View Full Version : smoke when i start up

05-24-2007, 05:16 PM
everytime i start the truck i see smoke come out the back and i dont know why...its like a white/grayish color. I just got a new cat converter u think that'll do the trick? I'll find out when i start it in the morning

05-24-2007, 05:17 PM
Valve seals, very common in SBC's prior to '94.

05-25-2007, 10:13 AM
sounds like your burning a little oil.

05-25-2007, 03:44 PM
Yeah, my truck does the exact same thing. What happens is, when your truck sits, the oil just chills in the heads and the valve seals leak a little, so a little bit of oil gets into the cylinder and it burns up when you start it. I'm gonna do a valve job on my truck this summer to fix it, it's not an emergency, but it needs to be done.

05-25-2007, 04:07 PM
yea most likly the valve seals, they go pretty easily over time

05-26-2007, 01:03 PM
could that be the answer to how the truck performs as well? it doesnt have as much power as it used to, thought it was a clogged cat so i fixed it

05-26-2007, 06:44 PM
If the valves are leaking the same as your valve seals then you may need a head job. The best way to check this is a leak down test. Also how long since a through tune up/filter change? I had a 89 2wd I got for parts that the guy said had a worn out motor. A tune up and some other odds and ends later, the truck ran great and I sold it for a good profit.

05-27-2007, 02:16 PM
could that be the answer to how the truck performs as well? it doesnt have as much power as it used to, thought it was a clogged cat so i fixed it

yes because your pistion rings leak so you dont get as good a compresion at tdc and plus the oil is being burned along with your gas. your doesnt sound too but so you might be able to buy some sealer that you add to your oil, i never tried it but sounds like it works

05-29-2007, 12:43 AM
thanks for the help guys i really appreciate it...gettin fixed tomorrow

05-30-2007, 03:27 PM
this is very common with gm motors especially 350s. just the black smoke at start up. every chevy i've had except for a brand new one did this. i had a 94 z28 camaro that started doing it around 70k miles. every ford i have had didn't do it only the chevy's. i'm not making out like this means it is inferior. i never worried about it. it didn't do anything to the performance of the vehicles.

05-31-2007, 04:45 PM
valve seals

05-31-2007, 06:14 PM
yep. valve seals. my 86 camaro did the same thing. I'm not gonna say how much it cost to fix, but it was a healthy amount

06-03-2007, 06:48 PM
lemme know some prices so i can get an idea....

06-03-2007, 08:05 PM
haha i just kept running my camaro, and everything i drove with that problem. it just blew smoke at start up, but thats all. like i said it never interfered with the sufficiency of the vehicle.

06-05-2007, 04:03 PM
you could run it like that for like up to a year maybe more with out any more damage being caused

06-07-2007, 01:53 AM
Seals are cheap, under $20.00 Labor is a bunch, its a pretty big job. I agree, run it...

08-02-2007, 06:34 PM
truck throwing out black smoke on startup, mine does the same thing. i have a sierra 91 model. i also notice like u said that it kind of bogs really badly when i begin to accelerate, even when i punch it. once it's warmed up it runs good but i think it could run a whole lot better. i have new, wires,plugs,oil,oil filter,distributor cap, and fuel filter. any one know wut it could be? sensors? the location of sensors?

08-02-2007, 06:46 PM
you could run it like that for like up to a year maybe more with out any more damage being caused

And where did you come up with that timetable? :whatever:

Leaky valve seals are very common and nothing to stress over. My 90 350 did this and it had 180k miles on it when I sold it. Didnt use any appreciable amount of oil between changes and it smoked at startup if it had sat for a while.

08-02-2007, 07:56 PM
not trying to jack the thread, but i'm pretty sure my 97 does this on start up, and i'm not positive but i think, it may every time i slam the gas pedal down, it doesn't show any noticable smoke at idle, but it also seems like a rich exhaust smell also.

08-02-2007, 11:13 PM
my old Daily driver a 93 mercury cougar XR7 with 150k+ miles had a pretty good valve seal leak, every morning a nice big cloud of smoke would come out, used some CD2 engine stop leak (wasnt going to put money into it) and it stopped smoking and ran a little better after that, drove it for another 6 months and sold it for half what i paid for it (i drove it over a year)


08-06-2007, 11:38 PM
Yeah but I bet them Chevys outlasted them Ferds, even with the oil burn on start up lol.

08-07-2007, 07:07 PM
i inquired at the dealership where i work at, about where to start at fixing this, the service manager told me that unless i wanted to spend a bunch of money in parts right now, if i didn't have anyother issues, to keep driving. he told me these chevy engines will go for years with smoke pouring out the tail pipe.

08-07-2007, 09:42 PM
i would say its your vavle seals too. you may try synthetic oil instead of adding the leak stop stuff

08-07-2007, 11:21 PM
It usually starts to happen when the motor gets to around 70k give or take. on my 86 it happened with the original motor at like 72k. the more miles it went after that the more and thicker the smoke it put out. on my 94 z28 camaro i had it started at 68k. my buddy has a 76 c30 with a 396 in it that had like over 250k miles on it before the crankshaft went. his truck was blowin the black smoke, and idle, and on acceleration it smoked so much haha.my boss 87 chevy van with the 305 smoked like a stack until it finally died at like 230k miles. it smoked for a long time though with no engine problems. i think it's got something to do with the chevy motors. my best friend has a 66 vintage pickup with a 454 that does it too.

08-07-2007, 11:32 PM
i would say its your vavle seals too. you may try synthetic oil instead of adding the leak stop stuff
I use Mobil 1 full synthetic and it still does it so that won't help. I like the idea of using that stop leak stuff, but I don't like the idea of pouring random sh*t in my expensive Mobil 1. I didn't put seafoam in my crankcase for that reason. Maybe i'll throw some in before i'm due for an oil change.
And don't be hatin' on Ford's reliability. My Cobra's got the original 5.0 and Borg-Warner heavy duty T5 with 156K miles, never been into either and it runs 13's all day long. I'm just saying as far as engines go, the Ford 302 is no joke, the Chevy 350 and 262 engines are certainly something to be proud of, as well.