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View Full Version : Blue smoke on steep decents... why?


Rezarf
10-31-2011, 12:51 PM
I ran White Rim this past weekend and noticed when I was on the steep sections heading down, I would get some blue smoke after a few hundred yards.

It was certainly blue smoke.

It doesn't happen when I go up the same angle, just when I go down.

Whats going on? I am assuming oil is getting past a seal somewhere?

RicardoJM
10-31-2011, 12:58 PM
Is your PCV valve at the front (closer to radiator) or rear (closer to firewall) of the side cover? On steep inclines it is possible for oil to make its way to the side cover area and get sucked into the combustion process. All that said, I believe your PCV is is at the rear and so this is not likely what is going on. That is to say, given the placement of your PCV valvle I would expect it would smoke going up a steep incline.

60wag
10-31-2011, 01:04 PM
Worn valve stem seals? Engine braking tends to pull oil in if the seals are loose.

wesintl
10-31-2011, 01:08 PM
old rule of thumb was blue smoke on decel is valve seals. blue on accel is rings

SteveH
10-31-2011, 01:27 PM
Decel is when your engine has the highest vacuum. Unless the crankcase is way overfilled, I'd vote valve stem seals, too.

Beater
10-31-2011, 01:54 PM
what wes said.

Uncle Ben
10-31-2011, 01:57 PM
Yup yup

TIMZTOY
10-31-2011, 06:49 PM
old rule of thumb was blue smoke on decel is valve seals. blue on accel is rings

Diddo

Rezarf
10-31-2011, 09:12 PM
Bummer, I had the head rebuilt by a highly esteemed shop in Iowa about 8 years ago. I can't have THAT many miles on it.

Should I be concerned? Or just keep an eye on it.

I get a slight puff at start up, otherwise it runs pretty darn clean... for a:zilla:

TIMZTOY
10-31-2011, 10:51 PM
did you change your oil ever 3-5 months if it sits alot ? or just at millage intervills ?

try running a thicker oil. or run some "BG M109" followed by "MOA" when you change your oil

RicardoJM
11-01-2011, 06:58 AM
..Should I be concerned? Or just keep an eye on it. ...

Hmm, this is the engine that is going to be pulled to make room for a fuel injected and modern V8. If that is still the case, keep an eye on it and run it:D.

MDH33
11-01-2011, 07:14 AM
Bummer, I had the head rebuilt by a highly esteemed shop in Iowa about 8 years ago. I can't have THAT many miles on it.

Should I be concerned? Or just keep an eye on it.

I get a slight puff at start up, otherwise it runs pretty darn clean... for a:zilla:


My 60 used to to do this and it wasn't worn valve seals, but a stuck, burnt valve. But that was caused by a scored cylinder wall and it smoked most of the time. :hill:

If it's not burning a lot of oil, I wouldn't worry too much about it. How do the plugs look?

Air Randy
11-01-2011, 09:15 AM
Run a compression check on it. Although the most common cause would be valve stem seals, I've also seen bad head gaskets cause this too. If you get a HG leak into an oil passage area and not around the water jacket area, the higher vacuum on decel can suck in a little oil from an area like this. Sometimes this will show up in a compression check where you will have 1 cylinder (or two adjacent cylinders) slightly lower than the rest.

The good news is, if it is just valve guide seals you can replace those without removing the head. Get a fitting to shoot compressed air into the cylinder, remove the rocker arms, use the SST made to compress the valve springs, remove old seal, install new seal, re-assemble, done. Its an easy afternoon type job if you have the tools

TIMZTOY
11-01-2011, 09:28 AM
leak down test would also good idea if your digging in

Rezarf
11-01-2011, 09:00 PM
Thats some great ideas guys.

I haven't been too concerned. Maybe I will get motivated soon ;)

Rzeppa
11-02-2011, 11:26 AM
use the SST made to compress the valve springs

My spring compressor reaches all the way around the head and presses on the valve itself on the combustion chamber side. It looks just like the one in the FSM. I am trying to picture how to do that with a chebbie style spring compressor (I had bought one and it wouldn't work for the F style head).

AxleIke
11-02-2011, 01:26 PM
I don't know where you all are getting your information, but this is a clear case of a bad LS-7. Last time I checked under your hood drew, you didn't have one. That is your problem.

:D

Uncle Ben
11-02-2011, 03:22 PM
My spring compressor reaches all the way around the head and presses on the valve itself on the combustion chamber side. It looks just like the one in the FSM. I am trying to picture how to do that with a chebbie style spring compressor (I had bought one and it wouldn't work for the F style head).

http://76.my/Malaysia/universal-overhead-valve-spring-compressor-78052-1002-09-aaronngu77@111.jpg

wesintl
11-02-2011, 03:24 PM
Like most things on an F or 2F engine... I wouldn't worry about it unless you can't drive it ;)

Uncle Ben
11-02-2011, 03:32 PM
Like most things on an F or 2F engine... I wouldn't worry about it unless you can't drive it ;)

2 strokes make more powa! :thumb: :D

Rezarf
11-04-2011, 08:58 PM
I don't know where you all are getting your information, but this is a clear case of a bad LS-7. Last time I checked under your hood drew, you didn't have one. That is your problem.

:D

:lmao: