Valve rattling started today....

[shadowfax101]

It has been driving fine until my fience and I were driveing around this afternoon and we went up this hill on out way back home and the vavles just went to rattling. We can home and I had to go back and do the hill again to make sure that what I heard is what I heard. Sure enough they were rattling. Only notice it on this modest hill.

Could it be a case of bad gas. I did add a bottle of Marvel Mystery Oil to the tank on this last fill up. Could that have anything to do with it.

If it is not bad gas what is the next step to take.

[Bob Barry]

Is it the lifters rattling from low oil-pressure, or the engine pinging due to preignition?

[Gwamp]

Do the dollar bill test. Could be rocker arms also. Listen to all your cylinders with a hose or stethoscope. Exhaust leak maybe? Mine used to make a wierd rattling noise under load and it was the spacer between the carb and air cleaner. It was broken.

[shadowfax101]

Oil pressure is the same as always. Around 40 lbs at the time of the rattle. It was not pinging it was a weird sound of rattling of some kind. Did the dollar test and it did not suck it back in...

[shadowfax101]

Could this be the reason????

Like I said I added a bottle of Marvel Mystery Oil to this tank of gas. I have always heard the old saying if you put real good gas(high Octane) in an older engine and then go back to cheap gas you will get some valve rattling. Could this have been what happened. After adding the MMO it cleaned out years of crud on the engine, and after it was all used up(have about a quarter of a tank left) the lower octane gas stating running through and under a heavy load it started rattlng.

I hauled a decent side tralier over some large hills about a month ago and it was perfect, but now I have this rattle. I am hoping if I run some high octane gas it will be fine.

Could I be right?