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Old 11-09-2017, 03:03 PM   #1
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What oil viscosity in fresh SBC in cold weather?

Hello all,
I'm curious what viscosity oil I should run in my freshly rebuilt gen 1 350 SBC? It's got just half an hour run time to break in the cam. All bearing clearances are roughly 0.002". I live in the mountains, where it gets fairly cold in the winter. Periodically down to 0f but I only drive this truck on nicer (relatively) days. I was planning on running 10w30 VR1 Valvoline racing oil. Has a Melling high volume pump. Stock bottom end w/ Summit 1103 cam and LT1 305 cylinder heads. Weiand Streel Warrior dual plane manifold with 1406 Edelbrock carb.

Thanks for any help!
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Last edited by nikwho; 11-09-2017 at 04:11 PM.
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Old 11-09-2017, 03:48 PM   #2
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Re: What oil viscosity in fresh SBC in cold weather?

You could run 20w50 with a zinc additive or can use Valvoline vr1 20w50 if you want the zinc already without adding the additive. I run either one with hot temps or cold temps.
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Old 11-09-2017, 04:09 PM   #3
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Re: What oil viscosity in fresh SBC in cold weather?

you're on the right track for break-in and weight.. heavier oil for heat, light oil for cold..

also mind the tight engine and high output pump.. heavy oil may build too much pressure..

try searching sbc break in oil and several engine builder threads on various forums will pop up..

if you had a local shop do the engine work, ask them what they recommend for your climate..

or consult manufacturer's recommendations of the components you used in your build..

good luck!
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Old 11-09-2017, 07:08 PM   #4
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Re: What oil viscosity in fresh SBC in cold weather?

Your oil pressure is going to be pretty high with a new tight engine. If you don't like seeing you roil pressure gauge pegged you should stay with 10w30 and see how you like it. I'm going to try 5w30 this year. My mains are at .003" and the oil pump is supposed to be a stock oil pump but I have my doubts. My pressure is always very high when cold and never gets below 30psi at idle when hot. If the pressure gets too high when cold it will bypass the filter which isn't good.
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Old 11-09-2017, 10:17 PM   #5
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Re: What oil viscosity in fresh SBC in cold weather?

Unless you're using it very hard for some duration anything thicker than 10w40 is unnecessary. If I was gonna put 5w30 in any small block it'd be something like your scenario - fresh engine, cool weather, gentle use. The high volume pump should make it even safer to use thinner oil as it'll further guarantee good supply.
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Old 11-10-2017, 12:13 AM   #6
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Re: What oil viscosity in fresh SBC in cold weather?

I would go with 10W30 as well and see how it does. If the pressure is too high when cold, consider going with 5W30.
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Old 11-10-2017, 11:12 AM   #7
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Re: What oil viscosity in fresh SBC in cold weather?

10w30 will work in dang near any conditions. Heck even newer rigs with tighter tolerances run 5w30.

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Old 11-11-2017, 10:23 AM   #8
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Re: What oil viscosity in fresh SBC in cold weather?

Id try 10w30 or 5w30 i use to run 20w50 and man my truck was hard to start when ti was 20 degrees outside and would peg the gauge out
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