low compression in all cylinders!!!!!

[g35build]

I have a g35 motor I've been putting together, its still out but starter and flywheel is hooked up for me to check compression. I checked the rings they dont leak, it has new head gaskets, i got a valve job so those aren't leaking. i dont have camshafts or timing on so it cant be the timing but i keep getting 30 or 60 psi compression. I have a motor from a fx35 but they are the same to my knowledge, i even tried the original heads from the fx35 and the g35 heads since i have the rev up. Both heads got 30 psi 60 the most. anyone know why?

[Ken@PTUNING]

I have a g35 motor I've been putting together, its still out but starter and flywheel is hooked up for me to check compression. I checked the rings they dont leak, it has new head gaskets, i got a valve job so those aren't leaking. i dont have camshafts or timing on so it cant be the timing but i keep getting 30 or 60 psi compression. I have a motor from a fx35 but they are the same to my knowledge, i even tried the original heads from the fx35 and the g35 heads since i have the rev up. Both heads got 30 psi 60 the most. anyone know why?

Wait, when you say you don't have camshafts or timing, do you mean you've left the camshafts off the motor entirely and are simply spinning the bottom end?

[g35build]

I have a g35 motor I've been putting together, its still out but starter and flywheel is hooked up for me to check compression. I checked the rings they dont leak, it has new head gaskets, i got a valve job so those aren't leaking. i dont have camshafts or timing on so it cant be the timing but i keep getting 30 or 60 psi compression. I have a motor from a fx35 but they are the same to my knowledge, i even tried the original heads from the fx35 and the g35 heads since i have the rev up. Both heads got 30 psi 60 the most. anyone know why?

Wait, when you say you don't have camshafts or timing, do you mean you've left the camshafts off the motor entirely and are simply spinning the bottom end?

yes, only the bottom end is spinning but theres no spark plugs in. so it wont hold the pressure in the other cylinders while i am doing a compression test.

[Ken@PTUNING]

yes, only the bottom end is spinning but theres no spark plugs in. so it wont hold the pressure in the other cylinders while i am doing a compression test.

That's your problem right there. The cylinder you're trying to do your compression test on isn't getting any air to compress because there are no camshafts to open the valves to let air in. Hook up the camshafts and try the test again.

[g35build]

yes, only the bottom end is spinning but theres no spark plugs in. so it wont hold the pressure in the other cylinders while i am doing a compression test.

That's your problem right there. The cylinder you're trying to do your compression test on isn't getting any air to compress because there are no camshafts to open the valves to let air in. Hook up the camshafts and try the test again.

I will try that tomorrow and let you know what happens. Thank you.

[g35build]

yes, only the bottom end is spinning but theres no spark plugs in. so it wont hold the pressure in the other cylinders while i am doing a compression test.

That's your problem right there. The cylinder you're trying to do your compression test on isn't getting any air to compress because there are no camshafts to open the valves to let air in. Hook up the camshafts and try the test again.

I tried it and did timing and everything, i still got low compression around 60 psi. Could i be doing timing wrong? Theres shorts lines and dots ive lined them up with the dots on the gears. Should i be using the short lines or the dots? The short lines are 180 degree from the dots.

[Ken@PTUNING]

Well dang... Have you tried the test with a little oil in the cylinders?

Yes, the dots should be lined up with the chain.

I would consider doing a proper leakdown test instead to figure out where exactly you're losing pressure from. It's a lot more helpful.

[g35build]

Well dang... Have you tried the test with a little oil in the cylinders?

Yes, the dots should be lined up with the chain.

I would consider doing a proper leakdown test instead to figure out where exactly you're losing pressure from. It's a lot more helpful.

I will try the leakdown test and let you know what happens, thank you.

[g35build]

Well dang... Have you tried the test with a little oil in the cylinders?

Yes, the dots should be lined up with the chain.

I would consider doing a proper leakdown test instead to figure out where exactly you're losing pressure from. It's a lot more helpful.

I did the leakage test and they were all leaking pretty bad but i cant find out from where. The valves were leaking a little but not to the point of where it would give it that low of compression.

[Ken@PTUNING]

What was the reference pressure? What was the resultant pressure? I normally pressurize them with 100psi and I consider anything above 80psi to be acceptable and above 90psi to be perfect.

[g35build]

I was getting leakage of 40 % sometimes 30 % on all cylinders and the reference was 100 psi.

[Ken@PTUNING]

Oh wow. That is not good. You say its not leaking much from the valves but it has be going somewhere. What about the crankcase or coolant passages?

[g35build]

Oh wow. That is not good. You say its not leaking much from the valves but it has be going somewhere. What about the crankcase or coolant passages?

I am not sure if its leaking from there, the valves were little leakage. It wasn't leaking from the head gasket either.

[Ken@PTUNING]

If you're saying the only leak is from the valves then that has to be it. Either they're not seating fully or the valves are being kept open by something. It may not seem like much but perceptibly small leaks can actually be quite large. We had a 2JZ in the other week with an eBay intake manifold and it would not hold pressure in a boost leak test because of a few (what I thought) small leaks between the runners and the adapter plate. Those small leaks wouldn't let me idle the car below 4000rpm with the throttle completely closed.

Then again, you said you tried your other cylinder heads with the same results. It has to be escaping from some other place.