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05-31-2007, 10:43 AM
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#1
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Join Date: Sep 2004
Location: Hamilton Square
Posts: 252
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Rebuilt 350 smoking a little at start-up
Looking at a GTA with a rebuilt carb'd 350 and trans (14,000 miles) ... everything in it works perfectly fine in and shifts perfectly.
The only problem that I see is that the car blows a little puff of smoke at start up. My though is that since the car has 14,xxx miles on it, it should NOT be smoking at all. Though, in my past experience, most of the chevys that i've seen smoke just a little at start. When I had my camaro, it did that too and never really had a problem with it. The owner says that it'll just need a new set of valve seals and should be good to go.
Can anybody attest to this? Or have an opinion on this matter?
edit:
also note that the car was sitting for about three months previous to the current owner getting it (he only had it for several months).
Last edited by bokey; 05-31-2007 at 11:52 AM.
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05-31-2007, 03:37 PM
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#2
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Join Date: Sep 2004
Location: Hamilton Square
Posts: 252
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nobody? hmm
...well I'm having the current owner replace the valve seals with umbrella teflon seals; he said that he is 382748932747328974892% sure that that is the problem so we'll see.
Last edited by bokey; 05-31-2007 at 03:38 PM.
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05-31-2007, 03:49 PM
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#3
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Ayatollah of Rock N Rolla / Admin
Join Date: Mar 2006
Location: Parts Unknown
Posts: 12,573
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Did he run a cranking compression test?
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05-31-2007, 05:00 PM
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#4
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11 second club / Moderator
Join Date: Aug 2004
Location: West Berlin, NJ
Posts: 7,148
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I would most likely its the valve seals. maybe they are not pressed down all the way, or not even changed at all when the motor was rebuilt.
__________________
2001 Trans Am WS6 •SLP Loudmouth II •UMI Suspension •12.857 @ 109.57
1996 Trans Am WS6 •Pacesetter Longtubes •Strange 12 Bolt •Spohn Suspension •11.152 @ 123.85
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05-31-2007, 07:04 PM
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#5
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Join Date: Feb 2006
Posts: 1,385
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Quote:
Originally Posted by WildBillyT
Did he run a cranking compression test?
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hey doing a compression test with oil in the cylinders will give you a false high reading -- many years ago the common test for a down cylinder on a flat 6 was a dry test than wet with oil -- the test tells you if it was a leaking valve or a worn rings set witha down cyl -- jz
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05-31-2007, 10:21 PM
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#6
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Join Date: Sep 2004
Location: Hamilton Square
Posts: 252
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Quote:
Originally Posted by johnjzjz
hey doing a compression test with oil in the cylinders will give you a false high reading -- many years ago the common test for a down cylinder on a flat 6 was a dry test than wet with oil -- the test tells you if it was a leaking valve or a worn rings set witha down cyl -- jz
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Yeah, my pops was telling me about that... At any rate, he did do a cranking compression check. He is in the process of replacing the seals now so we'll see if that is the fix.
The car did sit for about 3-6 months without really being driven; that can make the seals go bad. I should find out tomorrow what the deal is.
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05-31-2007, 11:47 PM
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#7
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Join Date: Jan 2006
Location: Hamilton SQ
Posts: 103
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Matt,
Have him use Viton seals, teflon are garbage.
Valve seals get blamed for alot of things that arent their fault.
you want to know the real story, do a leak down test.
Cranking compression is relative and wont tell you if the rings are going away, it will only tell you if you have a dead cylinder.
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06-01-2007, 08:13 AM
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#8
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Join Date: Sep 2004
Location: Hamilton Square
Posts: 252
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...well, we'll find out today if it was in fact the valve seals or not. If the car is still smoking a little on startup, chances are I'm not going to take it. Leak down test would be ideal, but I don't have the tool 
I was on summit the other day and saw Viton seals; never heard of that type of material before. Looked it up, seems like some heavy ****.
I'm sure that if I do take care of the thing the teflon seals should hold up. At least teflon is better then rubber, no?
Last edited by bokey; 06-01-2007 at 08:20 AM.
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06-01-2007, 09:22 AM
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#9
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Sliderule / Moderator
Join Date: Oct 2004
Location: Catawissa PA
Posts: 2,294
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It's probably doesn't, but if it has the computer controller quadrajet carb check the choke vacuum valve and make sure the choke is opening all the way. When they go bad they can stay partially closed so you get a puff of black smoke at start-up. Can also get pulled closed at WOT causig black smoke.
I did valve seals on my 84 only to find the problem remained and it was all caused by the choke. ECM did net set any codes either.
JB
__________________
93Z M6 Black: The 385 Lives! Supercharged, 3-core front mount intercooler, GTP heads, 3:73's, Street twin clutch, Jethot Longtubes, Mufflex 4" catback/spintech, S+W cage, Spohn Suspenion, Yada Yada Yada
1) Build it
2) Race it
3) Break it
4) Repeat!!!
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06-01-2007, 11:25 AM
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#10
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Join Date: Sep 2004
Location: Hamilton Square
Posts: 252
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Just spoke with the owner; replaced the seals and now she doesn't smoke. Going to go there tonight just to make sure and do a final check over...
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06-01-2007, 05:55 PM
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#11
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Join Date: Feb 2006
Posts: 1,385
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i don't want to step on anybody but a leak down test is not a usefully tool for possible valve seal issues -- if you were to see oil blowing up the valve guide during the test its not the seal --- we use all different methods but start up oil almost ( ALMOST ) not always is the Chevy sealing o rings they use - umbrella seals is always a better deal ( BUT ) worn guides are always in the mix -- jz
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06-04-2007, 01:22 PM
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#12
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Join Date: Sep 2004
Location: Hamilton Square
Posts: 252
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valve seals were replaced and resolved the issue.
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