Low Compression Results (Help Diagnose Please)

[BlackSpyderVR4]

I took the car to the track about 2 weeks ago and it ran a 13.9 at 3,500FT. Car was running good. Fast forward to a week ago, I was coming off a light accelerated, and hit 10 or so psi. I heard what sounded like a pop and a release of pressure, pulled over checked everything over and car was idling fine, limped it home and noticed it wouldn't boost over 3 or so PSI, no stuttering, no jerking, no smoke, it just felt like it was being powered by a 1.8 4 banger if that. Car pulls 18-20 PSI Vac, and idles 100% fine. I checked all couplers and they all appear to be solid. Decide to do a compression check here are the results (All were on cold engine, was preping the engine to put the upgraded turbos on, but I think I have a bigger problem then what i origninally thought was just a popped coupler):

1-72
2-92
3-89
4-90
5-92
6-87

I had the car hooked up to my Ram 1500 so battery is not the problem. Bought another compression tester….read the same. Manifold was off, so it is not the throttle being open. I cranked it 10+ times. I'm almost 100% i executed the compression test correctly.

I checked the PCV valve-Rattled everything appeared ok. Check timing marks everything was +/- tooth. Put oil in each cylinder, pressure raised by 5-10PSI (cold engine). I have been told if it was bad rings it would increase at least 40 or so PSI. I'm probably going to slap everything together and pressure test on a warm engine. After hours and hours of research all I could find from guys experiencing my same issue on other platforms is either a) did not open throttle during compression check (I have the manifold off, so this is not it) b) Bad rings (but all 6???? at same) c) Valve timing/bent valves (timing marks were dead on). Build list is below:

Aftermarket Parts:
Fuel Loop
3SX Custom Fuel Kit
Tanabe CBE
Aftermarket Boost Gauge
Light Weight Flywheel
Spec Stg 1 Clutch
99 Lifters
DP
EGR Delete
Krank Vents
LC-1 Standalone
T-Case Bracket
Solid Motor mounts (not installed)
Cloned ECU
482 EVO MAF
Mishimoto Performance Radiator w/hoses
550CC Lucas Injectors
Walbro 40 E85 Fuel Pump w/hotwire (not installed)
Dual Core FMIC
Hallman MBC
TB rebuilt by April
S15 Billet Turbos (not installed)

Any help would be greatly appreciated,
Mike

[DocWalt]

Are you saying the timing is on, or just within a tooth? It needs to be dead on to get any meaningful results, and it definitely needs to be warm to get useful results.

[BlackSpyderVR4]

The results were on. All the timing marks were almost dead on, maybe half a tooth off at most. I will run it up on warm engine and see what I get. I have been told even on a cold engine I should be seeing like over 120 easy, so thats why I'm worried a little bit.

[kywhitelightning]

Although the engine does not need to be warm to get good results, Doc is correct; the timing marks need to be exact. Pull the shrader valve out of your compression tester and put the cylinders 1 at a time at TDC and do a leakage test. You'll either feel the air leaking out the intake, exaust, crank case, or it will push out the coolant. I'm guessing you bumped it out of time and simply resetting it will correct it.

Jeff

[stealthee]

You are not going to lose compression in all 6 at the snap of a finger. I agree that it sounds like you jumped a tooth or so.

[Jimvr4]

I would stop messing around and just go ahead with your teardown / build. You're pulling the motor anyway, right?

[BlackSpyderVR4]

I will go back and check timing. I did not realize that it not being so exact could cause such a drop in compression and engine losing the ability to build pressure with turbos.

Jim you are correct I will be pulling the engine. But I really didn't want to rebuild it yet. That is why I'm leaning more towards trying to figure out what this issue is. I don't want to pull engine think I find the problem, put it back in and the issue is the pistons….etc. But I think if the timing is on, then I will have to pull it and tear into it and rebuild.

[kywhitelightning]

It honestly sounds like the crank is off as usually when a cam is off it knocks one bank off not both. Use the crank sprocket for your alignment marks not the pulley. OP is right figure it out and fix it before teardown as it will make rebuilding much more worry free as it is usually a VERY stressful time especially if you do it yourself. Good luck to you.

Jeff

[BlackSpyderVR4]

Ok, so I'm almost 100% you guys were right. I zeroed out the timing marks, from front to back. 0, +1, 0, -1 tooth. So I was like ok, nothing has changed. I then like let me see how loose the belt is. It looked tight so I grabbed the belt by the Intake cam on the front bank and It was loose and in the process it jumped a tooth, so now its 0, +2, 0, -1. It is almost comical how loose it was (I can easily shake it about +1 inch from where it was hanging, I don't know how the engine didn't eat itself, maybe it did. I'm not even going to check the crank, I would imagine it jumped pretty good. I'm going to flatbed it to the new house and pulling the engine. I'm to nervous to redo the tensioner and zero everything out, I don't know if there has been any contact with the valves. I know if you start the car it should tighten up the belt, but I just don't like that much play.

[stealthee]

Its possible your tensioner collapsed and caused the issue.