Compression Test questions

[Bonzi Lon]

The crank bolt is 27mm. If you have a 1 1/16" it will fit also.

Bonzi Lon

[LeonV]

Adjust your valves ASAP. Lash gets tighter over time because the valves wear into their seats. You should see a bump in compression across the board, as well as better idle and low RPM running. Tight valves will "burn" (erode).

[Jennys280Z]

Update:

Thanks you guys, you're awesome! :)

I adjusted my valves and the cold idle issue is completely gone. Starting the motor sounds so much calmer and quieter now, almost like a new car. The first time I started the motor after adjustment, I had over 900RPM cold idle that held there throughout. Even though I couldn't warm it up all the way just idling, I checked manifold vacuum and it was already 16.25-16.50 mmHg. I adjusted the idle down to 800RPM and went for a drive. I agree that there's better power in the lower RPM ranges. When I got back from the store I was idling at 900+ RPM again on a fully-warmed motor! I am guessing vacuum is 17mm+ when warmed up so I'm very happy!

Good early call from FastWoman who first spied my lean issues and warned me of the dangers.

The car drove SOOOO perfect except for a couple of hesitations from 4th gear at low RPM the instant I tap the gas. Yes, I'm being hella picky right now I'm thinking one tooth richer mixture might eliminate that completely as well as raise my idle and vacuum even more.

I hear the sewing machine on the top of the engine now, and that's okay

Timing 10 deg BTDC, fuel pressure rock steady. I'm supposed to have full-time vacuum advance but I think the vacuum advance is dysfunctional on my distributor. I need to have it rejuvenated/rebuilt.

Hey Zed, check these two photos out and tell me what you think. Looking great to me! Thanks for the tip to access the crank bolt from the bottom. I used my 3/8" drive click-style torque wrench, a 1/2" adapter and the 27mm hex socket to turn the motor. I wasn't sure how much torque was needed to turn it but I set the wrench for 50lb-ft and that was more than enough. I slowly did two rotations of the crank and got all 12 valves done in that amount of turning. Remote starters are for compression tests, not valve adjustments! Here's the results on my timing chain:

[Jennys280Z]

My biggest recommendation to anyone doing a valve adjustment for the first time, get this tool.

It made the difference between an impossible job (I couldn't muscle the locking nuts loose with a regular wrench! Seriously??) and a highly pleasant job. The breaker bar was so long the handle was up over the fenders, so nothing under the hood could get in the way. Super-easy! Now that I've done them already and don't have bolts tightened by King Kong, I can do them again with just a regular 17mm wrench.

1/2" breaker bar

3/8" adapter

3/8" extension

17 mm crows foot

[siteunseen]

I had to grind the sides of my 17 mm crows foot down quite a bit. Seems like it was hitting up against the next locking nut on #1.

Jenny's happy, we're all happy.

[Captain_Zeros]

I use two different 17mm wrenches when I do my valves, a nice long one that I can tap the end of with a mallet to loosen 'em, and a little short thin jawed 1970s honda motorcycle toolkit wrench that fits in real nicely for adjusting and tightening.

[LeonV]

Excellent!

[FastWoman]

Congrats, Jenny! See, I told you (or at least I told someone who I think might have been you) that it would be a highly pleasant job. The valve train is easily the prettiest working part of the engine, and there's something very satisfying about adjusting it to spec. And that gentle sewing machine sound.... PERFECT! It's how an engine SHOULD sound. (I don't trust those hydraulic lifters!)

FAIW, I never had any trouble adjusting the valves with ordinary hand wrenches. But then again, I don't think I had a gorilla pre-torque them for me. When I first adjusted my valve lash, I found that two of my exhaust valves had NO (.000) clearance. Scary! Fortunately my compression is good, so none of the valves were burnt, even with the lean running.

[Jennys280Z]

Update!

Did a 2nd compression test today (cold motor again) after the valve adjustment and here are the results:

Compression (psi)

Cyl 1: 146

Cyl 2: 134 (144 with a few squirts of oil)

Cyl 3: 153

Cyl 4: 146

Cyl 5: 145

Cyl 6: 141

What to do about #2? Is a gain of 10psi expected/normal after a few squirts of oil on a motor with 140k? Is it likely its compression rises with the others on a warm motor and gets closer to the others? Should I just keep driving it and letting the Sea Foam in the gas keep cleaning things up? Should I try loosening lash on #2 another .0005"?

