Smoking at idle...getting a little frustrated...need advice - Team Camaro Tech
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post #1 of 31 (permalink) Old Nov 4th, 05, 11:12 PM Thread Starter
 
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Unhappy Smoking at idle...getting a little frustrated...need advice

Ok...Recently rebuilt motor, with new everything, is smoking at at idle. The longer I let it idle the thicker the smoke tends to get. The smoke is blue/grey in color and is most visable in the sunlight or carlights. I have about 100miles on the motor now. The passenger side plugs, all 4, are black and look a little wet/shiny. I cannot tell if the wet is oil or excessive fuel. The driver side plugs are dry and black/brown in color. So this leads me to think that it is not a carb problem because it should be the same on both sides...right? I don't see any smoke when cruising.

Any ideas on what is the primary cause of the smoke and how to correct it? I'm thinking oil is getting past the intake gasket on that side but, I'm not quite ready to go tearing things apart without a second opinion.

Thanks, Jason
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post #2 of 31 (permalink) Old Nov 5th, 05, 04:25 AM
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Re: Smoking at idle...getting a little frustrated...need advice

I would be assuming and hoping valve stem seals.
Do you get smoke on decceleration? (high manifold vacuum)
Perhaps it's possible that one head (passenger) was not reconditioned to the right specs as the other.. Did you install the seals and pehaps cut them on the keeper grooves? Were the valve guides re-lined or anything else that may have created excessive clearance if done wrong?

This could also be the case with excessive piston to bore clearances on the passenger side. A machine shop mistake? It's a long shot, but crap like this can and does happen..

I'd suggest to do a compression test to check for clues. If you have oil on one side, you will get a higher reading so you'll need to squirt some oil in all 8 and crank it over a few times. You may then see a difference in cranking pressure although it may be subtle. If you see no difference (mainly from large ring end gaps), I'd hope to think the bottom end is OK.

The easiest solution would be to replace the valve stem seals.. Just do the passengerside intakes and see if it helps. Are you using stock rubber umbrella types or guide mounted teflon seals? (They are better.)

Another possibilty is poor intake gasket sealing where oil could be pulled from the crank case into the bottom of the ports on one side. If the heads and/or deck was milled, this would create a less than optimum mating of the manifold to the heads. I have never seen it first hand (it could be crap), but have heard of it more than once..
Do you have poor vacuum at idle?

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post #3 of 31 (permalink) Old Nov 5th, 05, 06:27 AM
 
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Re: Smoking at idle...getting a little frustrated...need advice

I'm thinking valve seals also. I had an expensive rebuild done once, and the builder did not replace the valve seals because he said that the teflon seals still looked good. After the rebuild, which included an R&R of all of the valves,mine would belch the same smoke at idle you describe. I then read an article that said once the valve is removed from the head, the seals are easy to damage, and should be replaced. Bottom line, if the seals were not replaced, but the valves were removed, there is a good chance the they were cut slightly by the valve stem on the way in, causing a small oil leak into the chambers. It sounds like oil, not gas or water. The only two places it can originate are the valve seals or through blowby of the rings. Run a compression check to narrow it down, but IMO, its probably the seals.
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post #4 of 31 (permalink) Old Nov 5th, 05, 07:08 AM Thread Starter
 
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Re: Smoking at idle...getting a little frustrated...need advice

Steve, There is no smoke on decelleration that I can see. I bought the new heads completely assembled so, everything "should-be" in good shape. I'll do a compression test later today on all 8 cylinders. When I measured the piston clearances before installation they were all within spec. I have not had any vacuum problems.

Bob, It is a little odd to me that the seals on 4 cylinders on the same side are bad when the other side is fine?

Thanks, Jason
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post #5 of 31 (permalink) Old Nov 5th, 05, 08:11 AM
 
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Re: Smoking at idle...getting a little frustrated...need advice

Yes, I thought the same thing, but it'd also be odd if the rings on one bank were not seated, and the other side was. If all four plugs are fouled, then all four cylinders on that bank are getting too much oil somehow. On mine, one side smoked much more than the other as well, though both did smoke some, and the driver's side plugs were a mess by comparison. All it takes is a nick or two in a the seals on a couple of cylinders to cause some smoke.
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post #6 of 31 (permalink) Old Nov 5th, 05, 08:34 AM Thread Starter
 
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Re: Smoking at idle...getting a little frustrated...need advice

I'll try replacing the seals first before taking off the intake. It is entirely possible that the heads were built by different assemblies, one who knew what he/she was doing and one how did not....
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post #7 of 31 (permalink) Old Nov 5th, 05, 09:51 AM
 
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Re: Smoking at idle...getting a little frustrated...need advice

Quote:
Another possibilty is poor intake gasket sealing where oil could be pulled from the crank case into the bottom of the ports on one side. If the heads and/or deck was milled, this would create a less than optimum mating of the manifold to the heads. I have never seen it first hand (it could be crap), but have heard of it more than once..
There is no crap to it. Depending on the amount the heads were milled what gaskets (thickness) was used. The way the intake was torqued, how much the deck has been milled on the block. Anything is possible. This is a fact. I have seen unprofessional work done and the customer have to figure out the issue. Im not saying this is his problem but I have seen the exact same condition and this was the problem.

