Synthetic oil and denial

[Perry]

Search engine here didn't yield tons of result for me. But Think I already know the answer to this.

I have a high mileage 440. Lots o miles but it is clean internally and serviced well. During the last tune up I put in Mobile 1 synth oil instead of the regular stuff. 10-30 like I always use. Warmed the engine and drained the old stuff out the best I could. Prefilled the new filter, etc.
About 15 minutes into the test drive and the motor started rapping pretty well. Not sure if it is a rod bearing or lifter or whatever. Still runs good and if I was deaf I would have thought wow, this is great. I searched around the internet and read various articles where people say this happened to them. Read a lot of articles where people have had no problems.

So the denial part. If anyone else told me this story I would say. Yeah, makes sense, your engine is ancient and the synth cleared away some sludge and exposed problems that were already there lurking. I did the knee jerk reaction and put regular oil back in and the noise was reduced quite a bit but the rap is still there. Muted but it stands out like a jack hammer on my brain.

So is there any thing to this? Read a lot about zinc content and impact on flat tappet cams but there is a lot of conflicting info.

Also, any suggestions on where I should investigate? The noise is only prominent when I am cruising and feathering the throttle between accel and decel. That soft spot. No noise during accel or decel.

Perry

[Chryco Psycho]

New oils are designed for new engines , the government wants old engines off the road .
start with valve train , you can pull the lifters with a small strong magnet through the head without removing the intake , just the valve covers , rockers & pushrods .  I assume the oil pressure is the same as before ?
The brgs should not care what oil is used as long as there is a supply of oil there . 

[Perry]

Thanks for the response. I didn't know that you could pull the rockers without taking off the manifold. I looked under the valve covers and found nothing interesting. So what would a guy be looking for when inspecting the lifters? Outside of the usual visual damage?

My oil pressure was a bit higher with the synth but now it is back where it started around 40-60 psi although it drops to 15-20 at idle.

Perry

[shadango]

" you can pull the lifters with a small strong magnet through the head without removing the intake , just the valve covers , rockers & pushrods . 

I didnt know this either.....    How is that possible?  The lifter wont fit up thru the pushrod seals....... Or is this just on this particular motor??

[Chryco Psycho]

the gaps between the ports on the heads easily allow a lifter through , small block is a bit tougher but you can feed the lifter through the adjacent gap & move the lifter over to the lifter bore . I have a small magnet that will lift a 1/2 drive rachet or more & a long thin screw driver , I slide the lifter into place with the magnet & hold it with the screwdriver while I remove the magnet when I re-install the lifters .

[dodge freak 2]

yep, I have swap cams before without removing the intake. Mopar rules in more ways then one

[1970 RT Challenger 1970]