Hi everyone. Looking for an opinion. Last summer my original stock 1969 455 was losing oil pressure at low rpm after the engine had been run for a while...maybe an hr or so. Could this be a sign of a bad oil pump or worse? If pump could be the problem, how big of a job is it? Can I do it from under the car?

Any advice is appreciated.

 

Please give more details on how you feel it's losing pressure. What are your cold and hot oil pressure at idle and at cruising?

 

Low oil pressure is far more likely due to excessive bearing clearances. Oil pressure naturally drops as the oil heats up and thins out.

 

So rebuild time?

 

Given how little information you've provided, it's hard to provide useful info. How many miles on the motor? What oil are you using? What are the cold and hot oil pressures at idle and at speed? How do you use the car?

 

The donor delta 88 had about 80k on it. I believe the engine to be original. I cannot recall the exact numbers on the gauge from last summer. I know at stop lights the needle seemed to almost hit the peg. I will get it fired up soon, and get it out and take some video or pictures of the gauge.

Thanks,
Bob

 

At 80K miles, you need to replace the timing chain and plastic cam sprocket at a minimum. I think a freshening of the engine would not be a bad idea.

 

Also, I run mobile 1. I put 10w30 in orginally, went to 10w40 to see if it helped...it didn't. On a side note, i have changed the oil 3 times in maybe a 1000 miles I have driven it. It gets coal black so fast, I figured it would not hurt to change it more often. I should be able to get it out tomorrow if the sun stays out like it is. They salt here, so I cannot take it out until it is dry.

 

Thanks Joe. I think you are probably right. Looks like its a no car summer.

 

How low is "low"? Eg, my current build has 60psi pressure at idle when cold, falls to about 15psi when hot.
As long as you have 10psi+ at hot idle, and pressure builds quickly when the engine revs, then it's fine. You can go thicker, too. All depends on what you want out of the engine. Just want it to live for another 30 years? Throw some 20w50 in it and cruise.
Want a ripin' snortin' monster? Yeah, needs a rebuild.

 

Have you put a mechanical gauge on it?

 

Rv,

Before you make any rash decisions I would put a good mechanical oil pressure gauge on it and see what it really reads. As long as the pressure comes up as soon as you hit the gas some I would not worry too much about it right away. It most certainly has some wear on it but as long as it has about 10 lbs of oil pressure for every 1000 rpm then it will be ok.

The 2.8 engine in my S-10 truck has just about 300K miles on it and when it is hot and idling it probably does not have 5 lbs of oil pressure. But as soon as I touch the gas it jumps up to 25-30. It has probably been that way for the last 100K miles.

 

As mentioned, before doing anything, install a different gauge just to verify what the oil pressure actually is.

Next, remove the oil filter and cut it open. Use tin snips or some other way of cutting open the filter that won’t cause metal shavings. Look inside the pleats of the filter, if you see metallic grit you know something is wearing inside the engine.

If you have a clean filter, the engine has no bottom end death rattles, and runs fine, but the pressure is lower than you like, you can band-aid the symptom with thicker oil. If you normally use 10W30, some 10W40 or 20W50 will definitely improve the pressure. Don’t try and start the engine in cold weather with the 20W50, the engine won’t like it. If you need to drive it in the cold, some Shell Rottela 15W40 might be a good compromise.

In my experience, as long as the low oil pressure is caused by slow gradual bearing wear, an engine will run forever with low oil pressure. It seems like once a engine suffers sudden damage/wear that things go downhill quickly