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. M1 HM 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 RTS 5W-40, because I can rev better and freer with that than GTX 10W-30 or 10W-40.

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