I have a 95 talon esi which I boosted with stock motor running at 8psi and had it that way for about 7 years. I finally decided to get the engine built with forged piston and stronger rod etc.
Motor is built and installed it in the car. My first initial start up was good. Used engine break in oil to ran the car, bled the coolant, fans came on and it was good, let it idle for about 1 hour or so and had to shut her down because it was already late.
The next day I drained the break in oil and put in regular 5-30 synthetic oil started the car and it was good and was letting it idle for about 10mins. Then all of a sudden the car starts to sputter and tons of smoke coming out the exhaust (that heavy lingering smoke) so I shut off the car. Let it cool down tried started it up again and the same thing.

I performed a compression test and readings were 30-215-215-215. I put a cap of oil into the cylinder 1 and the pressure went up to 50psi not much of a difference.
So decided to do a leak down test on cylinder 1. I add the pressure to the cylinder and there is no leaks the pressure is holding perfect. Rotate the crank and reset and try the test again and again no leak.
I decided to try the compression test again. This time during the compression test while cranking it wasn't creating much pressure again then i heard a pop sound and the compression went up to 215psi. So i tried the test again and back to 30psi.

I'm really confused here and not sure what the problem is. I'm thinking the problem might be the head and that the exhaust valve isn't seating properly. Forgot to mention that when i pulled out the spark plug it was completely clean and when looking down the plug hole i can see the piston face was clean as well compared to the other plugs and piston faces.

Need some help and hear what you guys think as i don't want to redo the head and its not a head problem.
Sorry for the long story.
Thanks,
Dave.

Did you rotate the engine during your leak down test? Where was the pop noise from?

Plus you never break in an engine by letting it idle. Period. All load.

Pull your valve cover and check your rocker arms and valves, an hour idle time hurts nothing but finds leaks and problems when you get it sorted out take it for a drive as Stephen says and give it some LOAD.

Another vote for pulling the VC and checking for anything visibly wrong.

Did you build the engine or have it built? What was used when building the head 2.0 or 2.4 new/used? Are the valve springs the stock used ones? Any idea what the ring gap is? Piston to wall clearance? Any issues when the valves were lapped?

Bit of an of topic question, what compression pistons did you use?

I pulled off the vc didnt see anything visually damaged. I went as far as removing the hydrulic lifter, rebleeding them and switching cylinder 1 lifters with cylinder 4 to see if anything would change.
I bought the engine built never used. The head is from a 2.0. The the engine has supertech valves and valve springs with pt cruiser lifters, rocker arms and crower stage 1 cams.
No idea what the piston clearence is or ring to wall gap. Wiseco 8.8:1 pistons.

If your VC is still off you can rotate it by hand and check if anything is binding or sticking. What leak down tester are you using?

FAIL.
I would never want that engine after the one hour of idle time. I can't even count how many times I have seen people do this and just completely fail with DSM's all together.

If your putting in a fresh motor, other than maybe a hose clamp being loose, everything else should be good to go.

I actually add oil into my motor on the stand, prime it, check for leaks, then drop it into the car. The cooling system is very simple in a DSM. If you find your engine pissing coolant from everywhere on your fresh motor, shut it off and seek a professional who knows what they are doing Might be a good idea to add the coolant in and check for leaks before you even start it.

Moral of the story is, do not idle your freshly started engine.

I can rotate it by hand and i dont feel any resistance, nothing looks out of place when rotating the crank by hand when comparing to the other valves lifters and rocker arms.
I've put many freshly built motors together and never had a issue from letting them idle. I've never heard that you should never let a freshly built motor idle. Serious
question How would idling it damage it and putting load on it right away won't?

Do a google search on how you should break in a motor and that will give you your answer. You say you have built a few motors, but yet I am surprised that your even asking how idling would damage it and putting load on it right away won't.

Idling the motor is just going to cause the rings to not seat, compression to stay lower, and the motor to burn oil for a long long time.

My current motor was broken in at 35 psi within 20 minutes of the first start. You are only breaking in the rings in the motor. If the motor was built correctly it should be able to go full out race immediately.

Either way if it was me, I would already start pulling that motor out

I would take the car out, put some real boost to it, come back and recheck compression.

Reza how in the world did you get your car tuned in 20 mins and run 35PSI without a Dyno or without being at a track??

And honestly it isn't rocket science to break in a motor just drive it how you normally would and use quality oils. Most of the time the reason if your motor breaks during the break in period it's more then likely crap machine work or the most probable cause is it wasn't assembled right/clearanced properly.

Tuning is like riding a bicycle to me. I don't dyno tune the car ever. It prob takes me 30 minutes to dial in a nice tune on the streets.

My last engine freshening up was due to a seized oil pump at 9k rpm. The car was already dialed in at 35 psi on pump n meth. I didn't have to retune it to break in the new rings.

I know he talks about bike motors but the process is exactly the same...with boost!

Its an absolute MUST READ for anyone who just got their first freshly built motor back from the shop.

Break in secretes

Idling the engine on fresh rings just causes the cylinders to glaze. Which makes it harder for the rings to break in. I am finishing up my 3rd re-ring of 2014 tomorrow. And it will get the same treatment every other one has. It will idle for aslong as it takes me to get it out of the shop then a 50km roadtest, then back in the shop and make sure there are no leaks. Then an idle relearn.

And I don't think on 100's of leak down test I have done I have every seen the gauge read 0% leak down. Have you leak down tested the other cylinders?

Wow! guess I have been lucky didn't know a little idle time glazed cylinders and ruined engines. I stand corrected!

It's not like the engine is going to grenade from idling it. It will still run and sound fine. It just won't be anything special either IMO.

I watched a couple of buddies go through the same thing with Steve Kinnaird's old 1g DSM over the winter. The first rebuilt motor that went into the car sat around idling and just got started over and over again while they tried to figure out little issues.

Well that didn't last too long and the motor was out of the car in no time to get re-ringed (just to blow up again, but that is a different story). These guys are my good friends. I try to preach to them to pound on the motor asap in order to break it in, but even they do not get the concept

Here's some food for thought. A girl here at work used to work in the engine dyno room at the Toyota plant. She told me how she revved up each motor to 10,000 rpm under certain load and control conditions in order to break them in, then they were dropped into the vehicles. Quite the opposite of having it just idle around

Alright I guess now I know and knowing is half the battle. yo joe.

Seem like everyone is agreeing that its the piston rings that is causing the problem.
Going to pull out the engine and get it re-ringed and get the machine shop to give the whole engine another look through to make sure all the clearences are good.