P.S. The unprofessional shop is no longer in business.
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post #8 of 31 (permalink) Old Nov 6th, 05, 11:59 AM
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Re: Smoking at idle...getting a little frustrated...need advice

This is an issue going on in several posts, including one of mine. Did anyone mention guides? I have been down the road of resealing the intake, including milling, with no luck yet. In my case I think it could be the guides. The engine builder used positive seals and they appear fine on my worst cylinder which is #2. My #4 cylinder is second worst and it is suspicious being next to each other. I'm am about to remove the heads and do the guides, which the builder said were fine.

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post #9 of 31 (permalink) Old Nov 6th, 05, 05:39 PM Thread Starter
 
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Re: Smoking at idle...getting a little frustrated...need advice

Yeah..I read a bunch of the other post and still was lost. Valve guides have been mentioned as a possiblity, but since the guides are new I had not given them much thought. I spent the day over at a buddies how tinkering with the enginer and out final thought is that I need to first replace the intake gasket before tearing into the engine. We also suspect that I have a flooding problem at idle.
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post #10 of 31 (permalink) Old Nov 6th, 05, 07:43 PM
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Re: Smoking at idle...getting a little frustrated...need advice

Quote:
Originally Posted by Gary L
I'm am about to remove the heads and do the guides, which the builder said were fine.
Before removing the heads, you may be able to measure the guides with the head/s in place. please note that I said "MAY".

Obviously you can measure the valve stem, but you may also be able to measure the guide i.d. if you have the right sized bore gauge of course.
You MAY be able to allow the valve to rest on the piston at a depth safe enough to take a measurement. Then, pull the valve back up with a small magnet on the valve tip. (Ever see those telescopes with magnets that pick up hard to reach stuff? They're usually less than 5/16"-3/8" dia.) You will have to remove the stem seal or it will stop the valve coming up out of the guide.

Make sure the valve stem is super clean and the keeper grooves or tips have no burs.

Just a suggestion to hopefully save you pulling the heads.

A clearance of 0.001"-0.002" is considered fine.

Nov 68 Van Nuys. 327 floor-shift-auto, Frost Green and not much else when new.

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post #11 of 31 (permalink) Old Nov 6th, 05, 09:25 PM
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Re: Smoking at idle...getting a little frustrated...need advice

Quote:
Originally Posted by BlackoutSteve
A clearance of 0.001"-0.002" is considered fine.
This the info I need. The service manual says factory tolerance is .001" to .0037" (the high end for service). Does .0037" clearance produce any perceptable mmovement? In other words should I be able to see or feel any movement? If I should not be able to see movement or feel it then the guides are shot because I can see and feel movement. Right now the piston is close to TDC and the valve head is resting on the piston. I should be able to turn the engine by hand to lower the valve enough to make a measurement. Thanks.

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post #12 of 31 (permalink) Old Nov 7th, 05, 03:32 AM
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Re: Smoking at idle...getting a little frustrated...need advice

0.0025"-0.0037" would be an extreme upper limit for any standard engine. And I wouldn't go beyond 0.0025" for any half decent performance engine in my view. -especially one with a high lift/aggressive cam.
I just recently had my heads reconditioned and was going to reline the guides if any were beyond 0.002" so I guess it depends on how fussy you are and the application.

All mine were within 0.001" and 0.0015" and I could still feel movement by wiggling the valve in the guide. (Heads off, and stem tip flush with the top of the guide.) So, you will still feel some movement even with fairly tight clearances.

Loose clearances will wear the guide in an irregular shape, (think of a 1/4" round file in a 3/8" hole), and will allow the valve head to seat inconsistanty and possibly accelerate valve seat wear.

Be extremely careful lowering or raising the valve with the piston. If you let the valve drop in, off comes the head! But also the valve guide is at a different angle to the bore centerline and it may bind with help from the valve relief. I suggest pulling the valve up each time before rotating.

There is a formula to measure guide wear by the amount the stem wiggles in the guide but you need the heads off, and if you had the heads off, I'd just say take them to your machine shop.

Have you been able to take any measurements yet?

Nov 68 Van Nuys. 327 floor-shift-auto, Frost Green and not much else when new.

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Last edited by BlackoutSteve; Nov 7th, 05 at 03:43 AM.
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post #13 of 31 (permalink) Old Nov 7th, 05, 11:07 PM
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Re: Smoking at idle...getting a little frustrated...need advice

Sorry, I should have mentioned it's OK to accept 0.001" extra clearance for the exhausts..

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post #14 of 31 (permalink) Old Nov 8th, 05, 08:39 AM
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Re: Smoking at idle...getting a little frustrated...need advice

No measurements yet Steve. I will try for this week. I really want to get this thing straightened out so I can just go out and enjoy it.

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post #15 of 31 (permalink) Old Nov 8th, 05, 06:58 PM
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Re: Smoking at idle...getting a little frustrated...need advice

would it help to do a leak down test first.

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