AMC V8 Oil?

[Brynjaminjones]

I have a Jeep Grand Wagoneer with an AMC 360 V8. This engine was rebuilt roughly 20k miles ago and runs/sounds great. It has an "RV-style" cam, but is otherwise stock.
These AMC V8s never have the best hot idle oil pressure, mostly due to oil pump design, and I generally see about 15-20psi at hot idle (600rpm in gear).

Because of this, I don't want to go below an xw40 oil.

The other issue I have is that these oil pumps can be a little slow to prime, meaning I can get a momentary dry startup/delayed pressure build if I use anything with too high an initial number.

Considering the fact that it's carbureted, which increases the chance of oil dilution from fuel, I'd like to stick to the thicker side, which means I'll likely choose something on the higher end of 10w40.

I know there's a lot of talk about ZDDP in flat-tappet engines. I've never worried about this too much in my Jeeps with the 4.0, but want to be a bit more cautious with this one.

I'm looking for some opinions on this - am I on the right lines, and how much should I really be worried about the ZDDP level?
Also, some oils that meet my criteria are 4T motorcycle oils - is there any harm in using these?

 

[burbguy82]

Motorcycle oil would be fine........ something in 10w40. I see you are in UK, what options are readily available to you.?

 

[Egg_Head]

I ran 5W-30 or 10W-30 in the 304 V8 in my old CJ-7 depending if summer or winter with no issues. Sounds like a nice rig you have. If your fuel lines are original or older, be sure to replace the fuel filter with every oil change.

 

[JavierH19]

What's the lowest temp it's starting at. At 0c a 10/15w oil will still pump quickly.

 

[GRUMPYDUDE2]

M1 0-40!!
Flows fast at start up. Nice oil film from start up to full temp.

 

[Brynjaminjones]

What's the lowest temp it's starting at. At 0c a 10/15w oil will still pump quickly.

It's rarely run at less than 5 degrees celsius. Even at higher temperatures though I get slightly delayed oil pressure on cold start, which is why I'm cautious.

 

[Brynjaminjones]

M1 0-40!!
Flows fast at start up. Nice oil film from start up to full temp.

The analysis I've seen seems to show that M1 0w40 is a little thinner at operating temperature than I would like, which is why I'm looking for something at the upper end of the 40 range.

Ideally I'd like an oil with a narrower viscosity range to avoid breakdown.

 

[K2K2]

Amsoil 10w-40 XL would be my choice.

5.2 NOACK, 4.6 HTHS.