I have a ‘68 L68 427 hydraulic flat tapped cam’ed engine so I’ve been running Valvoline’s high zinc formula 20-50 oil. It worked out very well thru the summer temps. It’d be at 70lb.s at start and drop back to around 35-40lbs running warm. Now that we’re in the colder temps I hear a lifter tap at startup for a few seconds which is seconds longer than I’d like. It’s not loud but its there. After a minute of running its gone completely. It’s a long minute though.
I know the importance of using high zinc oils with older flat tap pet engines and I’m of the mindset not to change brands at every oil change, mixing brands can create sludge. Pick something and stick with it. Valvoline makes 2 high zinc blends as I understand, 20-50 and 10-30. As I understand oil numbers the lower the first number the better it flows in cold temps and the higher the second the more it holds viscosity and higher temps. In these colder temps that tap I’m hearing seems to be asking for that “10” in the 10-30 but the running oil pressure at 35lbs seems to need that “50”.
So I find myself wishing Valvoline made the 10-40 other companies make but as the high zinc blend.
Here is what I’m wondering about is how crazy is it to consider using one or two qts of 10-30 mixed with the 20-50 staying within the Valvoline VR-1 oils blends.
In my head it would be based on the same blends so it shouldn’t sludge but may thin out that lower number to help flow at startup. I guess I’m mixing my own 10-40 blend (???)
How far am I off track here or does this seem feasible?

 

You make no mention of what engine speed you see the 70 psi or the lower number. I've used the 10W30 VR1 for many years on an LT1 based small block and have no oil pressure problems. See around 30 warmed up at idle and goes up to 60 warm at high engine speed.

 

Hey Lt.Mike, have you checked your rocker adjustments? I started having an issue on our '68 L71 because some two of the rocker arm nuts no longer held fast when I ran it through the gears fairly aggressively. They would back off just a bit, causing some noise. I thought about going to poly locks, but got some new Melling nuts and they appear to have solved the issue. I know the valve trains are different, but just a thought. Let us know what you find. Best, Paul

 

That would be at idle upon initial cold start and again at idle with the engine having been driven at operating temp.
The 20-50 is available in store but 10-30 has to be special ordered.
I’m considering ordering a case thru Amazon. Thanks.

 

Unless in warm climate and/or racing 20W50 is on the thick side. As mentioned above check for a loose rocker.

 

Your L71 is a solid lifter cammed engine which it’s recommended that you check/adjust the rockers every 2k.
Mine is the L68 400 hp version of the Tri-power having the hydraulic lifter cam. So what I’m pretty sure I’m hearing in the colder temps is the lifters being slower to pump up as oil isn’t flowing as well.
I’m leaning now towards changing the oil to the thinner 10-30 blend to see if is solves the startup tap and if it holds good running pressure.

 

would a loose rocker quiet down after a few seconds of operation ?

 

It's hydraulic, so if a valve is open at shutoff the oil will leak out of the lifter until pressure is restored at start up.

 

You don't need 20-50 unless you opened up your bearing clearances larger than stock. Your pressure seems too high. If you do not know your bearing clearances, I would run the 10-30 and see what the pressures are. You can mix in the 20-50 a quart at a time to get something in between but try using all 10-30 first is what I would do.

Rocker arm noise is another issue.

 

that’s what I figured plus with the heavier oil compounded by the lower temps it’s taking longer than I’d like

 

Agreed

 

Mike,
Lucas makes a Hotrod Hi-zinc oil in 10-30, 10-40, & 20-50, I think it compares favorably to the VR-1. 20-50 is pretty stiff unless you are running around the desert or your engine has wide tolerances. I run lucas 10w40 in the summer and VR-1 10W30 in the winter-(I use the Valvoline because I happen too have a number of cases). When I go to 10w30 my oil pressure drops 5 lbs at all temps and rpms. Oil changes are cheap and a lot easier than ripping into your valve covers. You won't hurt anything by running 10w30, give it a try and see if your valve quiets down... If you can still hear it then its time to get the stethoscope out....(Might be time anyway if this tap is something new)..

60

 

Mobil one 0W-40 is 1000 ppm zinc. Flows pretty good cold.

 

Driven Racing Oil (formerly Joe Gibbs Oil) has a few varieties that may work for you. They have a synthetic blend GP-1 15W-40 that has the zinc you need. They also have a "Hot Rod" series oil in 10w-40 that is a full synthetic called HR6. I use the GP-1 15w-40 and it works very well. Its pretty reasonably priced compared to some of the other boutique brands like Lucas or Amsoil too.

 

I have never heard that it would create sludge. At least not with modern synthetic oils. Where did you read that?
IMO, this is a good read: Motor Oil 101 - Chapter One - Operating Temperatures and Viscosity - Bob is the Oil Guy You may want to consider reading all the chapters.

I use 20W-50 for a number of reasons.

*I do not drive the car in the winter (except in extraordinary circumstances

*The engine builder recommended it

*I track the car in Time Trials and HPDE

I am considering an Accusump to pre-oil the engine.

 

mobile 1 synthetic 15-50 with 1100 zinc at walmart.. you pick up a little lower temp coverage.
i run in winter when i can and stable oil pressures summer cold or winter cold start up rpm / pressure.
maybe try it?

 

Valvoline claims there to 1,400 zinc in both 10-30 and 20-50. Don’t really see those numbers in other brands. Does it need to be that high ? Don’t know but don’t want to wipe a cam to find out.
I use Mobil-1 exclusively in my more modern roller cam’ed engines. Had the serpentine belt come off my 5.7 GMC once when my wife had it. She didn’t know what to do so she drove it home.
That was about 10 miles away. When she got home the radiator was near dry and it took more than a half hour for the temp needle to come down from being pegged. Later on I found out the filters rubber gasket had melted to the block. Once it did cool down I added water to the radiator and turned the key… it fired up and ran like nothing ever happened ! No apparent damage ! I was sold on Mobil-1 after that.
My main concern with my older engines is the zinc. I’ve built engines but I didn’t build this one. Really don’t know how tight it’s tolerances are so is 20-50 necessary ? When I switch to 10-30 I guess I’ll find out. If I ever do rebuild this engine it’ll get a roller cam but I’m a believer if it ain’t broke, don’t fix it. Gotten older and really don’t want to either these days.
Btw I'm in NJ so it does get cold and if there’s no salt on the road I will have the car out. Heck I have motorcycles and ride them year round too. Before retiring weather permitting I’d make those annual rides into work on Christmas and New Years could be 20 degrees but it gave my Officers a chuckle and a smile.
I’ve got the heavier oil in it now because for some reason 20-50 is available in store but 10-30 has to be ordered. When I brought the car home in February it desperately needed an oil change. I would’ve used Mobil-1 but there’s that flat tappet issue and the only available oil at hand that claimed “high zinc” at hand was the 20-50 Valvoline VR-1.