Very Low compression

[4dgs6m3]

alright, I just recently rebuilt my VR4, Non turbo Block, Ross 8.5:1 pistons .020 over, Scat rods and all work by a local machine shop, I ve put about 2000 miles on it, I have had some oil buring issues in the past couple weeks and hard starting on the car, the car would sometimes smoke blue when start up and the go away after driving a few minutes. I thought it was head related, so I proceded to do the valve seals, put it all back together and it ran fine but still burning the blues, the car sat for a few days and the I go to start it and it wouldent start, so I look at the timing and it is off. So i thought I bent a couple of valves, I got a new head yesterday and put it on and made sure it had no bent valves in it, the head came off of a car with 60k on it and never burned any oil so i thought id try that, made sure the timing was good and the proceded to start it and let it run, but it wouldent start. Did a compression test and it was all under 60 Psi across, and also did a leak down test and it had almost 95% leakage in each Cyl. but i listened to the dipstick and I could barely hear anything, I could hear it coming from the intake and exhaust at the same rate, I redid the timing today to make sure it was dead on and I did another compression test today and it reads,

CYL
#1) 45psi
#2) 55psi
#3) 70psi
#4) 80psi

Did a wet test and it read,

CYL
#1) 245Psi
#2) 175psi
#3) 255psi
#4) 225psi

My Question is could it be something other then the rings? Ie, headgasket, Valves , Warped head?

 

[4dgs6m3]

update: I just put all the plugs back in and it fired right up and was runing for a while and smoking most of the smoke went away after runing for about 5min and did a leak down test and found out that at tdc I could hear it leaking through the intake and nothing was coming from the dipstick, but i could fell it coming out of the cyl next to it.


once again im stumped on what this could be,


Any help would be appreciated, Thanks

 

[rc000e]

First of all, you should be doing a leakdown with the motor warm and at tdc in the tested cylinder.

Your numbers are, plain and simple...horrible. The problem is you have so much mixed information, it's hard to rely on the troubleshooting you've done honestly. You said you had leakage here, leakage there, headgasket leakage....it's so much in one.

The facts are, if you did a "wet" test and compression jumped, then the oil is helping to seal the rings, so you've got ring issues. If you've got leakage in adjacent cylinders, you've got headgasket or block issues. If you've got leaking valves, you've got head issues.

My advice to you is, pull it out, and go to someone experienced enough to rebuild the motor properly because assembly practices, component failures, and misplaced troubleshooting could all be responsible.

To elaborate further on my comment on your troubleshooting, I just mean it to the extent, that you make it hard to PINPOINT a problem, but I have no doubt you have major issues.

 

[rhino4]

.
Your numbers are, plain and simple...horrible. QUOTE]


haha little harsh. Hes right tho. You really do have some serious problems.

 

[dsmmike50t]

Horrible numbers, I had a compression test on my old block and had 155 on three off them and 145 on one and the mechanic was suggesting a rebuild. Thats the lowest I have ever heard of somethings seriously wrong.

 

[moto x]

Mine was at 135 across when I started rebuilding mine and I thought that was bad. Good Luck!

 

[Old Mitsu Tech]

Numbers aside, the oil bringing up the compression sure smacks of rings getting old and tired. Valves or head gasket would have not responded to the oil.

Good Job guys.

 

[fourreGsixty3]

Was it every cylinder that you could feel the air comming out the adjacent (sp?) cylinder?

How many times were you cranking each cylinder? I find between 5-8 times per cylinder is perfect. If you only crank #1 cylinder 6 times then crank the rest the same amount of times. Did you instal the ring's stagered? Check your coolant for any possible oil, just to rule out HG failure. Also when doing the leak down test pop the radiator cap off, and watch for bubbles in the coolant system.

Also make sure your TRUELY at TDC. By putting the car in 5th gear, and rocking it back and forth you can slowly move each piston to TDC, and you can use a long screw driver as an indicator (when it just slightly moves back down) also put a piece of rubber on the tip of the screw driver so it doesn't accidently scratch the cylinder walls.

With ring's as the culprit, with such a huge difference in number's that he would have felt a decent amount of air comming from the oil cap hole. I tested a motor with bad ring's that leaked 45%, and you could hear the air whistling out of the oil cap hole.