)
I believe you can do No Wrong using 20w50. I also add a 4oz bottle of ZDDP (per 4/5 qts) at each 3000 mile oil change (ZDDP is Zinc & Phosphorus.. an anti-wear product) Around the late '80's, engine oil companies began reducing then eliminated ALL ZDDP from their products.. All "Flat Tappet" engines NEED ZDDP to keep the cam lobes from going flat!! (basically ALL "Pre-Emission" [non-roller cam] Engines require ZDDP-- but not to be used with Catalytic Converters!!).
If you are running a Roller Cam in your SBC, you need not worry about a flat-cam.
I just read that Castrol now offers a "High Zinc" 20w50 Oil.. I'm sure there are other brands that do, as well.
Charles 1974 FJ40.

 

[rstoddard]

Maybe this will help you understand oil viscosity.

Maybe this will help you understand oil viscosity.

So, is 20w-50 a good viscosity for the desert (Arizona) where it gets hot, but not too cold. So most of the driving is done in temperatures between 40*- 90*/100*

 

[B y r o n]

I'm no oil expert so here is some additional reading that may help.

As noted above, bearing clearance can affect oil weight choice. Factory street engines have tighter bearing clearances than race engines. Also, older/worn engines begin to make noise and the use of heavier weight oils will quiet them down. It will also sometimes decrease oil usage as it is harder to get past the rings and valve seals so less smoke and/or usage.