First off, I want to apologize to anyone that hoped I'd spend the first pages of this blog dedicated to body work. But like Enzo Ferrari once said, "I build engines and attach wheels to them!".
First off, I want to apologize to anyone that hoped I'd spend the first pages of this blog dedicated to body work. But like Enzo Ferrari once said, "I build engines and attach wheels to them!".
On that note, I fell in love with the design of the all-aluminum, 4 cam, 32 valve Cadillac Northstar V8 several years ago. I knew it would cost every bit as much to get a used one built up to snuff as it would to buy a later model crate-engine with everything already done. But tearing into one of these powerplants just seemed like too much fun to pass up so I bought two 1997's, one with all the bells and whistles and 250K kms on it, and a bare bones one on eBay from Ontario that had 100K kms on it (more on that little fib later). Here are the Bobbsey twins:
It wasn’t very long after I got my engines that I ran a few tests on the newer one to make sure there weren’t any bent or broken valvetrain parts. Since there was no obvious grinding, seizing, or blockages after spinning the crank the requisite 720 degrees, a compression test was in the cards to see how well the valves and pistons were sealing. I measured 170 psi plus or minus 5 psi on all eight cylinders, which is right in the ballpark for good static compression on a Northstar. So far so good.
Next up, I cleaned the engine off so that I wouldn’t contaminate the insides with the crud from the outside. I took the valve covers off, and apart from the valvetrain being a little discoloured from hot oil, there was no sludge so that meant the engine probably saw at least semi-regular oil changes. Another thing I learned to look for was a fine metallic deposit built up on the inside of the valve covers in the area of the cam sprockets. I forget what the source of it is, but in any case it’s not a good sign if you have it. Mine didn’t… whew!
What it did have though was worn out exhaust cams. This was my first clue that I’d been “duped” by the eBay seller. 100K kms doesn’t create flat spots on the nose of the cam lobes:
Here's a close up look at the wear:
Closer inspection of the cam followers also revealed that some of them had the tell-tale wear circles in the middle where the case-hardening had worn through to the softer underlying metal. Cha-ching!… I could hear the cash register at the parts store ringing already.
And here’s what the exhaust valves looked like. They're not supposed to have that rough-looking ring around the big end, so they were beyond re-machining for repair. Cha-ching! More cash register bells. Remember, this was supposed to be the low mileage engine. When I removed the valve covers off the high mileage engine, they looked about the same for wear and tear. I probably would’ve replaced most of this stuff on spec anyways since there's really no point in tearing down an engine only to throw the old parts back in it.
At this point I decided to bring the bare cylinder heads to the machine shop for an in depth inspection and rebuild estimate.