Low mileage crate 350HO smokes on start up ?

[ozkiwi]

My 5 year old crate motor has started giving the occasional puff of smoke on start up sometimes.It's a bit random as it does not do it all the time.It just seems to go through stages when it does. It has 15000 miles on it and otherwise runs clean and uses next to no oil.I was thinking the valve stem seals might need replacing as I have heard the have always been a bit suspect in GM crate engines.Has anyone else here had this problem ?

[Bloodhound]

Originally Posted by ozkiwi

My 5 year old crate motor has started giving the occasional puff of smoke on start up sometimes.It's a bit random as it does not do it all the time.It just seems to go through stages when it does. It has 15000 miles on it and otherwise runs clean and uses next to no oil.I was thinking the valve stem seals might need replacing as I have heard the have always been a bit suspect in GM crate engines.Has anyone else here had this problem ?

That would be my guess.

[Dead Parrot]

What color smoke?
General rule: blue = oil, black = rich, white = coolant.

[RADustin]

small block puffs on start up is valve stem seals 99 times out of 100.


Does it smoke everytime or only after its sat more than a few hours?

[mr48chev]

One would first suspect valve guide seals. No more than you drive it and if there is no measurable oil consumption I don't think I would get real excited.

On the other hand are sure it isn't black smoke from when you are starting it? An engine that isn't run that much may be a bit cranky about starting, I know the 454 in my 77 Dualie is. That truck only leaves the yard when it has a job to do because of the bad gas mileage as it has a 10 ft flatbed with a hoist to pack around.

[ozkiwi]

It only does it after sitting for a while and I if I give it some throttle on start up .
I thought it might just be excess fuel from pumping the throttle because it looks more white than blue but the smell of burnt oil is pretty distinctive and it smell like burnt oil.

[ozkiwi]

[QUOTE=mr48chev;8328746]One would first suspect valve guide seals. No more than you drive it and if there is no measurable oil consumption I don't think I would get real excited.

Checked over the last few months and no measurable oil use.Still annoying on a low mileage motor.it is the passenger side bank only.
If you get the piston to TDC on a SBC with vortec heads is the valve going to be held up by the piston?Works fine on Ducati motorcycles to change valve stem seals.

[Palf70Step]

Check you plugs to see what condition they tell you, oil, excess fuel etc. As mentioned already, I would't worry about it too much. I just feel these things are not meant to set. To keep in shape requires regular running.

[Dead Parrot]

2nd the check plugs. Might be one cylinder. If so, add replace valve seals on that one to squawk list. Then don't worry about it until you have the valve cover off on that side for some other reason. There is a tool you can get that uses air pressure to hold the valves up for just such a repair.

Possible seal was bad install or or just bad and not caught at factory.

[Mr_Rich]

The engine I installed in my '89 K1500 EC does this. It was also a roller-cam engine I stored in my garage twenty years. I'd turn the crank every so often during that storage time. It will put out a small puff of blue (oil) smoke on start-up and sometimes a bit bigger puff of smoke on start-up but it's not using much oil until at least 2500 to 3000 mile intervals. I don't think it's worth the time to chase a problem that isn't trouble, especially for my almost thirty year old truck. Installation of that roller-cam engine allowed me to get 20 mpg on long trips multiple times so I can't complain. The flat tappet engine that was my previous engine is the same exact engine block and never got that kind of mileage.

[xrcr]

Only you know how much aggravation you can handle. JMO but oil is still pretty cheap and it sounds like it is negligible consumption

[Mr_Rich]

The only thing I'd really worry about in my situation is if it affects the cat converter and might fail my smog checks. The cat converter is probably fifteen years old now anyway so if it's affected negatively then changing it might come due. So far, so good.

[andyh1956]

What viscosity lube oil are you running?

[ozkiwi]

Stuck a new set of plugs in when I first noticed it and they all looked the same which is center electrode perfect tan color with a bit of black carbon on the rim so cannot detect what cylinder it is.
I guess I will just leave it as seems like I am just being 2 picky.
Still like to know if the valves are held up at TDC on vortec heads if anyone knows?

[Jake Wade]

You need to use a fitting that screws in the spark plug hole and compressed air to hold the valve up. That's one method that I use.

