I have a stock 426 Hemi that has about 3500 miles since the rebuild. it runs great, has good vacuum and plenty of power. I have noticed that after I run it hard or travel on the highway for a while it smokes blue when I come to a stop. it does not do it under mild driving conditions or at idle. I thought it might be intake valve seals so I installed a set of Viton seals on the intake valves but it still does it. After doing a cyl. leak test, the numbers look good for a stock engine, leakage in the teens and twenties for the most part. The engine has a high volume oil pump and I am wondering if its pumping too much oil up into the valve cover area under aggressive driving and pooling around the exhaust valves until it has a chance to go through the drain holes at the ends of the heads and back to the crankcase. curious if anyone has run into this problem before.
it has stock steel heads. Again, it only does it under hard driving or after a long highway run. any help appreciated. thanks

Let's start with the spark plugs,....are they installed with the spark plug compression washers on them?

Yes they are still on the plugs.

Check to make sure your PCV is working correctly. If your intake below the carbs is shiny with oil, that'd be the place to start.

My only other thoughts would be to ask what style valve seals do you have? The umbrella style or the positive seal type?

Reason I ask is that I have a similar problem with my AMC V8. After a hard romp, most of the oil is pumped into the heads (AMC's are notorious for poor drainback issues). My top end is old and worn and with half-assed umbrella style valve seals and a rocker area full of oil, lots of oil gets past the seals and into the combustion chamber.

My symptoms were also similar. Good Compression, acceptable leakdown, functional PCV and dry upper intake.

great. thanks to all for your help. I will shop around for a new set of plug tubes. thanks again.

Can you recommend a good source for new tubes?

Tubes are very hard to find right now. I had a set on order at summit that I was to get in mid august, they cancelled the order due to word from the manufactor that they are seriously back ordered. Mancini isn't ever showing them right now ( these would be m.p. ones). Found some on eBay, asked who made them and received word they were made in house, so I passed on them.

Eddy/MP heads with original 70/71 valve covers.

Seems everything Hemi is screwed up right now.

Try this, use a 12" extension with a spark plug socket installed, clamp in a bench vise vertically with the socket at the top. Put a spark plug, (WITHOUT the washer) in the socket, slide the tube down over this and lightly tap around it to reshape the tube.

Thanks for your help but I believe since this engine has Keith Black hypereutectic pistons, which require a much larger ring end gap, ( about .007-.008 per inch of bore) it will have a tendency to show higher leak numbers than and engine with traditional piston/ring combination. It only puffs blue after you hammer it. under normal driving conditions it does not do it. I will change the plug tubes and see what happens. thanks again.

I've seen 1st-hand separate issues that all created a smoking issue in 426 Hemis:
1. Guide seals: remedied by switching to hi-temp silicone umbrella seals, which were blue in color.
2. Big cam/low vacuum upsetting the carb enrichment rods to the point gas would wash the walls.
3. The spark plug tubes letting oil into the chambers as already mentioned; had to lose the sealing rings & replace the gouged tubes.
Sounds like a lot of leakage past the rings on the OP's motor.

I had a leak from the crankcase into the intake due to insufficient intake gasket thickness. If everything else is OK you might pull the intake to check it out.

When doing a leakdown check, listen in the intake, exhaust and in the oil fill tube. The hiss will tell you what system is leaking as long as the plug adapter is sealed. I have engines that run a .035 gap on a 5" bore and don't have much loss.....you set the air to 80 PSI and see what it holds at, you can have as much as a 25% loss and still make full power, while some engines lose power with only a 5% loss. I work on airplanes and every year we do a leakdown check so I have lots of experience with this. Tim

If intake and head ports are slathered with oil coating, almost has to be intake/head geometry seal. Recently went thru almost the same on our six pack 512. New set of Eddy aluminum heads all is well. My issue was severe plug fouling,,a bit different from your problem,,but same idea,,,too much oil in combustion chamber.

Machine shop that set up new heads with bee hive springs, etc. I had check for me the valve guides. They said they and seals were fine.

No more plug fouling. Intake ports are dry,,,had to pull intake again as one of my recently installed Scorpion hydraulic roller lifters decided to take a dump. .25 valve gap on exhaust number 6.

Does it ever end!

Old Hemi's don't like light weight oil use at least 20W 50and as far as the smoke is concerned Oil burning and hemi's are nothing new considered normal a qt of oil every other tankful. Until it smokes all the time I would live with it

Thanks for all of your tips. Yesterday I removed the compression washers from the plugs, cleaned up the tubes and went for a very aggressive test drive, aka, eight barrels open a lot. when I returned to my garage, I did not shut if off and went to the rear of the car because this is when it usually smokes. I did not see any blue smoke at all. So at least at this point the plug washer deal may have been the culprit. I will test it a few more times to make sure but if not, then I will look further.

thanks again.