The only way I can think this happens and nothing is damaged is:

Your pushrods are WAY too long, collapsing your lifters and holding the valves open, or more likely....

Your valves are bent.

To replace lifters you'd have to pull the heads. If it was my engine, I'd be pulling the heads to make sure the valves aren't damaged. You MIGHT be able to shine a flashlight into the spark plug hole. Look for a shiny eyebrow. But since it's basically new you may not be able to see it if the piston was dinged by the valves

 

Let's see, zero compression in all cylinders and you're hearing air out the bottom end... You did install rings, right?

 

Yes. Short block was professionally built by shop in Southern California.

 

Zero compression is generally a hole in the piston or bent valve, burnt valve or valves not closing

 

Well if your push rods are to long when you go to torque them down they may be opening the valves ever so slightly causing you to not have pressure in the cylinders.

 

Could be the cam was not degreed correctly

 

That could be it too!

 

Which usually leads to bent valves. I had a smallish cam that was off by 9 degrees on the grind. Advanced. It still fired and actually had REALLY good compression.

Look if your pushrods are being very slightly held open you'll still get compression on a compression test. Unless they're like .100" open. But if they're that far open, they'll hit at tdc anyway.

If it's not the valves bent, and you're getting consistent pushrod length measurements and you think they're just too long, the lifters are collapsed. So either way you're pulling heads

I'm sorry but I think you're going to have to remove the heads and evaluate. There's not much more we can do over the internet.

 

Thanks for the heads up.

 

Quick way to check compression gauge operation put your finger over the spark plug hole have some body turn the engine over if it blows your finger off the hole you have compression! Now to address valves possibly hanging open did you prelude and oil prime the engine! If you didn't your lifters very well could be collapsed! I always pack LS oil pumps with assembly lube and oil bath my lifters for a day or two prior to assembly. As far as cam degree angle it is imperative to do this on LS engines because of the variety of timing sets and the ability to easily put the Crank gear on out of time in the case of some of the sets that are have key way knotches all the way around plus you have adjustable cam gears and advance ground into the cams a lot of the time so you have to pay damn good attention assembling one of these! Also if you are using a leak down that allows you to hook up compressed air and fill the cylinder then getting blow by in the Crank case is understandable especially because your rings haven't been able to seat! But doing a leak down on an engine that has never been fired kinda like pissing in the wind. So follow these steps:

1. Put finger over number one spark plug hole and see if it pushes your finger off.
If not go to step 2

2. Take off all rocker arms set number one down the hole place finger over spark plug hole if finger is pushed off problem is in valvetrain if not it's probably in the shortblock. If it pushes your finger go to step 3.

3. replace rockers leave valve covers off crank engine over until oil reaches all rocker arms. Then back off rockers and crank engine over several more times. Snug down rockers and again finger check number one Cylinder. If still no compression go to step 4.

4. At this point purchase a length checker, remove rockers for number one Cylinder. Measure pushrod length then set tool 0.010 shorter place tool in number one and snug down intake rocker and check for lash the ability to move the push rod up and down if you have no lash rotate the engine watch the rocker open and then close rotate the Crank 1/4 turn from point of closing then recheck lash if no lash note that length back intake off and shorten it again repeat this process until you find the length that gives you lash then go back to the last length and that is the length intake pushrod you need. Repeat these steps on exhaust side and get the right exhaust pushrods make sure you annotate which is which. Once push rod lengths are verified and corrected as needed replace all push rods and rockers spin engine over until oil reaches all rockers. Then repeat step 1. If no compression at this point got to step 5

5. If you are here the problem is in the short block area next is to remove front engine cover and set number one to TDC and. Verify timing marks if timing marks don't line up dot to dot your cam timing is off remove driver side head to degree or if you don't care about doing it right back off your rockers make sure your number one is at TDC and the Crank sprocket dot matches if not mar the tooth that points straight up then match the dot on the cam gear to it so your dots should basically come together with the cam sprocket at 6 and the Crank at 12. If this doesn't resolve the issue then the shortblock needs to come apart.

Hope this helps

 

You said Engine has been Built for a couple years, is it possible what ever assembly lube was used in Cylinder Bores, Gummed up and stuck Rings in Pistons?
Did you Loosen both Rocker Arms on each Cylinder and then blow air in? You can use hose for Compression Tester, just have to remember to remove Schrader Valve in hose. Thats one way to eliminate any bent Valves. It could possibly push piston down at that time so be cautious of that. ( I was replacing Valve seals on a TBI motor and turning Engine over
with long 1/2 Ratchet on the Alternator bolt, you can turn some Engines over that way, and when I plugged Air up, Air pushed Piston down pretty fast and spun Ratchet right upside my Mouth, Hurt like a ****.)

 

Great info, thanks for that. I'm in the process of removing rockers now and the wear pattern of the rollers are dead center of valve stems. I may have tightened rockers too tight. Also, I didn't degree the cam (which i was in the process of buying a degree wheel) because when i called BTR, to specially ask about degreeing the cam or not, they told me that degreeing the cam wasn't necessary and to just line up the dots.

 

ouch!!!

 

Update: I put finger in #1 cylinder and had no compression when turning engine. I then removed all rockers, turned engine over and my finger was blown out of #1 cylinder with quite a bit of pressure. I then re-installed rockers accordingly and noticed that the exhaust rockers were compressing the spring quite a bit while torqueing to 22ft pounds. I also noticed that the finger blowing compression was diminishing and that the engine became harder and harder to turn after each rocker was installed. With only 5 rockers installed, the compression was gone and engine has become almost impossible to turn on certain strokes.

 

Well quit trying to turn it over until you figure out if you bent any valves then get the correct pushrods

 

what is the length (should be on the pushrods) ?

 

stock is 7.385

 

They are 7.600. When i used the pushrod checker, i got the same result every time. Even when i removed them the marks were still dead center.

 

7.600 is tall deck heads and short travel lifter territory. With your set up you should be in the 7.4 range.

That would indicate your lifters are fully collapsed to me.

 

I thought stock was 7.40?