Low Compression Results (Help Diagnose Please)

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

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.

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.

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

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.

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

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.

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

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.

Its possible your tensioner collapsed and caused the issue.

You said you didn't check the crank timing mark? The crank timing mark is just as important as the cam marks, so I would check it also. You said it idled and ran okay last time it was running, right? If that is the case, the engine should be okay. I would zero the timing, then re-check the compression. If the compression comes back to something reasonable, then the rings/valves/etc are not bent/broken. Quick, cheap way to check current status of engine internals without full disassembly.

I have had more than a few cases of timing belts getting loose. Most recently, I had a freshly built motor act just like yours. Timing belt had come loose and slipped a tooth. After resetting timing marks and re-tensioning the belt, engine had great compression and ran fine. Just sayin'.

Quote:

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Originally Posted by stealthee

Its possible your tensioner collapsed and caused the issue.

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+1, sounds like a bad tensioner.

Quote:

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Originally Posted by BlackSpyderVR4

I know if you start the car it should tighten up the belt, but I just don't like that much play.

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Oh and DO NOT start that car until you fix that belt/tensioner.

Put the crank to TDC, then look at your cam gears.

And like everyone else is saying, reset timing and check compression.

To reset the crank, I just need to remove the plastic shield, wheel, and balancer and I can crank it right? If I have to pull the motor mount, etc, I just don't want to do this in my apartment parking lot. I will fill a lot more confident doing this in my garage once i move in.

Quote:

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Originally Posted by BlackSpyderVR4

To reset the crank, I just need to remove the plastic shield, wheel, and balancer and I can crank it right? If I have to pull the motor mount, etc, I just don't want to do this in my apartment parking lot. I will fill a lot more confident doing this in my garage once i move in.

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Pretty much, but You will most likely need a tensionor just to get it sort of safe to start. If you don't know how to set time or much about it then I don't recommend you doing it in a parking lot. If I had a dollar for every guy that screwed up their 3s timing I'd have a 3sec car.

BTW if you mean "crank it" as in letting the starter turn the engine then NO. God stop! before you destroy poor engine.

You are in TX, plenty of members in the state that can help you or point you to a good shop that can. That would be the direction I would suggest at this point.

By cranking no I was not referring to the starter. Im talking about turning the crank 1 tooth from TDC by hand so I can realign all the timing marks correctly. I know how to reset the timing have done it several times on other cars and pretty sure I did enough research on this car to be able to reset the timing on the VR4. But at this point in the game I should just wait to I move to the new house. I will probably just flatbed the car to the new house. Because Im redoing the 60k service. I know the previous owner redid the water pump, but i just want the peace of mind knowing it was done right. What I could use is help me start compiling a list of things I need for the rebuild.

Pistons:
Rings:
Pins:
Rods:
Bearings:
AC Delete (New Belt):
ABS Delete:
Timing Belt:
Water Pump:
Oil Pump (Maybe???)-
Tensioner:
Wires/Plugs (Good Spark Plug for 450-500WHP??):
Gasekets:
water meth kit:
Head Lift Fix (Should I????)

So Ill be taking suggestions on parts and where to get them. Im in the process of digging all around the online shops. But I do not have near as much time in this platform as you gentlemen.

All the stuff I already have from page 1:

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)

your one hour south of Dynamic Racing in Alamagordo,NM . just take it there and be done with it. Worry free

^----If I wanted to just throw money at the car I would. This is my hobby and I enjoy this, I'm in no rush. I bought this car with the expectation of turning every bolt in it and tearing it apart and rebuilding it how I want. The only things I will not be doing is machining and any transmission work required.

If you are 120k or over do the oil pump. Do yourself a favor, and add up the parts to do the short block, add in the machine work/assembly cost, and compare to a Pampena staged block.

I'm building the engine myself. It will for sure be cheaper. Even with the machining I don't see it approaching 2k, but that is one hell of a deal for everything being installed and balanced. For the stage 2 it seems like that thing should handle a lot more than 500whp though….

He rates those numbers based on day to day usage. Imagine a 500whp DD, not just when you crank it up on the 1/4 mile every now and then.

Quote:

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Originally Posted by CoopKill

If you are 120k or over do the oil pump. Do yourself a favor, and add up the parts to do the short block, add in the machine work/assembly cost, and compare to a Pampena staged block.

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$700 + shipping for pistons
$500 for rods
$200 for wrist pins
$100 for bearing set
$180 machine shop cleaning and boring the block plus polishing the crank.
$65 New OE main bolt set
~$25 for new freeze plugs

~$1750 plus my labor for mine.

This is a build that is the equivalent of his premium parts list plus extras. I believe that if you are capable (tools and knowledge/formal training) of building an engine and honestly don't mind the time involved with the balancing and clearancing, it's a very good experience for the DIYer. The biggest part of the process is the time spent clearancing. Don't short yourself there, be patient and vigilant in finding inaccuracies and take your time to be thorough throughout the process and all should be well.

Jeff

^^ Your machine shop is very inexpensive...

Machine shop price seems about right for cleaning, bore and polish. Add $200 for balancing though.

I guess mine is expensive then, it was around $220 for that work + two jack shaft bearings replaced on my little 4 cylinder. Either way, cheaper than having it built for sure, but measuring everything is on you then. I was ok with that on my engine's loose tolerances and low power, but it gets significantly more important with tighter tolerances and more power. Make sure your measuring equipment is up to snuff.

They didn't balance the crank. Balancing all the components based on weights and then fitting them to the holes where the bigger pistons go in the bigger holes and the smaller pistons go in the smaller holes all while ensuring the rings end gaps are equal across the board was a lengthy process. Nothing in this world is a perfect fit so quite a bit of time was consumed attempting to make it better.

Even adding $200 to this process seems cost effective to the capable DIYer.

Jeff

Going with Pampena's will be a lot cheaper for sure. Because I have so much tools to buy for this engine build (Micrometers, piston ring filer, ring compressor, cherry picker, engine stand, etc). Im expecting to spend at least a grand in tools. I figure I should go ahead and buy them while Im still only 26, I have a feeling my love for cars will not be going away any time soon so should be an investment. In the last 8 years I have already built 4 engines for my cars. I got spoiled using all my dads tools in his 3 car garage throughout my teenage and college years. BTW you guys always replace the freeze plugs for engines when you rebuild them?