Project Car SOTU: Justy Little Compression Test

It’s been about 2.5 years since I first tested compression on my Justy project car’s three cylinders. That was when I found out it was running on only two of them. Adjusting the valves made it a little better, but it still needed not only a valve job, but a full rebuild. Now that the (finally) rebuilt engine has more than 3,000 miles on it, I thought I’d check compression again.

If you recall, I had my machine shop port the head, and mill the head and block for an increased compression ratio. I also had a Honda motorcycle header modified to fit. I haven’t yet taken this car to the dyno, but it should make significantly more than 46 hp to the wheels. I’m hoping for 55, but that’s probably fantasy land. I’d say it feels quick, but the engine’s better at making noise than horsepower.
One thing I noticed while setting up for this compression test is that the motorcycle exhaust flanges don’t mate perfectly to the head. There’s a bit of an exhaust leak, which I will someday try to remedy with some red silicone gasket sealant.
The black soot in the area also suggests to me that this car runs a fair bit rich. Too rich? I don’t know, but the side-dump exhaust loves to pop and bark on overrun. Maybe that’s just the way they are. That certainly would help explain its poor fuel mileage : EPA ratings and my observed mileage are both in the mid-20s. Not exactly Geo Metro numbers.
So. How did the compression score?

Numbers like this fill me up with satisfaction. They also serve as a reminder that I should probably continue running higher octane fuel in it. It’s well above the upper end spec in the Subaru service manual.

I ran this last test with the engine warmed up, and jotted it on my garage whiteboard next to my previous numbers and the car’s to-do list. The first row of “after” was before I ever started the engine, so it makes sense that the rings seal better now that they’re seated in the cylinder bores. This chart is also my regular reminder of how far this car has come, and that all this work was worth it.

Other things it currently does, that make me less happy:

  1. Leaks oil. Maybe oil pan, maybe rear main seal. I have a new oil pan gasket on hand, so I’m hoping that’ll do it.
  2. Is loud. I love the side-dump exhaust (ahead of the passenger-side rear tire), but I really should get a proper muffler on this thing. It’s just too much for any drive longer than about 20 minutes.
  3. Not cool the cabin. I haven’t refilled the A/C system since I cracked it open for the engine rebuild. It was converted to R-134A by a previous owner, so all I need to do is rent a vacuum pump and set of gauges from the local auto parts shop so I can load it up with a fresh can of cool-juice. It barely worked beforehand, but I’m hoping a properly tightened accessory belt and a purge-and-fill will help.
  4. Seems to consume or leak coolant, albeit a very small amount. This will make it hard to find the source of the leak. Should be fine as long as I keep it topped up.

It has multiple other needs, of course, but those are my biggest concerns right now. Major work on the Justy has taken a bit of a back seat since my sister-in-law has started borrowing it as a commuter. This ’86 Toyota MR2 that I bought from a co-worker has taken my attention and temporarily taken over weekend recreation duty. Once the MR2 is fully straightened out (it needed a brake master cylinder and new oil cooler hoses, among other smaller things), I can sell it for a tidy profit.
Maybe then I can refocus on the Justy. Or maybe I’ll have a Mazda RX-8 to build for LeMons. Yes, for real. Yes, legit price. But we’ll see if it materializes.

Oh, you’re perhaps wondering about the free Fiero that I had previously mentioned turning into a LeMons car (in the background in the photo above). That went back to its previous home. It had too many needs and ultimately it wasn’t a car that piqued my interests. Fiero engines are heavy, underpowered and unreliable. That particular engine had spark plugs completely rusted to the cylinder heads, and dammit, I’m done doing engine disassembly.
I also keep telling myself I should reduce my number of project cars, so once I got the MR2, the Fiero had to go. I should focus on the Justy and make time to ride my mountain bike. And yet, somehow, I still ended up shopping for broken RX-8s.
Thankfully, I have an extremely patient wife.
[Photos copyright 2017 Alan Cesar | Hooniverse]

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15 responses to “Project Car SOTU: Justy Little Compression Test”

  1. Rover 1 Avatar
    Rover 1

    “I also keep telling myself I should reduce my number of project cars”
    Yep. Join the club.
    Yet somehow it doesn’t happen.

    1. mdharrell Avatar

      I got rid of a project car shortly before acquiring my most recent project car, so I’m feeling pretty good about maintaining parity.
      For now.

      1. Vairship Avatar

        Did *you* get rid of a project car, or did the person smashing into your car get rid of your project car?

        1. mdharrell Avatar

          I did it myself. The white 96 near the center of this photo is now in the hands of (or, less figuratively, in the barn of) another local SAAB enthusiast.

          1. Vairship Avatar

            Ah, I figured you were referring to “letting go” of the Metro.

      2. Alff Avatar

        A question for you both … where is the line between project car and crappy used car? Is it based on age? Obscurity? Appeal? I’d love to be able to state that I’ve got seven project cars but that feels dishonest. I experience less cognitive dissonance with the statement, “I have two project cars and five shitboxes that fulfill a need for basic transportation.”

        1. mdharrell Avatar

          If it’s in need of significant repair before it can be safely (-ish) driven, it’s a project car. If it’s in need of only minor repair or, hypothetically speaking, no repair, it becomes elevated to the status of crappy used car.
          In the case of that white 96, it had a seized engine when I bought it and still has that same seized engine to this very day, therefore it’s a project car.

  2. nanoop Avatar

    Dumb question about dry vs. wet test: when I test dry first, on a warm engine, and crank a couple of times for each cylinder, will the last test really be as “dry” as the first? Oil pressure under cranking is low, but still bigger than nothing, right? Or am I overthinking it, and the values of my 16-cylinder Bugatti are all reliable?

    1. Alan Cesar Avatar
      Alan Cesar

      I’m not sure, but the wet test might have something to do with the oil getting on top of the top ring, or soaking through the rings in quantities that aren’t usually there. I suppose that’s why a big difference between a wet and dry test would indicate worn rings.

    2. mdharrell Avatar

      Normally I’m a purist in these matters, but if you’re going to play around with a 16-cylinder Bugatti then it’s my understanding that Charles King’s version really does constitute a significant improvement over Ettore’s original design.

      1. nanoop Avatar

        I am not a purist, my question is valid for all 16-cylinder engines.

        1. Rover 1 Avatar
          Rover 1

          I think that, just to be sure, a full tear down, and replacement of worn parts should be done on any 16 cylinder engines. Mechanical wear is obviously a concern due to the high mileage these engines can cover in normal use.These are after all, simple,easily understood mechanical contrivances

          Though, obviously, they can easily be replaced by a SBC.

          1. nanoop Avatar

            I’m used to that kind of question on 944online forums, and can imagine similar on
            “I just bought a Veyron, a real bargain at 1.5MUSD. Now I hear that changing the timing belts is 32kUSD, that’s soo stupid, can’t they engineer something properly? On my Ferrari, I can have the belts changed for one tenth of that! Any tips or tricks to put in an LS7?
            Also, I want to safari it out, is there a roof-rack for it, or a mud flap kit? Tire recommendations?”

    3. Alff Avatar

      A good question, I’ve wondered the same. I suspect that the cylinders last tested do benefit somewhat. However, the numbers have always come up somewhat in a true “wet” test immediately thereafter so I don’t know that the difference is material.

      1. nanoop Avatar

        It’s probably just overthinking, empirical data aka experience seems to answer this one for me.