In our last post, we mentioned the car wasn’t running right beginning in the second road course session. Once we got home and had some time, we compression checked the engine and got a nasty surprise.
Yes, positive evidence of a blown head gasket.
Unfortunately, I put ARP head studs in this engine. That means because of the heater and A/C box the passenger side, I can’t remove that head with the engine in the car, so out it had to come. Thankfully, I had help.
With the engine on the stand, it was a few hours of work and we had found the damage. I had lifted the heads and blown both head gaskets.
Some further investigation revealed no further damage. The gaskets provided a valuable feature as a safety valve and blew instead of allowing damage further down in the engine.
Then comes the really lucky thing: I live in Louisville, Kentucky. Boost Crew Motorsports is also in Louisville, just a few miles from my house. They had every gasket I needed to reassemble this engine in stock. No shipping, no waiting, no problem. Suck it, COVID. If you need Buick parts, hit their website, or give them a call. They’ve saved my bacon more times than I have fingers. Highly recommended.
I had the engine back together in about a day. It took me another day to get it back in the engine bay, and several weeks to button it all up.
But with the buttoning came the disappointment. It wouldn’t start. It’d kick over and backfire and die. Then nothing. I verified fuel and spark. Then, as a sanity check. I compression checked it again. Oh dear.
Cylinder 5 was just 110 psi. Cylinder 2 was 0. My stomach sank. I’d screwed something up, badly.
I took a break to eat something, then came out side. I removed the valve covers and cranked the engine around until #2’s valves should have been closed, and put compressed air to the cylinder via the spark plug hole.
Boom. Air was escaping via a supposedly closed exhaust valve. Did this mean damaged valve? I couldn’t be. #2 had the highest compression of any of my cylinders before I took it apart. There’s no way the head was damaged.
Then I remembered. I put two 8.050″ pushrods in this engine to shut up a couple of the intake rockers. The rockers on this engine are stamped, and I think some variation in build quality left two of them a little noisey. A 0.050″ longer pushrod solve the issue.
I took the rocker shaft off and sure enough, I had put the extra length rod back on the exhaust valve, it was holding the valve open. Doh!
Same thing on with cylinder 5.
Once I swapped those back to the right positions, the compression check cam out like this:
This was a giant relief. It still wouldn’t start, but it built great oil pressure on the starter, so I went to bed frustrated, but hopeful.
The next morning, I removed the intercooler and re-timed the engine. Turns out I had installed the camshaft position sensor 180 degrees out. Oops. I fixed that, and it started… then immediately died.
I swapped out my brand-new cam postion sensor cap for the weathered old one, and the car fired right up. I’ll be in contact with the cap maker to see what’s up with that.
But! There’s more!
I have a new catalytic converter!
This is a Flowmaster high flow racing unit. Probably not legal in California, but it’s good everywhere else. I did have to make an adapter to mate it to the ATR exhaust:
The outlet of the converter was 3″. The inlet to the cat-back exhaust is a 4×3″ oval. So, some fabrication was necessary.
The welds are ugly, but it fit.
I also re-wired the ECM in the footwell, and labelled all the wires. If I get hit by a bus, it will now be possible for somebody else to maintain this car.
Though in the re-wire, the PiDash doesn’t work. That’s on the to-do list. It’s just not getting power. I ripped a lot of crap out of the under-dash area. 20 years hackery is gone.
So, stay tuned. We’ll get the PiDash fixed, get the hood back on, and go for a ride. Then there’s some new stuff going on for the new year. That should get us to the end of January, when the pistons for the Probe should be here and we can start moving on that car.
Thanks for reading!