Just for information/Comparison

I have a 1984 Trans Am 305 L69 (Carburetor) 5 spd.

The stock oil pressure gauge is not working, so I installed an aftermarket mechanical gauge I bought from Shucks.

When I first start the engine from a cold start it is at 40 psi for around 20 minutes. Once the car is warmed up the oil pressure fluctuates under driving conditions.

At idle or driving around town the psi will match the rpms. For example if the engine is idling at 900 rpms the oil gauge shows 9 psi. If the engine is at 2000 rpms the oil gauge is at 20 psi.

When driving down the highway at 65 mph in 5th gear the rpms are at 2000 rpms and the oil pressure is at 25 psi.

The engine is the original and has never been rebuilt other than the heads.

 

How many miles are on the engine? Does it run strong?

 

I've been trying to figure that out. The odometer says 20,225 miles. So it is either 120,225 or 220,225. I believe it is 120,255 with the original engine. When I redid the timing it still had what appeared to be the original nylon gears from the factory. They were cracked all over. I did replace the factory heads with another pair of rebuilt heads that I already had. The cylinders walls and pistons all looked really good after 26 years. Lastly, it still runs very strong and I have not seen any large oil consumption.

What are your oil pressure readings?

 

At idle, I get about mmmmmm I think about 30.

 

Kinda apples to oranges maybe, but my TBI 305 sat at 30psi at idle, and up to 70 psi when my foot was in it. Now I have an old carbed 350, and it's about the same. I can tell when it's oil change time, as my idle psi will fall to under 30 - happens almost every 3000 miles just like clockwork! Baby knows when it's time, and she never fails to tell Daddy!

 

Just an update.

In the past, I've been running Lucas oil quart with walmart 10w40 oil. I have never really seen a difference in oil, so I have just been going for price.

This time I ran Lucas oil quart with the Castrol GTX high mileage 10w40 oil. I have seen a jump of 10psi in oil pressure. The engine is no longer matching the tach, but running down the road staying between 25-30 psi. At idle it drops below 25-30psi, but staying 10 psi of whatever the tach says. Not sure how long it will last, but definately seeing a difference in oil types giving me better oil pressure.