sbc oil viscosity

Joined
Apr 11, 2019
Messages
156
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
 

GA Architect

SILVER Star
Joined
Feb 14, 2014
Messages
3,662
Location
Woodstock, GA
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 ViscosityRod Bearing
Clearance
Main Bearing
Clearance
20w / 5w20< 0.0021<0.0020
30w / 5w300.0021 – 0.00260.0020 – 0.0025
40w / 10w400.0026 – 0.00310.0025 – 0.0030
50w / 20w500.0031 >0.0030 >


Driven Bearing Clearance vs Oil Viscosity

Main Bearing ClearanceOil Temp Less
than 160 F
Oil Temp
160-220F
Oil Temp
Over 220 F
Iron Block
0.0034-0.003910w40 or 15w4015w50-20w5020w60 – 60w
0.0028-0.0033 5w30 or 10w3010w40 or 15w4015w50-20w50
0.0022-0.0027 0w20 or 5w20 5w30 or 10w3010w40 or 15w40
0.0016-0.0021 0w10 0w20 or 5w20 5w30 or 10w30
0.0010-0.0015 0w5 0w10 0w20 or 5w20
 
Joined
Nov 11, 2019
Messages
116
Location
Texas, Is there anyplace else??
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.
 

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