Engine Compression Test Results

I ran a few tests on my motor this evening. The results seem pretty good but I'm not an expert. I posted them on two different internet forums to get a few additional opinions.

Oil Pressure:
At idle (~600RMM), my oil pressure is 40psi when the motor is cold. It drops to 20psi after the engine is fully warmed up. I held it at 2000RPM in neutral and the oil pressure was 40psi.

Vacuum:
My engine vacuum is 17 at idle (~600RPM). It stays about that amount from 8 to 16 degrees advance (based on 40 year old harmonic balancer markings.

Engine Compression:
Let me first detail how I tested compression. I warmed the engine, blocked the fuel line, disconnected the coil, held the thottle wide open, and then had my wife crank the motor over.

The psi continually rose with each crank so I was not sure when to have her stop. I measured it at what looked to be the 6th compression stroke and on the 8th compression stroke. I stopped on the 6th cause it seemed to be enough cranking (in my mind) and at 8 because that was about the max for each.

The results are:
1 - 143 @ 6 / 152 @ 8
2 - 150 @ 6 / 160 @ 8
3 - 145 @ 6 / 150 @ 8
4 - 150 @ 6 / 155 @ 8
5 - 150 @ 6 / 160 @ 8
6 - 150 @ 6 / 160 @ 8
7 - 148 @ 6 / 160 @ 8
8 - 142 @ 6 / 152 @ 8

The shop manual states compression should be between 130 and 170 for a 289. Based on my math, the biggest variance is only 7% which is under the recommended number of 20%.

Spark Plug Appearance (@600 miles)




A little background is I purchased the car 1.5 years ago and have put 1000 miles on it. I've not had any trouble but I've occassionally seen a hint of blue smoke if I start it and then rev it a little before it is completely warm.

When I purchased it, I was told by the 25 year old owner that it was rebuilt before he purchased it from his girlfriends dad. He said the motor was rebuilt 8 years prior. When I asked for mileage since rebuild, he said 160,000. However, he told me he drove the car on weekends only, it had not been inspected in a year, and the odometer read 70,000.

I'm skeptical on the history of the motor but would like to make sure it is ok to work with it as is. I don't have much money but would like to add a 4 barrel intake and a few other parts to make the car a little more fun. If the motor is not up to the task, I'll save the money and just have the motor rebuilt in a year or two.