Compression = 30psi.

[b00stedtalon2]

Did a compression test today, all 4 cylinders have 30psi of compression. Head and block are both resurfaced with a new cometic headgasket with arp's. Block is rebuilt of 1,000 miles ago and had zero problems and head is freshly rebuilt with 0 miles. The motor is also properly timed. Wtf?

I also have no way of doing a leak down test, so has anyone seen such low compression before? Any idea's?

 

[68442]

I'd throw a cap of oil in each cyclinder and rule out the rings. I suspect something in the valves though.

 

[3slow]

Is the gauge itself questionable? How does it run/drive?

 

[delta448]

Was this a wet test or dry?
Was the head pressure tested before installation?
Are the valve lifters shimmed or height-modified?
Are the cams stock?
Were the studs torqued in proper sequence from center outward as outlined in the FSM?

 

[b00stedtalon2]

Was this a wet test or dry?
Was the head pressure tested before installation?
Are the valve lifters shimmed or height-modified?
Are the cams stock?
Were the studs torqued in proper sequence from center outward as outlined in the FSM?

The gauge is brand new, I doubt its questionable. It does not run or drive. Just cranks and cranks like any other car but won't fire up.

I wet and dry tested it. It stayed the same PSI.
I am not sure if the head was pressure tested, I will find out.
Also not sure about the next question, I will find out as well.
Cams are stock.
Yes the studs were torqued in proper sequence.

 

[Rob10_99]

Have you turned the crank over and over to make sure the belts correct? (not to be obnoxios I saw you said it was timed).
Does the 30psi leak down much at all if you let it sit?

You wouldn't happen to be running a 4g63 crank in a 4g64 blcok with 150mm rods would ya?

 

[Rob10_99]

BTW, take off the valve cover and make sure the valves close all the way.

 

[absolute_DSM]

BTW, take off the valve cover and make sure the valves close all the way.

That brings up a good point. How did you time the car? Def sounds like a valve issue.

 

[b00stedtalon2]

Have you turned the crank over and over to make sure the belts correct? (not to be obnoxios I saw you said it was timed).
Does the 30psi leak down much at all if you let it sit?

You wouldn't happen to be running a 4g63 crank in a 4g64 blcok with 150mm rods would ya?

Yes I turned the crank over, all the belts are good. Which is only 1 other than timing belt. The 30 psi doesn't leak at all either. It stayed for a few minutes until I decided to let out the pressure. And no, I am running a straight 4g63.

 

[b00stedtalon2]

BTW, take off the valve cover and make sure the valves close all the way.

Yeah I had installed some stock cam shafts not too long ago. All the valves were definitely shut.

That brings up a good point. How did you time the car? Def sounds like a valve issue.

First I lined up the cam gears then put the belt around them and clamped the belt to the gears. The marks lined up with the surface of the head with both dowel pins facing up. Then I lined up the crank and balance shaft thing although I didn't really need to because it doesn't have any. I then slid the belt over the crank and b-shaft. Then I moved the tensioner bearing up which made the belt tighter and then tightened the 14mm bolt for it. After tightened that, I released the pin for the hydraulic tensioner. Lastly cranked the car by hand 6 times to verify everything is still aligned and belt was tight, which it is. Trust me, timing is dead on.

 

[silver bullit]

BTW, take off the valve cover and make sure the valves close all the way.

This is a easy way to tell all you have to do is check and see if any of the valves are not closing.

 

[absolute_DSM]

First I lined up the cam gears then put the belt around them and clamped the belt to the gears. The marks lined up with the surface of the head with both dowel pins facing up. Then I lined up the crank and balance shaft thing although I didn't really need to because it doesn't have any. I then slid the belt over the crank and b-shaft. Then I moved the tensioner bearing up which made the belt tighter and then tightened the 14mm bolt for it. After tightened that, I released the pin for the hydraulic tensioner. Lastly cranked the car by hand 6 times to verify everything is still aligned and belt was tight, which it is. Trust me, timing is dead on.

Good, at least you know what youre doing.
http://www.dsmtuners.com/forums/art...l-installing-timing-timing-belt-6bolt-2g.html

 

[delta448]

I wet and dry tested it. It stayed the same PSI.

The problem is definitely in the head then.

The 30 psi doesn't leak at all either. It stayed for a few minutes until I decided to let out the pressure.

Not a problem with valves seating if the pressure holds.

I am not sure if the head was pressure tested, I will find out.

Not necessary if your above statement is accurate.

 

[silver bullit]

Are you sure you are opening the throttle wot when you crank the motor for the test?

 

[absolute_DSM]

delta, youre right on with what Im thinking. A valve issue can hold a low amount like this.


And yes he played with the pedal with no change in results. (talking on AIM)

 

[b00stedtalon2]

Are you sure you are opening the throttle wot when you crank the motor for the test?

Yeah, I did one test with no pedal and the other at WOT. Didn't show any difference though.

 

[delta448]

When the head was rebuilt were the camshafts or the cam gears removed?

 

[b00stedtalon2]

When the head was rebuilt were the camshafts or the cam gears removed?

Yeah both were removed for rebuild... Then put back in.

And to answer a previous question, they are hydraulic lifters so there is no lash to adjust.

 

[delta448]

And to answer a previous question, they are hydraulic lifters so there is no lash to adjust.

Correct. They need nothing other than oil.

Yeah both were removed for rebuild... Then put back in.

Any chance that the sticks got switched, swapped or misaligned? -I'm sure you know the intake has the slit for the CAS.

 

[b00stedtalon2]

Correct. They need nothing other than oil.


Any chance that the sticks got switched or misaligned? -I'm sure you know the intake has the slit for the CAS.

Yeah they weren't switched. I doubled checked. They aren't misaligned either.

Maybe its about time I pull the head off and see whats cookin'? Was hoping I could figure out what was up before I do that but oh well.

 

[absolute_DSM]

Basics....

The problems can be -
Head Gasket - improper torque or bad deck/mill
Valves - improper timing or bad lap/valve job
Rings - not seated
Spark plug - bad threads

 

[b00stedtalon2]

^Yup. Well, I'm pulling the head probably some time tomorrow or Monday. I'll post pictures If I find anything odd. Thanks for all the input guys

 

[delta448]

Head Gasket - improper torque or bad deck/mill

Possibly, but I doubt it since compression was exactly the same in all cylinders.

Valves - improper timing or bad lap/valve job

This one gets my vote, the most likely explanation is that something in the valvetrain is amiss that effects all 4 cylinders, -the mechanical timing specifically-. The valves hold pressure, so I doubt it is the valve job. I don't at all doubt his ability to properly install the t-belt, but everyone is human.

Rings - not seated

Not likely, since the compression didn't raise when he wet the cylinders with oil.

Spark plug - bad threads

I thought of this also, but I think the OP is intelligent enough to know if the gauge isn't threading into the cylinder properly.

 

[b00stedtalon2]

I wish it was the timing. I looked over the belt, the cam gear marks are right at the cylinder head surface, and the crank is lined up dead on. I even counted timing belt teeth and got 39 like I am supposed to.

Picture from blcknspo0ln's timing belt install thread.

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[b00stedtalon2]

I didn't have a chance to pull the head today but I went back and did another compression test with all the spark plugs out.

From left to right is 53 - 45 - 35 - 50. I did a wet test on cylinder #1 and got 70.