Hey guys I've been boosted ever since my car was at 150k, made 350 whp on a log manifold for about 25k miles. Then I switched over to a ptuning set up and made 387 whp and 265 lbft tq. All on a dynapack.

So about a month ago I did a pull and mid way through I heard a pop/boom sound and suddenly lost power. I thought I just blew off a coupler or something, it felt like I was all motor although my gauge still saw boost. So I babied it home and checked for anything obvious, and did a compression test. Nothing seemed out of the ordinary and compression showed 240 all across warmed up. I drove it a bit more and it sounded like an exhaust leak and I pulled it into the driveway until I had time check it out. Finally had some time to tear it down yesterday and the exhaust port on cylinder #2 is oily. Did a leak down test and cylinders 2 and 3 are leaking about 30%, cylinder 4 was leaking about 5% and cylinder 1 was leaking about 14%. Thinking its most likely valve seals. Will be taking off the head when I get a chance, sometime after midterms
Here are some pictures of how the ports looked, and the set up I had.

 

one of signs of valve seals for sure. any coolant anywhere? looks like you'll have to pull the head for sure.

pull the pan too.

 

This is my brother and i help him with a lot of work on his car.

Again

The car still ran and still hit the full boost at 11 psi but it sounded really loud like there was an exhaust leak. Even it though it was hiting full boost the car was really really slow. Now much faster than a stock non turbo s2000. We checked for exhaust leaks and found non. The car was not smoking or burning and cooolent. We drained the oil and it looked fine with no coolent mixing in it. We did a compression test and all 4 cylinders were at 240 psi. We pulled the manifold/turbo and cylinder 2 was wet and gunked up with oil.

We did a leak down test and cylinder 1&2 were fine but cylinder 3&4 were leaking about 35%. A lot of the air was coming out of the exhaust ports. So i'm guessing the valve seals/guides/valves are bad??

Were going to pull the head later this week or next week when we get some time. So what do you guys think? Head problem or piston ring/block problem?

All in all not bad for a stock f20c with 180,000 miles making close to 400whp.


Also, how the hell do you take off the timing chain from the gear so we can pull the head?

 

If it's losing pressure through the exhaust, the valve and seat would be to blame. Leaking oil from that area about be from the valve stem seals and/or guides. With that mileage, I could see it being all of it. My guess is that you have two (cylinders worth of) bent/burnt exhaust valves.

 

You undo the center hex bolt that holds the sprocket in place. Pull that bolt out and you should be able to lower the sprocket to take the chain off. Be careful not to drop the spacer either in front or behind the sprocket I forget which side.

 

Are you changing only the valve seals?

 

This type of failure is common for f20s. You will want to spend the money and get all new guide inserts, seats, valves, and get it all cleaned along with valve lapping.

Sent from my Samsung Galaxy S4

 

cracked rings could also be a possibility at that mileage the sides of the ring start to wear down the ring gets thinner and can crack from some detonation have seen it in high mileage cbr 900 motors just a thought do a leakdown and listen to where the air is coming from

 

We did a leak down test and the air is coming out of the exhaust ports. This is with the manifold off so we can feel with our fingers the air escaping from the valves.

If it was the pistons rings Shouldent the air go down past the rings, into the block, then up the oil passages and out the valve cover?

 

ok if its coming out the valve you have bent or burnt valves. with a turbo motor you have to make sure the timing isn't too conservative or you will ignite the mixture too late and the combustion process will still be happening as the valves open causing valve train overheating which will cause the valve stem seals to harden and leak. remember the valve release there heat to the valve seat you may want to have an egt probe along with a wideband. I know it sounds backwards but too little timing can cause as much trouble as too much either way that motor has a lot of miles good luck with the repair . post some pics of the bores when you pop the head of curious to see how they look at that mileage