New owner to an old school. Picked up a 1969 cutlass with the 455 & Th350.
drove it for 2 weeks no issues. Thought I would change the oil to be safe. Put 10-30 in it and now oil pressure is good on initial start up & driving but once warm and comes to idle it drops to 1-2 psi.
Is this normal? Should I put thicker oil in?
not sure if it could be a clogged oil filter or not I cannot change it yet due to the header being in the way of removing it… fml

 

10W-30 should be fine. Using thicker oil isn't going to gain you 25 PSI. 1-2 PSI, if an accurate reading, is dangerously low. I'm thinking (hoping?), though, that your reading is inaccurate.

Two things: 1) How are you measuring the oil pressure? Mechanical gauge? 2) What was the pressure before you changed the oil?

I guess I don't have to point out that there's little percentage in changing the oil without changing the filter. You better gain access to that filter.

 

^^x2^^
Way too low @ idle if the reading is accurate. R&R the oil filter ASAP.

 

Did the oil pressure light come on ? Check to see if the oil pressure sending unit is connected to the wire harness.

 

If you still have the old oil filter, use some tin snips to cut it open. Look for metallic flakes or other debris in the filter media. If it’s full of crud, you found the problem. If it’s clean, try another oil pressure gauge. Hopythe gauge is inaccurate.

I would think oil pressure that low would result in some bad sound’s coming from the engine. You might try some 10w40, or 20w50 if it’s only driven in warm weather. That will give you a few more psi of oil pressure, but it’s like putting a band aid on a gunshot wound. Don’t expect miracles.

Good luck.

 

455 and th350 was not a factory lineup in 69, nor were headers, so this thing has been monkeyed with. Cut the filter, and put a good gauge temporarily on it.

 

What oil did you use? Certain brands hold pressure more steadily than others. Your gauge could be crap, too.
Run 15w-40 diesel oil. The header is not in the way. Change the filter immediately.

 

Hope it's just a case of a lousy gauge. My 71 98 just has an oil pressure dummy light. It illuminated once and thankfully it was just the sender.

 

The light does come on at idle. It is a mechanical gauge. Hopefully somethings wrong with the gauge.
the header is in the way of the filter absolutely no room to get out unless header comes off. Soon I will get the header off, change the filter & check the inside of the old one. Currently the vacuum modulator on the trans popped out as well since the ear that the bracket bolt goes into snapped off at some point. Surprised it stayed in this long. I live in Canada but during the summer here is usually 20-25 so I only drive it on warm days. What oil is best to try first the 15/40 or 10/40?

 

I said 15w-40 diesel because it is going to have the most additives of any off the shelf oil. Realistically, you should be running a good/better oil with additives for flat tappet camshafts: Lucas Hot Rod, Brad Penn, Valvoline VR1.
I run a Wix 51049 with Hooker Super Comps and a QuickTime bellhousing. It certainly looks unserviceable, but the oil filter, indeed, does come out.

 

^^^THIS^^^

I run Rotella T4 15W-40 in both of my Oldsmobiles. It's a high quality engine oil that's generally available in bulk since it's designed for diesel engines.

Do you know what brand of headers you have? You might be able to get the oil filter off if you remove housing from the block.

 

I’m not sure of the brand. It looks like the previous owner ghetto rigged a lot of this car. Now my turn to fix everything 😑 I can’t even fit the filter wrench onto the filter. Might make it worth it thought and heat wrap the header while it’s out. That or do a relocation kit

 

You aren't planning to save that oil filter for a museum piece are you? Place a drip pan or whatever under the oil filter. Take a screwdriver, chisel, whatever and bash a hole directly into the oil filter at the most convenient location - preferably an angle which affords the best opportunity to gain leverage to remove it. If the oil filter is incapable of being removed with installed headers, there's no telling the last time it's been changed. We could go on & on w/ speculation on its last removal and why the headers were installed, but the fact is that oil filter can be removed - beat the hell out of it and it will come off.
There are numerous oil filter removal tools - have you tried a canister tool?

 

What does the oil pressure do when you give it a little gas ?

 

Unfortunately it sounds like a rebuild is needed unfortunately. Chances of a light and gauge being wrong aren't good. What oil filter, short or long? Try a later small Olds 307 filter so you don't have to remove the header for an oil change, ridiculous. Get VR1 20W50 for a band aid until it can be rebuilt.

 

when I’m driving or rev it it goes to 25-45 psi

 

Unless you know for a fact the last time the oil filter was changed your very first order of business is to R&R the oil filter.

 

I'll say it again -- if the oil pressure is at idle is actually 1-2 PSI, it really doesn't matter what filter or brand and weight of oil you use. You're still screwed.

What did you say the oil pressure was before you did the oil change?

 

If that is the case it will probably run a good long time. Change the filter and put some 15w40 oil in it and keep driving until you have the funds to go through the engine. Just baby it a little if you can. If it has 45lbs driving down the road that is more than half of the new cars.

My S-10 has had basically the same oil pressure as you for the last 100k miles and it just turned over 300K

 

This is a very good idea. I quoted this so you didn't miss it.

 

What kind of headers are on this car? I have never seen headers that didn’t allow for oil filter removal. Either the headers aren’t fit that engine in that car, the headers have been bent, or it just LOOKS like the filter won’t come out. Post a picture of what you’re working with.

The oil filter on my car is a tight fit, but it comes out easily. In fact, it’s harder manipulate the oil filter wrench around the filter than it is yo get the filter out.

 

My gauge was not accurate. It would read 10 to 15 psi at hot idle and about 30 psi at speed depending on rpm. The plastic gauge line was leaking. I plugged the port on the block (need to repair line). But I bought a mechanical gauge to see what the correct reading is. The mechanical guage reads 30 psi at hot idle and between 45 and 60 at speed.

 

Well that's good news for sure.

 

Unfortunately, that wasn't the OP.

 

I was just pointing out that oil pressure gauges can often be wrong and not jump to the conclusion the motor is necessary bad. My advice would be to hook up a mechanical gauge.

 

Yes, I know. No worries, I was just pointing out to Kenneth that he may have responded to the wrong guy.

OP stated that he's already put a mechanical gauge on it.

 

I had the same problem, cold had 60 psi when it heated up i had 8psi pulled the engine pulled the oil pan and found my main Barings were down to the copper..

 

update; I got the filter off and new filter on. Seems to be running better but on warm idle now it’s around 6-7 psi