After the compression test, I adjusted the AFM one tooth richer. Good news is, the occasional hesitation I experienced on last night's drive was gone. Vacuum is now tested at 17-18 mm Hg warmed up. Bad news is, I have some horrible noise coming from the front driver's side (near the AFM or ignition coil). I heard it very loud climbing a hill in 2nd gear on the way out and so I turned around right away and nursed the car back. I thought it might be the motor...maybe cylinder #2 was complaining because of the oil I squirted in...maybe I forgot to do something or pick a tool up off the car....I stopped the car and just revved the engine and I heard the noise but intermittently, it was hit and miss. When I got back, opened the hood and looked in, the AFM front cover had fallen off completely and was just sitting there. I thought it might be vibration and that front cover causing the noise (is there vacuum present around the potentiometer where this cover should be sealed?). Do ignition coils make noises when they start to go bad? Do AFMs rattle if maybe the wheel isn't straight after an adjustment or something?

I'll include a vid clip of the awful noise, I really hope someone can offer wisdom on what it might be! Thanks a million you guys!!!

<embed width="600" height="361" type="application/x-shockwave-flash" allowfullscreen="true" allowscriptaccess="always" wmode="transparent" src="http://static.photobucket.com/player.swf?file=http://vid81.photobucket.com/albums/j219/amiamelodramatist/isis_garden/photos/2013-05-03_zps5eafb148.mp4">

[Zed Head]

If you mean that noise that sounds like popping inside the intake manifold, you might check your valve lash settings again. One of them might have loosened up. It sounds like other engines I've heard with a bad cam lobe (common on small block chevys), but in your case maybe just a valve that's not opening completely because the lock nut has backed off and the pivot screwed itself in. Easy to check.

[Jennys280Z]

Congrats, Jenny! See, I told you (or at least I told someone who I think might have been you) that it would be a highly pleasant job. The valve train is easily the prettiest working part of the engine, and there's something very satisfying about adjusting it to spec. And that gentle sewing machine sound.... PERFECT! It's how an engine SHOULD sound. (I don't trust those hydraulic lifters!)

FAIW, I never had any trouble adjusting the valves with ordinary hand wrenches. But then again, I don't think I had a gorilla pre-torque them for me. When I first adjusted my valve lash, I found that two of my exhaust valves had NO (.000) clearance. Scary! Fortunately my compression is good, so none of the valves were burnt, even with the lean running.

I'm glad you caught yours early before any damage was done. Just like me now too I suppose!

Yep I was the one you told and it turned out just like you said. I was amazed that I didn't even drop a wrench, even when I was holding two in my left hand at the same time while using the feelers with my right. :)

I won't drop any names in public here but I do have a repair invoice done by a Z-shop who wrote that they adjusted my valves and that was over 15 years but less than 2000 miles ago. So if this shop DID adjust my valves, first of all they tightened them up extraordinarily tight. They also installed NGK GR5 V-power spark plugs which are too hot. They have huge projected tips on them that would risk plug-to-piston contact. Plus when valves are so tight like that I would fear the risk could be piston-valve contact! It seems like if they did the work they said they did, they turned my motor into a time bomb. They also adjusted the AFM and scolded me ("don't mess with THAT!" while pointing at the AFM, and they put some red sealer stuff around the front cover to further make the point). Well I've had my share of messing with it since this journey began to be sure, and this one is a new/rebuilt one from MSA. I sold the old one on Ebay for $90. Remember how I once thought there was a circular dent cut on the wheel that I figured was some kind of pre-marking? You guys (you and maybe either cozye or Zed) were right about that too. On closer inspection of that wheel, it had apparently been messed with multiples of times and the indentations were just from the adjuster screw pressing into the plastic! There were little "dents" all over it, I guess from mechanics trying different positions. If this is any indication of how the professionals "fixed" my car, I'm figuring out that I'm much better off doing things myself! Really like 50-75% of the reason I'm doing all this is for education and experience. I want to know my car better. If I get great results in the process, the other 25% is a bonus!

[Jennys280Z]

If you mean that noise that sounds like popping inside the intake manifold, you might check your valve lash settings again. One of them might have loosened up. It sounds like other engines I've heard with a bad cam lobe (common on small block chevys), but in your case maybe just a valve that's not opening completely because the lock nut has backed off and the pivot screwed itself in. Easy to check.

Hi Zed Head!

Uggh I tightened them all well, even went back with the wrench on all 12 nuts one final time to make sure. But if you're right, are you saying that the lash itself has gotten too loose and the valves may be slapping around and not opening very much?