[AussieinNC]

Originally Posted by ozkiwi

Stuck a new set of plugs in when I first noticed it and they all looked the same which is center electrode perfect tan color with a bit of black carbon on the rim so cannot detect what cylinder it is.
I guess I will just leave it as seems like I am just being 2 picky.
Still like to know if the valves are held up at TDC on vortec heads if anyone knows?

If you are asking if the piston at TDC will hold up the valves enough to allow you to change the stem seals, the answer is No...

Buy yourself a tool that uses compressed air to pressurize the cylinder...something like a Lisle Valve Holders 19700

remove the rocker covers, rockers and pushrods....
remove the spark plugs and screw in the tool into each spark plug hole to pressurize the cylinder...
Use an angled tool to depress the retainer on each valve spring and remove the keepers...like a Summit Racing® Valve Spring Compressors SUM-906784
remove the retainer and spring.
remove the old seal
If you see any oil /air mix leaking up the valve stem...you should remove the heads and have the guides serviced.
if no seepage
and replace with new seals and re-assemble...

Ex Sydneyite here, now living in Cherryville NC USA

[andyh1956]

Originally Posted by AussieinNC

If you are asking if the piston at TDC will hold up the valves enough to allow you to change the stem seals, the answer is No...

Buy yourself a tool that uses compressed air to pressurize the cylinder...something like a Lisle Valve Holders 19700

remove the rocker covers, rockers and pushrods....
remove the spark plugs and screw in the tool into each spark plug hole to pressurize the cylinder...
Use an angled tool to depress the retainer on each valve spring and remove the keepers...like a Summit Racing® Valve Spring Compressors SUM-906784
remove the retainer and spring.
remove the old seal
If you see any oil /air mix leaking up the valve stem...you should remove the heads and have the guides serviced.
if no seepage
and replace with new seals and re-assemble...

Ex Sydneyite here, now living in Cherryville NC USA

Be advised when using the above procedure that when the compressed air is introduced into the cyl the piston of that cyl will be forced to BDC & the engine will rotate quickly so don't get your shirt Sleeves, Chin Whiskers or Pony Tail caught in the accessories up front!

[AussieinNC]

kiwi's never wear shirts...

are always clean shaven...

and always wear a hair net when working near rotating machinery...

[ozkiwi]

[QUOTE=AussieinNC;8411541]If you are asking if the piston at TDC will hold up the valves enough to allow you to change the stem seals, the answer is No...

Buy yourself a tool that uses compressed air to pressurize the cylinder...something like a Lisle Valve Holders 19700

Thanks that is what I was asking.....I know little about my 350 and that's the way I like it as I am working on bikes pretty much non stop I prefer someone one who knows what they are doing and takes pride in there work to work on my truck...……...Unfortunately there appears to be no such person operating in Melbourne (If there is send me a name) as everyone who has laid a spanner on my truck has charged an arm and a leg and done **** work.
So now I am doing everything myself and will be doing this job myself.I don't think my ****ty little Chinese compressor is up to it but should be able to borrow one.

[hatzie]

The soft rope trick works quite well too.
My grandfather used this to do valve stem seals on his 60's Plymouth while I "helped".

Take out the battery or at least completely pull off the ground connection.
Pull all six or eight spark plugs so the engine rotates easily by hand.
Rotate the engine to TDC on your first intended victim by hand then rotate it back a bit so there's spce between the combustion chamber and the piston crown.
Stuff 1-2ft of the soft rope down into the cylinder leaving about 8-10 inches hanging out of the plug hole and then rotate the piston gently back up toward TDC til it stops and have your five year old grandson put on gramps work gloves and hold the radiator fan so it doesn't spin... see I was helping.
This holds the valves in place while you R&R the keepers, springs, and seals.
Back the piston down and pull out the rope and move it on to the next cylinder.

Gramps said it worked better than air when the valve seats were less than 100% perfect but still plenty serviceable.

[rpmerf]

I've done the rope trick on a Dodge 2.2. Worked well.

[andyh1956]

Rope works on a chainsaw to get the clutch off to install a new sprocket!

[ozkiwi]

Finally got to the valve stem seals done and no more smoke.
What was found was the seals hardened and sort of shrunk in the center.
As this was a crate motor that I bought new 5 years ago and it only has 15000 miles on it I have to assume it had sat for a long time before I bought it or they were a dud set of seals from the outset!

The shop that did it said there was no play in the valve/guides so it was worth the money just to not having my tight well performing engine look like it was stuffed every time I started it!

[rpmerf]

Good to hear you got it figured out!