MMO Clean = New Lifter Tick

[Astro14]

It is probably worth dropping the oil pan on this engine and checking your pick-up/screen...with all the chemicals breaking loose crud in the engine, and all the crud that you've said is present, you might have a partially blocked pick-up...

What's your pressure at idle when you have the ticking?

 

[Phishin]

The dash gauge says 35 psi at start up. Drops to 28 when warned up.

Today was a cool day. Truck never ticks in the morning at start up.

Today when I started it at noon for lunch, no tick. First time all summer that happened. Had to be temperature related.

I think my oil is too thin. Warn engine, plus heavy MMO, plus hot ambient temps = tick

 

[Brons2]

I've screwed together quite a few 350s in my time, along with some other small block Chevrolet engines (400/383/327). I agree with Trav to try adjusting the preload but I only used half a turn, not a full turn. However, he could be right here as yours one is a '90 and most of my experience is with older flat tappet SBCs using CompCams camshaft/lifter combos.

Otherwise...my advice is to back off with the cleaning for now and run straight oil on 3000oci until you have the tick solved. You don't need 15w50 + a homebrew. Delo, Delvac or Rotella 15w40 would work great in this old flat tappet 350. Mobil 1 High Mileage 10w40 is another good choice. If it doesn't tick then just use the engine normally without adds. Don't know how cold it gets there in the wintertime but a 5w or 0w40 may be necessary for winter so you're not trying to crank over molasses in the morning.

I would also take off the pan and check the oil pickup, just as a safety precaution after all the aggressive treatments that you have done. 35psi at cold start is not that high, my old 350s ran 50psi (at least) on a cold start. Of course, we ran 20w50 year round in Oregon in those days, we didn't really know any better back in the 80s

. Man, I miss those old days working in the shop.

 

[Jaymus]

I've been running Rotella 5W-40 for over 4 years in my 86 F150 5.0 EFI flat tapper cam. Different engines, I know, but anything thicker than that is just too thick. Even Castrol GTX 10W-40 really hurt my rev ability in the 4500RPM - 5000RPM range, guess it takes a lot longer to get to operating viscosity than Rotella T Synthetic 5w40, because I can rev better and freer with that than GTX 10w30 or 10W-40.

Great oil, great cleaning ability, and plenty of zinc and phosphorous for our flat tappet cams to work and play with.