Bluish Smoke Diagnosis From 351W

It looks like I have some bluish smoke coming from cylinder 6 on my 351 W.

Admittedly, the block is original so it might be time for me to suck it up and put in a decent short block, but the engine makes good power and pulls strong.

When idling in my driveway, the smoke comes and goes intermittently from where the exhaust header buttons up to the exhaust port on the head.

When driving, some comes out of the tail pipes when under moderate to heavy acceleration, and after coming to a stop and needing to wait a few minutes for lights to change, some smoke will exit the exhaust upon accelerating away from the intersection (slow or fast acceleration does not matter).

After diving under the truck, it looks like one of the joints on the left bank exhaust is showing a little black discoloration.

The engine idle is good although I think it's starting to foul the plug as I got a very occasional miss this past weekend when under 1/2 to 3/4 acceleration, but that cleared up after a couple of minutes run time.

After researching online, other 351W posts recommend changing the PVC valve, but my headers/intake/carburetor/rocker covers are all Edelbrock aftermarket and AFAIK, the PVC was eliminated when they were installed (I took it to a shop to have the work done as I didn't have time to do it - that was a bad decision, I know).

Any help would be appreciated.

I hope they didn't eliminate the PVC valve.  Those are necessary and except in racing they aren't removed.

It should be in the passenger's valve cover and go to the back of the carb or a port behind the carb on the intake manifold.  And replacing it wouldn't be a bad idea.

If that doesn't change the smoke situation you may have bad valve guides or valve seals.  That allows oil to be sucked into the cylinder, and that usually happens when you have high vacuum in the cylinders.  Coasting creates really high vacuum, and when you come back on the throttle you'll usually see a bit of blue smoke if the guides or seals are bad.

Seals can be replaced with the heads on the engine, but seals usually go because the guides have worn.  So replacing just the seals doesn't usually last nearly as long as having the guides and seals replaced.  But that requires pulling the heads.

Without a PCV system in place, the crankcase pressure has nowhere to go. This usually ends with oil leaking from multiple locations on the engine.
Hopefully, it hasn't been totally eliminated in favor of just using vented caps on the valve covers.

Thanks everyone.

I'll have to take a look on the weekend when I have time and might reach out to Edelbrock to see what options are available, as the heads have less than 100 miles on them from brand new, out of the box.

Gary - with them being so new, is a valve issue likely?

No, I forgot how new they are.  So not likely there's a valve guide/seal problem.

Show us a pic of how things are plumbed on the engine, particularly the tops of the valve covers.

Ok will do - and I appreciate the help.

It'll have to wait a few days as I get home from work after dark these days!

The umbrella seals will go bad sitting in the driveway on a zero miles engine. They loose they plasticity and become hard and crumble. This is very common. They can be replaced and I wouldn't put umbrella types back in. Problem is this . .once they crumble, little pieces find their way to the oil pan and clog the oil pickup screen. So pull the valve covers and look at the seals. Push on them with a thin blade screwdriver. If you see no pieces and they are flexible, your oil pan is OK. If they are hard and you see some pieces laying in the head, you better drop the pan.

Hi Pete,

Thanks for the info as always. The truck does get started and brought up to temperature once a week, and I do drive it usually on Saturday's and Sundays' when running errands or picking up lumber.

Would that make a difference?

The heads are Edelbrock RPM type - would they have these "umbrella" seals? I can't find any specific reference online.

Man, this truck...

Gary - no PCV valve - only the vented cap on either rocker cover. So, I imagine I need a valve cover cap with the angled elbow (do I need just the one on the passenger side?), clamp a hose to that, run the PCV valve inline(?) and then run the hose from that into the PCV valve port on the carb... which is currently being used to run a vacuum line to the trans for shifting.

It's interesting - when I read the manual for the carburetor, I noticed the "mechanic" had connected the PCV port to the trans vacuum line, and so I changed it to the port on the back of the carburetor, as that was what it was supposed to be for... I then blocked the PCV port on the carb and the truck started smoking and running really bad.

Changed it all back, and the idle evened out, no more smoke etc...

No, makes no difference. Point I was making is they will go bad no matter what you do, drive it a lot of not so much. Coincidentally, I am doing something similar at this time. I bought a '64 with a 292 Y-Block. Great truck, but it had some blue/oil smoke as well. I removed the valve cover, found pieces and then pulled the heads and the pan. Found lots of pieces in the pan. This is just so common. I ended up doing a "tractor" rebuild . . hone, new rings, new rod bearings, timing chain, etc. I found some rebuilt heads for next to nothing, so didn't even mess with mine. But I didn't use the valve seals on the rebuilt heads. Instead I replaced them with seals that grip the guide . .so they don't stay up at the top of the stem, like umbrella seals do. I always use this type of seal now.

Interesting, thanks Pete.

Why the heck do they use them if they are garbage?

They'll work if the guides are tight and they are still flexible. But both things go away as age sets in. Also, on the exhaust side, not much oil could enter because gas is being pushed the other direction. Hell, Chebbie only used an o-ring on exhaust valves, true :)  It's the intake that is the most trouble.

Quarterwave wrote

Gary - no PCV valve - only the vented cap on either rocker cover. So, I imagine I need a valve cover cap with the angled elbow (do I need just the one on the passenger side?), clamp a hose to that, run the PCV valve inline(?) and then run the hose from that into the PCV valve port on the carb... which is currently being used to run a vacuum line to the trans for shifting.

It's interesting - when I read the manual for the carburetor, I noticed the "mechanic" had connected the PCV port to the trans vacuum line, and so I changed it to the port on the back of the carburetor, as that was what it was supposed to be for... I then blocked the PCV port on the carb and the truck started smoking and running really bad.

Changed it all back, and the idle evened out, no more smoke etc...

I doubt you can find a PCV valve that is set up to go to a hose.  Don't think I've seen one, but maybe.  Or you may get a PCV valve to go into a hose - I've not tried.  But the best would be if your valve cover has a grommet in it where the breather valve is to put a PCV valve in the grommet.  Then a hose to the back of the carb.

And just having the breather on the other valve cover is fine.  The vacuum from the carb will pull fresh air into the on the side with the breather cap and that air will go down through the sump and out the PCV valve taking oil fumes with it.

Further to what Gary said, most PCV valves are designed to operate in a verticle-ish position. The check ball inside cannot do it's job properly with the valve on it's side.
Also, the valve cover needs some baffling underneath the side where the PCV valve goes, in order to help prevent excess oil getting sucked into it.

Hmmm ok - I'll need to call Edelbrock to see what they recommend, as I can't be the only guy to have this issue.

This is what I've found so far - at Amazon of all places:

Valve cover breather:

https://www.amazon.com/gp/product/B000CN52TY/ref=ox_sc_act_title_1?smid=ATVPDKIKX0DER&psc=1

PCV Valve:

https://www.amazon.com/Edelbrock-3593-PCV-Valve-Fitting/dp/B003EP2SGM/ref=sr_1_6?crid=M3H593DCLQ30&keywords=edelbrock+valve+cover+breather+pcv+valve&qid=1568993782&s=automotive&sprefix=edelbrock+valve%2Cautomotive%2C162&sr=1-6

Ok, thanks Pete. I'm going to call Edelbrock and ask them WTF is this an issue for $1,000-a-piece heads!

Well, so much for Edelbrock. They were unable to provide a solution.