Compression and Leak Down Test Results..

[OneLove]

My compression came out at 155-155-155-155. No big deal its been like that for awhile.

I did a leakdown test (ghetto style without a gauge, just pressurizing the system) and all seemed normal except.... When I pressurized cylinder 2, a significant ammount of air came out of the spark plug hole in cylinder 4. When I rotated the crank one turn, and pressurized cylinder 2, air came out of the number one spark plug hole. I then proceeded to put a spark plug in the number 4 cylinder spark plug hole and no air came out of any spark plug holes when I pressurized cylinder 2. I put my ear up to my air filter though and I heard a very faint sucking noise.

I am guessing I have a bent/burnt intake valve in cylinder 2. What are your thoughts guys? By the way the car runs great ! I think I might have made 345whp with the way the car is now becasue it feels no different than it did than .

Pat

Edit: I triple checked to make sure cylinder 2 was at tdc and it was for sure so that wasnt the problem.

 

[delta448]

Did you make sure that the engine couldn't turn over when you did the leakdown test? How much pressure did you apply to the cylinders?

When you pressurize #2 or #3 at TDC, the engine can turn over, which would cause either piston #1 or #4 to move through it's normal compression stroke.

 

[OneLove]

Yeah I made sure the engine couldnt turn over. I pressured it to 100psi at first. Then uped it to 140psi which was the max my compressor could go to.

 

[OneLove]

Any ideas guys?

 

[mnetwork]

This same exact thing is happening to me, did you figure this out?

 

[delta448]

I might guess what he wrote above, a bad valve on the intake side of #2. However, intake valves usually last longer than the exhaust valves if something is amiss (other than direct valve to piston contact due to float or jumped timing).

Although it could quite easily just be air escaping past the piston rings. His compression numbers were a little on the low side for an 8.5:1 4G63. How healthy is the compression on the cylinder that you're seeing a problem with?

 

[toofast82]

I might guess what he wrote above, a bad valve on the intake side of #2. However, intake valves usually last longer than the exhaust valves if something is amiss (other than direct valve to piston contact due to float or jumped timing).

Although it could quite easily just be air escaping past the piston rings. His compression numbers were a little on the low side for an 8.5:1 4G63. How healthy is the compression on the cylinder that you're seeing a problem with?

I wonder if he did the compression test at wot?
Still good numbers, i'd say, they are all the same too!
Your right, probably a slightly bent valve

 

[mnetwork]

about 175

 

[HIGHPSI4]

When you do a static test you have to ensure the valves in that cylinder are closed. Did you check the timing of the cam gears to make sure it is not off a tooth? I have seen this happen before. Good Luck with it.

 

[mnetwork]

I did a water pump and of course had to retime the motor in the process. Double checked it after I did it.

 

[tsiAWD91x]

if you had a bent valve then your compression check woulnt come out 100% perfect. their is prob error in the test you ran, altho 155 in each cylinder is deff low horrible for 8.5:1. unless your got a different build your 2g pistons should check out to 175-180psi in all.. if your timing was a tooth off you wouldnt have perfect healthy compression...so you prob doing the test wrong if you got 175-180 in all cylinders your good man that is a healthy ass motor for 8.5:1 comp dont worry about that nonsense your doing, no need. you should be doing this is there is a prob with blow by low comp etc ect.