496ci professionally built motor with less than 800 miles on it. This just started today, where when I'm driving on the highway (flat road, not hilly) my oil pressure gauge will drop from 70psi to ~50psi for about a second then come back up. It does this intermittantly. Also, when I stop at a light the gauge will intermittantly drop to between 10-20psi. As soon as I accelerate it instantly goes up to between 50-70psi ,depending on how hard I get on it :). Car has never done either of these before. I am running a hi-perf hi-volume Melling oil pump and Mobil-1 oil. Should I be concerned yet?

Any ideas or suggestions are greatly appreciated.


1969 Chevelle SS "496"
http://www.mikesautoclinic.net/69chevelle/

496ci professionally built motor with less than 800 miles on it. This just started today, where when I'm driving on the highway (flat road, not hilly) my oil pressure gauge will drop from 70psi to ~50psi for about a second then come back up. It does this intermittantly. Also, when I stop at a light the gauge will intermittantly drop to between 10-20psi. As soon as I accelerate it instantly goes up to between 50-70psi ,depending on how hard I get on it :). Car has never done either of these before. I am running a hi-perf hi-volume Melling oil pump and Mobil-1 oil. Should I be concerned yet?

Any ideas or suggestions are greatly appreciated.


1969 Chevelle SS "496"
http://www.mikesautoclinic.net/69chevelle/
Mechanical or electric oil guage? Does it do it only when warm or when cold as well?

Mechanical gauge. Only seems to do it when warmed up. Will double check to see if it does it when cold.

Doesn't seem to do it when cold, only at operating temp.

I had the same exact issue on my 454 had less than 1,000 miles on it, pressure was great at hwy speeds, at idle would flucutate between 10psi and 20psi only when hot. Tried heavier oil no change within a week I ended up spinning the #1 rod bearing and trashing the crank and rod.

MERrY CHRISTMAS...lol..I am not sure what it is, but from his experience it doesn't look good. I hope otherwise.

I would contact the builder

What brand of oil filter????

Is the by-pass blocked off in the filter adapter??

Keith

Finally figured out the problem and figured I'd post the results in case anybody else runs into a similar problem.

Engine was running much too rich and over time the gas was "washing down" the cylinders and ending up in the oil. Definitely not good either way. Changed oil & filter and leaned her out a little bit. Running like a champ with no fluctuation in the gauge. Thank God!!!


496ci BBC 585hp @ 5300 / 599ft. lbs. @ 3500
www.mikesautoclinic.net/69chevelle