5w50 in Pontiac V8?

Messages
273
Location
eastern WA
Hi all,

Looking for an oil recommendation for a Pontiac V8. 4.35 bore, 4.25 stroke, 2618 pistons, 505 CID, 10:1 compression, aluminum heads, forged crank & rods, Holley 850 double pumper. Cam is a retrofit hydraulic roller with just under .600 lift, 236 @ .050 intake duration and around 130 lbs of spring pressure on the seat. Real basic hydraulic roller hot rod engine. 65 GTO with a muncie four speed.

I’ve run the Valvoline VR-1 10w30 and Supertech 15w40. Both seem fine, the 15w40 has more pressure when really hot and the 10w30 comes up quicker in the cold.

I live in Spokane and we get some really cold days and some really hot days. Pontiacs tend to run hot and I sometimes let ‘er eat a little bit, so on one hand I’d like a heavier weight oil. At the same time, I find it really limiting to only drive on warm days and there are a lot of very cold but clear days where I’d be perfectly happy to drive my car. But the 15w40 seems a little thick for really cold days.

Is there any reason not to run something like a 5w50 Mobil 1 or Castrol Edge in this engine? Both of those seem to be widely available and reasonably priced. Seems like most of the old hot rod guys tend to run oils marketed more for that segment, but other than the flat tappet ZDDP issue I’m not really sure why. Seems like I could run a 5w50 and have my cake and eat it too, so to speak - drive the car any day of the year without thinking twice, no?

Thanks!
 

CheezWhiz

Thread starter
Messages
273
Location
eastern WA
I think the 5w40 and 0w40 suggestions are perfectly reasonable. I do sometimes get a lifter tick when fully heat soaked and have never run a 50 weight, so I guess that was part of the motivation behind the 5w50 that I did not put in the initial post- thinking it was worth a shot to see if a heavier oil would quiet the valvetrain somewhat.

Let me ask the question a different way - let’s say for this year I decided to try a 5w50 just to see how it goes. I mean I can always try something else, and it can’t possibly hurt, right? I mean - other than the zddp deal, which is a non-issue for my engine - there’s nothing about a modern 5w50 that is problematic to run in an old-style V8 for a year and maybe 2500 miles?
 

CheezWhiz

Thread starter
Messages
273
Location
eastern WA
I guess the other thing I would mention about the 50 vs. 40 weight issue is the carburetor. An old Holley tends to dump a fair amount of fuel into the engine. My engine is fairly fresh and well-tuned, and the 505 can eat up most of what an 850 Holley can throw at it. But still, fuel dilution is a potential issue and I guess it seems safer to err on the side of a heavier oil.
 
Messages
5,676
Location
Fort Worth, Texas
I think the 5w40 and 0w40 suggestions are perfectly reasonable. I do sometimes get a lifter tick when fully heat soaked and have never run a 50 weight, so I guess that was part of the motivation behind the 5w50 that I did not put in the initial post- thinking it was worth a shot to see if a heavier oil would quiet the valvetrain somewhat.

Let me ask the question a different way - let’s say for this year I decided to try a 5w50 just to see how it goes. I mean I can always try something else, and it can’t possibly hurt, right? I mean - other than the zddp deal, which is a non-issue for my engine - there’s nothing about a modern 5w50 that is problematic to run in an old-style V8 for a year and maybe 2500 miles?
I wouldn't say low zddp is a non-issue just because you have roller lifters......I've seen a noticeable uptick in Rocker Arm & Pushrod wear (Where the Pushrod & Rocker Arms meet), The fact that the Pushrod no longer spins/rotates with the flat tappet lifter only exacerbates the issue.
Just about every OHV roller cam engine can have wear in that area......I mostly work on LSx engines so naturally I see it more on those. Had a Ram SRT-10 with all 20 pushrods & rockers wiped out.
 

CheezWhiz

Thread starter
Messages
273
Location
eastern WA
i see, thank you. perhaps this is why you were steering me to the diesel oils in the first place?

i have some 20w50 vr1 i bought on sale. might just run the 15w40 in the pan until summer and then switch to the 20w50 just to see if it affects the lifter tick, then adjust fire from there.
 

SR5

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5,941
Location
Down Under
Here is a link to a PDF that has the zinc levels for all the M1 oils


Most M1 oil run between 750 to 900 ppm zinc.

M1 0W40 and M1 5W50 are both higher at 1100 ppm zinc, and both are also Porsche A40 rated. Both would be a good choice.

If you wanted an even tougher oil, I would go M1 15W50 with 1300ppm zinc. A very shear stable racing oil, that is also SN rated so good for road applications too.
 
Messages
266
Location
South
Stick with the Valvoline VR1 oil. Proper zinc for high valve spring pressures. As mentioned before there is still a need to address rocker arm/valvetrain wear regardless of this being a roller cam engine.
 
Messages
2,393
Location
Paradise of Florida
Roller lifters on cam lobe...no roller rockers on pushrods?

I was under the impression most issues were caused by bad manufacturing and not the low zinc. Probably still want to skip the API passenger oils.

I'd stick with HDEO and motorcycle oils.

Let oil temps and oil pressure help with chosing oil grade.

If it were mine:







 

Zee09

Site Donor 2021
Messages
5,190
Location
Fairhill Maryland
I think I will try the M1 15w50 and just take it easy on cold startup. Seems to cover all my bases that way.
I had a 67 Convertible full power with air in the day...
Mine was the big boat style. Then before anyone cared it ran 20w50 all year.
I traded it in on a 78 Cordova with a 360 LB engine and I ran the 20w50 in it too...
 
Messages
2,393
Location
Paradise of Florida
5w50 seems a bit of a spread for an engine. I wouldnt bother.
M1 15w50 easy to source ...

I remember thr Red/Gold/Silver cap changes and how the 15w50 temporarily turned into a pariah with a formula change. Hope M1 learned.
 

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CheezWhiz

Thread starter
Messages
273
Location
eastern WA
Here's a pic of the old girl. My first car, been in the family since the early 80's and I got her in high school, 1991.

353EA2C4-57A8-4855-AFD0-2B7475E4409E.jpeg
 

CheezWhiz

Thread starter
Messages
273
Location
eastern WA
Wow......nice car !
You drove that to high school, you would have been a king around here, most of us just rode bicycles to school.

I think it was green primer in high school, yellow primer my first year of undergrad, and then a paint job for the rest of “college” before I flunked out and joined the Army, lol. Got myself in gear and had it restored about 15 years ago, still fixing little things but it runs good, looks good, it’s a lot of fun.
 
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