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Tailpipe always smoking...

turbojose said:
update... so I got the cam carrier off, and inspected all of the valve seals before i removed the springs, and you can see 11 of the 16 valve stem seals riding up high on the valve instead of all the way down where they belong. and after removing the springs, the seals were obviously the wrong ones. they are snug on the valves, but don't stay in place. Damn! i paid a place for a valve job several years ago, and I have been rolling like this for years. thank you all for your help. I'm sure my smoke will be gone once i get all of the seals installed properly.

Untitled by turbojose, on Flickr
Untitled by turbojose, on Flickr
Click to expand...
Look at this nonsense.
 
@turbojose The 16v guide stem seals are pretty tight on the stems, the shop may have not installed them deep enough onto the guides as it can take some force if they are dry and not lubed... and they should be lubed.

Generally the gasket kits will come with two different seal colors, green and red/brown. One is for exhaust, the other for intake.
 
ZVOLV said:
Great. That is cheaper than a turbo!
Click to expand...
So true! Thank you for your help
culberro said:
@turbojose The 16v guide stem seals are pretty tight on the stems, the shop may have not installed them deep enough onto the guides as it can take some force if they are dry and not lubed... and they should be lubed.

Generally the gasket kits will come with two different seal colors, green and red/brown. One is for exhaust, the other for intake.
Click to expand...
thank you for this. I did use an installation tool and a hammer to put the new ones on. However all of the new ones were dark green in color. No contrasting ones for exhaust. Hope that doesn’t cause any more issues.
 
turbojose said:
thank you for this. I did use an installation tool and a hammer to put the new ones on. However all of the new ones were dark green in color. No contrasting ones for exhaust. Hope that doesn’t cause any more issues.
Click to expand...
It's ok, if they were all dark green that means they were most likely viton which is what you want for a stem seal.

If they were black you'd probably have to replace them again in 10 years or so.
 
bobxyz said:
Sure seems like it's pointing to bad valve stem seals. Normally, only the intake valves have seals because only the intake valves are subjected to vacuum that can pull oil past the seal into the combustion chamber. Exhaust valves are mostly under positive pressure.

Intake vacuum is highest on hard decel, and high at idle. Plus there can be some leakage when the engine is stopped with a pool of oil in the head above the valve.

I don't know if there's a simple test for stem seal leakage? Maybe do a leakdown test but crank it around until intake valve is open and block off the throttle body + hoses and listen for a hiss under the oil filler cap?
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Common misconception on the exhaust not pulling oil past the guide due to positive pressure. B20 pushrods engines had stem seals from the factory on intake and exhaust, and 16v engines had seals on all valves from the factory. It's pretty common for 8v SOHC heads to burn oil past the guide in the exhaust even when the stem to guide clearance is in spec. I now run stem seals on both intake and exhaust with SOHC 8v 530/531 heads that I rebuild and haven't had any issues.

And there's actually a negative pressure alone the surface in most ports (Bernoulli principle) and then there are also negative pressure waves which are well below atmospheric pressure.

I had an interesting issue once on a vacuum furnace I was in charge of at work, and the issue was that when flooding the chamber with argon or acetylene there would be oxidization. This slight amount of oxidization in a vacuum furnace can create a ton of issues, mostly foaming or spattering the molten material and contaminating the hot zone and the downstream plumbing. This means about 1-2wk of downtime while the inconel or graphite hot zone is rebuilt and the entire down stream vacuum system is completely disassembled and cleaned.

The issue was a pinhole leak on a fitting for the 3000 psi gas supply line. It would pull in atmospheric air when the chamber was flooded due to the velocity. And that's when I learned that the Bernoulli principle applies even when the internal pressure is 200X the external pressure. Worst carburetor ever.
 
^^^ Thanks, I've been spreading the wrong information for many years. :oops:

Is there any way to check the valve-to-guide clearance without disassembling the head and special tools?
 
bobxyz said:
^^^ Thanks, I've been spreading the wrong information for many years. :oops:

Is there any way to check the valve-to-guide clearance without disassembling the head and special tools?
Click to expand...
No problem.

I use the "wiggle" test when the valve is at full lift to get an idea of stem to guide clearance. When I was working on race 450 moto engines I did the math for max guide clearance when the valve was at full lift (triangle math). You can then use a dial indicator (or a "test" indicator) to measure the wiggle at the valve head. You have to be careful not to add error into your measurement by bending the valve stem. Once you do it a few times, you can be pretty accurate with just wiggling the valve with your hand.
 
Ok... so the saga continues.... thank you all for the help so far. but the smoke is back!

I did do a complete valve stem seal replacement, pictures bellow un assembled.

Untitled by turbojose, on Flickr

Untitled by turbojose, on Flickr

Untitled by turbojose, on Flickr


Got it all back together, fired it up after figuring out some timing issues... I let the car idle for about 20 minutes to burn off some of the oil drips on the exhaust from disassembly. everything seemed normal. there was some very light smoke from the exhaust but i attributed that to burn off from previous. well after the short 20 minute drive on the highway, the car is smoking from the tail pipe again, and developed a slight miss. so i pulled it in the garage and pulled the plugs. this is what I found.

Untitled by turbojose, on Flickr


so just a recap.

1.) checked compression and all cylinders checked out great.
#1 172psi
#2 175psi
#3 175psi
#4 174psi

2. did a leak down test and all checked out great.
#1 3% loss
#2 2% loss
#3 2% loss
#4 2% loss"

3.) found valve stem seals were installed wrong and replaced all 16 seals with new seals with the head still installed.

4.) Listened for air coming out of the water bottle during leak down test listening for possible head gasket leak. nothing there

5.) pulled the down pipe to look at the turbo turbine for soaking... picture above. all looked good there.

my thoughts.

previously, all plugs had a little oil fouling on them but especialy #3 and #4. and now after replacing the seals, #3 is still oil fouled even after only a 20 minute drive. I'm thinking maybe the oil rings on #3 have given out, (but this is a newly built motor with only about 2000 miles on it) or maybe i'm thinking a cracked block? does anyone think that it could be a head gasket on the number three cylinder?

I'm at a loss.
 
Maybe a cracked head around a valve guide, or a cracked valve guide itself, that worsened with the stem steal replacement? I don't know enough about the 16V heads and if cracks are common. The 16V heads are certainly known for bending valves when the timing belt fails. Do you know the history of your head? Has the engine ever not smoked?
 
With the plug being that fouled out I personally have a hard time thinking that it is a valve guide issue unless the guide itself is just about gone. I would personally throw a new plug in that hole and swap injectors around 3->4 and go for another drive. See if the concern jumps, hell if you wanted to you could even swap the coil and wire onto a different cylinder as well. Unless there is so much oil in that cylinder its fudging your compression results you may be overfueling that hole and washing the bore down a little bit.
 
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