Thanks for the analysis Jim.
I checked the compression tester on my compressor. reads the same as my compressor gauge.
Would it be reasonable to assume that the rings on all cylinders are just equally worn and the blow bye as just too much for the PCV system to deal with?
It does not burn any oil or smoke and both cylinder banks are low compression. I have not yet pressure tested the coolant system.
Considering its a numbers matching car, my instinct is to just do a basic stock rebuild reusing all the hard parts I can.
Any opinions on using modern internals (roller cam, forged internals, etc.) on a car like that? I've read different opinions on the effect on value.
Well, at 60 PSI, and you know the gauge is correct, I'd say the rings are shot, but it should be burning oil.
You are not at a high altitude like Denver, by chance? Higher altitudes can effect cylinder pressures as well, so it could be OK if you were at altitude.
If it were me, based on the mileage, and knowing it is a numbers matching engine, if money allows I would indeed rebuild it just to know its condition and know it will last another 95,000 miles. Keeping all receipts and taking photos of the engine build (before, during, & after) to document all that is done to it will help keep its selling price up should you decide to sell the car at any time in the future (or even for insurance purposes).
Building the engine depends on what you are looking to get out of it. I would replace the cast connecting rods with forged steel as they are cheap insurance and much stronger then stock. The forged I-beam rods like factory are your first choice and most inexpensive. Then you get into the H-beam which is slightly higher and more rugged - but not really needed if going with a stock or even slightly modified engine.
Depending on bore size determined by your machine shop, you may want to get a dished piston to lower your factory 10.5 compression closer to 9.0 - 9.3 so you can use pump gas. You will lose a little HP, BUT, if you are OK with a few more cubic inches, I would go with a Butler rotating assembly for the 389 which will get you a set of Ross forged pistons dished to match the 72-75 valve chamber cc's of the #77
389 heads to get you at the 9.0-9.3 compression ratio. The additional cubic inches will more than compensate for the lower compression and give you more Torque at the wheels. https://butlerperformance.com/i-2459...tegory:1234862
You are going to need everything in the kit anyway, except for the crank, which you are most likely going to have to get turned$. You can price individually forged pistons, forged rods, rings & bearings and then compare. Balancing is typically $200-$250 which Butler includes. Note that you will need a "neutral balance" harmonic balancer and flywheel according to the website. The factory balances the engine "externally" which uses the harmonic balancer & flywheel to get this done. So you will need a new harmonic balancer and neutral balance flywheel if a 4-speed. Butler can also help you sort this out if you need more info on parts and costs.
Budget is the key here and a Pontiac engine is not inexpensive to build - nor are machine shops inexpensive on their services. The more you can do in assembling the engine, the more you will save.
Roller cams/lifters in my book are a luxury at the prices they get, but can also be a plus when it comes to wear and even a little extra power. The average flat tappet factory style cam in my opinion is just fine as long as you correctly break it in nor use excessive spring pressures and a super high lift number. Heads won't flow much over .470" in stock form, so keeping lift under this number should be no problem with a flat tappet cam. Many choices from stock to street/strip.
For timing chain/gears I like a double roller set-up. Summit or Jegs can be a good source for quality brand parts and they ship free over $100. I have gotten many parts from Summit and have no complaints with them.
I would recommend purchasing the book by Rocky Rotella, How To Rebuild Pontiac V8's
. This will give you a really good step-by-step view of what it takes to disassemble and rebuild a Pontiac engine. Very easy read with a ton of photos that walks you through the process. You can see what parts will need replacing and this can help you write a list of parts you will need in order to generate an expense sheet or enable you to ask questions on parts needing replacement.
So this is just the tip of the iceberg and a few pointers if you decide to go ahead and do a rebuild. You can keep the engine as close to stock if that is the route you want to go or make some modifications to improve/enhance the engine and keep the engine streetable & dependable without going crazy on horsepower.