Old Chevy 350 truck w/ motorcycle oil

[kawie_guy]

Not sure if this is the best place to post this, but here it goes....

My dad has an old, restored Chevy 350, 3/4 ton, long bed pickup truck that he uses daily to take his dogs running. It's a 1976 but has parts from a 74,75, and 76. In 2001, he bought a new crate engine for it, but used the heads and some other things off the original engine. He thinks it's got flat tappets, but not 100% sure on that. It does not have a catalytic converter.
Anyhow, he's been using Valvoline 20w50 syn blend car oil in it, but he's found a good deal on some 15w50 high zinc motorcycle oil, and he'd like to buy a couple cases of it so he can use it in his powersport toys and that old truck if possible. Since there's no cat on it, I can't see where it would hurt, but I'm not very knowledgeable on those old Chevys.
If there are any Chevy guys here who would know for sure, I'd sure appreciate any thoughts you might have about this.
Thank you!

 

[SOHCman]

Use with confidence on an old flat tappet engine like that. ANy name brand diesel HDEO will work great as well.

 

[JeepWJ19]

Interesting. I've also been tempted to try it in the Jeep 4.0 but never did.

I'd be willing to try Valvoline MC conventional oil - it's what I use in my Honda CBR 600. It's pretty cheap and comes in 10w40 and 20w50 and can sometimes be found at walmart.

 

[Ducked]

You MIGHT lose out on friction modifier. Dunno how significant a loss that is likely to be.

I'd GUESS that any notional loss on friction modifier is more than counterbalanced by the (notional?) gain on Zn, but I dunno.

 

[BlueOvalFitter]

Originally Posted By: SOHCman
Use with confidence on an old flat tappet engine like that. ANy name brand diesel HDEO will work great as well.

^^^ This! ^^^
I have Chevy Orange running through my veins. Back when I raced/built engines/built hot & street rods, with my dad and others, I helped build/built well over 30 SBC engines. I/We would use QS, Pennzoil, Havoline, and Chevron oils. We used all weights, from SAE 30 to Kendall Nitro 70 wt. Most rebuilt engines were broke in on SAE 30 wt. and 10W30 was the go to oil.
Tell your dad to use that 15W50 with no worries.

 

[FCD]

50 grades are overkill.
The best oil for that would be Shell Rotella T4/75 15W-40, plenty of Zddp.

 

[Ducked]

Originally Posted By: FordCapriDriver
50 grades are overkill.
The best oil for that would be Shell Rotella T4/75 15W-40, plenty of Zddp.


You are answering a question that wasn't asked.

 

[Duffyjr]

Not sure how cold it gets in Utah but wouldn't 15/20w50 be a little thick for that engine in the colder months?

 

[BrocLuno]

Not really. The clearances are likely factory loose 0.0025+ and the same for the lifter bores. The 15W-50 is built around a 15W base oil and that is good down to 0*F any day of the week.

The issue with cold is battery and cabling to the starter, ground returns, etc. Make sure they are good and you'll be fine

 

[kawie_guy]

It gets cold here, but the 20w50 seems to be doing ok. We had a couple nights this winter where it got to 14 degrees Fahrenheit, and he reports that the old truck fired right up.
But I would bet the 15w50 synthetic motorcycle oil will do better on those cold mornings.