Due to work and kids, it will likely be a few days before I can start the car again but I will double check my oil pressure. Even if the gauge is inaccurate, it's the same one that was hooked to the last motor and this one is reading consistently lower. Again, the tech I spoke with last summer said that it was within the safe range so it appears that it doesn't cross some level of concern for Blueprint.
It has Doug's headers and new gaskets. I retorqued all of the header bolts last summer when trying to track down the noise but it's worth checking them again. I don't believe it's an exhaust leak unfortunately.
As for the oil choice, I hope it's that simple and that no damage has been done.
Shell Rotella is rated for gasoline engines too. While it wouldn't be the oil I would ordinarily choose, using it in gasoline engines is certainly not unheard of. The extra zinc is something that is widely understood to be needed for flat tappet motors but (unless I TOTALLY missed it) there was nothing in the document stating that it would hurt roller motors. I specifically picked it to make sure I was obeying the recommendations.
The 4spd only has about 200 miles on it! The clutch is still being broken in. As for the miles with the old 904, I was have been weary of high RPM. Don't get me wrong, it has seen 5k but not often and not for long.
In any case, the motor seems to be running strong so I'm optimistic that it's not fatally wounded by whatever is going on.
I suggest you get on the phone and call a company like Torco, HPL or another small batch oil manufacturer and ask them about dual rated oils.
The additive package is different between the two and it’s so different they should not be used one way or the other. IOW’s, no one in the right mind would tell anyone to use a non diesel rated oil in a diesel.
I’ll say it again, 20 pounds of pressure at a hot idle is too damned low regardless of who says it’s good.
Let’s say your gauge reads 10 psi low (shows 20 when it has 30 actual) that is still at the gauge. There is many, many FEET of oil passages, sharp right angle bends and other obstacles to get around and over.
So what your gauge says is nowhere near what is happening at your bearings. It’s far less. Every time I pull an engine apart and see beat up cam bearings I know the oil pressure was low at idle. Every time.
So now that 30 pounds of pressure you have is maybe 10 pounds at the cam bearings. You have 16 valve springs pushing down on those bearings (obviously not all at once but there is a pretty good load pushing down on the bearings) and the cam eats the bearings.
Now follow the oil up the rest of the way to the rockers. You’ll be lucky to have 5 pounds there. And it could be zero. Same thing. Blued or scuffed shafts is a sure sign there wasn‘t enough oil there.
Pressure is resistance to flow. When you have little to no pressure you have NO FLOW. Pressure and flow go together. You can’t have one without the other.
This is one reason why I use high volume pumps on all my Chrysler builds. The HV pump gets more oil everywhere sooner so consequently the pressure goes up. Without that extra flow, the pressure goes down.
You need to figure out exactly what your oil pressure is and then make some decisions. It would be nice to know what your bearing clearances are and if you have half or full groove main bearings.
All of those things dictate oil pressure, as does the grade of oil. Sometimes you have to overcome builder mistakes in clearance with a higher grade oil, because it’s cheaper and easier to change oil than to unscrew bearing clearances that are too wide.
