661s2000

Hey y’all,

I recently acquired an boosted ap1 and after 500 miles noticed some afr issues at idle. The car is in the 10.5/11.2 range while in boost running e85 however I’m still bouncing between 10.7-12.0 afr at idle once the car warms up. I am currently awaiting to get into the tuner to get my issue resolved and in the mean time I decided to pull the plugs.

upon pulling the coil packs I noticed cylinder 2 had some rust inside of the tube, cylinders 3 and 4 had loose plugs and quite a bit of oil inside. This makes sense because I noticed a slight build up of oil on the exhaust side coming from the valve cover. A new valve cover gasket and spark tube seal kit will be here tomorrow and I’ll change those once I receive the parts.

Since I had already removed the plugs I decided to go ahead a perform a compression test. The motor was dead cold however I did perform the test at WOT. The results are as follows:

Cylinder 1 = 205
Cylinder 2 = 185
Cylinder 3 = 200
Cylinder 4 = 200

I plan to do a leak down test in the morning before I put this thing back together but I am curious on opinions here. Do you think it could be a valve issue? 98% of the driving of this car is on vacuum but when it does see boost it’s 13.5psi. I’m a little concerned with it being rings or even worse cylinder wash due to the super rich idle afr. I’m new to boosted cars and e85 all together. I know the topic of e85 and afr has been covered a million times so I won’t go there as I believe every engine is truly different but there is no doubt mine is idling very rich.

please provide some input and I will report back with leak down results tomorrow afternoon.

thanks.

Slowcrash_101

Check the valve clearance on cylinder 2, that may be why it's a little low.

Boosted cars require a different driving technique than NA cars. No engine lugging, more frequent oil changes, etc.

661s2000

Thank you sir, I just got the valve cover off. Going to look into valve clearance and also perform the leak down. I will post results once I’m finished. I’m not sure how to check the valve clearance so I’ll be turning to google haha.

661s2000

Ok so the leak down matched the compression test obviously.

Compression results by cylinder:
1=205
2=185
3=200
4=200
Leak down test:
1=97% - slight leak from turbo outlet
2=78% - major leak from turbo outlet
3=90% - slight leak from turbo outlet
4=94% - slight leak on the intake side

this test was done with a cold engine as I have the head off already. The valves seem to be out of adjustment on cylinder 2 with a feeler gauge being slightly tight or sticky at .080”

Do you think adjusting this valve will bring it closer in tolerance? I’m nervous as I’ve never done a valve job before. TIA

661s2000

*vakve cover off, not head lol*

Slowcrash_101

If the valves are too tight, they won't fully close. .008" on the exhaust side is very bad. Minimum spec is .010" This has a lot of negative consequences, one is reduced compression and increased valve leakage. 2 the valves not seating means the valve seat isn't radiating the heat of the valve to the cylinder head. It stays in the valve and the valve guide. Valve guides are a soft metal as is, if you overheat the guides they will loosen developing play destroying the valve seat over time because the valve begins wobbling with the loose guide.
3 you torch the valve and damage it that way.

Setting the valve clearance is straightforward, it's the distance from the rocker to the valve stem tip, with the cam NOT acting on the rocker.

661s2000

I went ahead and adjusted those valves to .011” and the leak down remaining the same. The air passing sounds like it’s coming from inside the head itself leaning me toward a ring issue.

now I have to make a decision on where to from here. I don’t have anyone in town that I trust to make any assumptions let alone work on my baby. It may be going to Laskey Racing and I can just go ahead and sleeve it and get a fresh build so I’m not worrying and can actually enjoy the car. It currently has 95k miles. I’m torn on what to do.

Slowcrash_101

I can almost guarantee it's a burned exhaust valve. Take off the exhaust manifold and look at the exhaust valve. If it's white it's burned. I would definitely boroscope the cylinder because if you don't have any bore wear I would breathe a sigh of relief as you can just swap in a good cylinder head and you'll be good as new. Much cheaper and more reliable than sleeving.

F1TwoThousand

I highly suggest investigating where exactly the leak is coming from. Id suggest taking off the header first it probably is a burned exhaust valv(intake valves dont suffer same heat cycles). I would not waste anymore time effort or money than to simply upgrade valves and might aswell springs(cheap anyway).


You can see how obvious it will be to find the leak if it is a leaky valve

661s2000

That seems like a great starting point...I’m getting an exhaust gasket coming my way and will pull the turbo and manifold off and take a look. I also ordered a bore scope and will do what I can to post pictures. I appreciate the help and feedback...my thought was honestly that the bottom end was hurt.

I am hoping to have some time next weekend to get this little chore completed with Easter it may be another weekend but none the less I will post my results once I have them.