Compression check

[Chief_Wiggum]

I've got a buddy of mine who's going to help me do a compression check on Saturday...I want to make sure I disconnect the right connections to avoid screwing things up/frying the coil pack. As I understand it, I disconnect the two items I'm pointing at in the picture (CAS & coil pack), pull the plugs (duh) and crank with the accelerator matted to shut off the fuel. Does this sound correct? Thanks from one homo to another.

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[Chief_Wiggum]

Dry results - #1 - 140, #2 - 140, #3 - 150, #4 - 155
Wet results - #1 - 170, #2 - 160, #3 - 155, #4 - 170

The big discrepancy is #3 between wet and dry, the others are semi consistent. Any insight? I should say that we did not measure out the small amount of oil we put in the cylinder, so there could be some variance attributed to that.

[Code Monkey]

Specs for the 1.6L are:

Standard 192 psi
Minimum 135 psi
Diff. between cylinders 28 psi

You are just hanging in there.

[Chief_Wiggum]

That's not encouraging. I think I'll redo the compression test now that I know what the numbers should be and do a leak down test. I'm also going to keep driving the piss out of it to include autocross next Sunday!

[Mazdazilla6]

Numbers look fine to me. 192 seems a bit high to me as the comp ratio is 9.4, our speeds are 9.5 are we are only supposed to hit 180psi.

My miata runs on 3.5 cylinders and it's very noticeable but I never have an issue with power delivery, other than it having nothing down low. But I will say this, the B6 doesn't come alive until 5k-ish so keep the revs up. Also there is no rev limiter so you can shift whenever you want, and it's a non interference engine so even if/when the valves float at high rpm it won't blow up the engine.

[Chief_Wiggum]

I picked up a leak down tester today, I hope to hook it up sometime this week and see what it tells me.

[Chief_Wiggum]

So, finally did the leak down test about a month ago, air coming out of oil cap = bad rings. I also went through about 1.5 quarts of oil getting to and from the last autocross event (see below).

09 Nov 14 BSCC Autocross St. Louis - YouTube

09 Nov 14 BSCC Autocross St. Louis - YouTube

short term fix is a 65K mile 1.6 replacement motor. I'll replace the TB/WP before dropping in the car. I picked it up in Chicago while visiting the in-laws for Thanksgiving. The seller had an engine hoist to load it, I had to improvise to unload it...the Mrs wanted it out of her car (don't blame her). I used jack stands to support the ladder, slowly slid the pallet down until i could slide it over to the cart...I can't believe it worked.


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[Code Monkey]

Maybe do a coolant reroute and plug the front thermostat neck while the engine is out?

[Chief_Wiggum]

The reroute was done on the current engine, so I'll be sure to follow that route. Roger on the thermostat neck.

[Chief_Wiggum]

Finally got my replacement motor mounted to an engine stand yesterday and started some preliminary tear down for TB/WP. No bad surprises yet...keeping my fingers crossed. The engine is out of a 92 with an alleged 65K miles on it. Looking through the spark plug holes, the piston tops on this motor are 1000X cleaner than the ones on my current engine. Trying to decide what else I should consider doing maintenance wise since it's easy to work on out of the car.

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[Chief_Wiggum]

Out of an abundance of caution and since I had very little actual information on this engine, I've pulled the head and dropped the pan on my replacement engine. So far, nothing looks terrible.

before:
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after a little cleaning;
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[Chief_Wiggum]

Had a few extra minutes today, decided to clean up the combustion chambers. I'll work #2 & #3 some more.

Before;
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after;
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[SJP0tato]

Originally Posted by Chief_Wiggum Trying to decide what else I should consider doing maintenance wise since it's easy to work on out of the car.

You probably have done most of these, but just incase:
timing belt/water pump/tensioner
new o-ring seal for the heater pipe (comes into the back of the mixing manifold, runs behind the exhaust header)
new cam gear seals
Water plug (if it doesn't get replaced outright by your coolant re-route):
Entire coolant re-route, hopefully it replaces the thermostat & crap back there that sucks x1000 to work on when it's in the car.

Front main seal
Rear main seal
maybe oilpan seal (since it requires removal from the vehicle anyways)
All of the mini heater/vacuum hoses that run in/over/under/around the intake manifold area.
Fuel injector seals (the little kit from rockauto is about the cheapest I've found, BECK/ARNLEY 1580894 is what I bought a few weeks ago for ~$12 shipped for all 4 injectors. Don't lose the fuel rail spacers, they're terrible about falling into the depths of the engine bay. I glued mine in.

I think that's most of the main things.

[Chief_Wiggum]

Haven't posted an update in awhile; just replaced the valve stem seals. The job was very easy using the KD Valve service tools. I went with the Viton seals on the advice of the Miata.net crowd.
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Hope to start reassembly soon. A friend of mine who works at a tool and die place is going to help me plumb the oil pan for the turbo return line; may as well do it now while it's easy.

What's the recommended method for permanently plugging the "cursed water plug"; tap it and screw in a permanent fitting?

[Chief_Wiggum]

back from the grave update. replacement engine together after new valve stems, oil pan tapped for turbo return line, mild head work. Old engine out (my first, had help from good friend), started swapping over some parts off old engine I'll need. Hope to finish that soon, replace throw out bearing on tranny, move it to the newer engine and start the install in the next few days. I've learned an amazing amount about this car in the last 72 hours.
powder coated goodness, worth 10HP