VCCA Home Forums TECHNICAL - 1945 AND NEWER 1949-1954 Pandora's can of worms!!

Hello all,

Would a lack of valve stem seals (which are now on order) alone make for a very smoky exhaust and road draught on a full pressure (Powerglide) 235? Before performing the work listed below it always used to puff a little smoke out of the exhaust on take off if allowed to idle for a few minutes.
As ever, there is a convoluted back-story which I'll list in chronological order;

1. Compression test average of 120psi

2. I fitted new hydraulic valve lifters (old ones worn/seized)and replaced the leaking oil feed to the rocker assembly - much better rocker feed now...

3. New lifters did not work with the 20/50 oil I had been using so I took advice to add a pint of ATF.

4. This worked for the lifters (which I dialled in further by backing each off then nipping each one up just as they'd stopped knocking). The engine however smoked a lot out of the exhaust and road draught (intermittently filling the cab with oil smoke!) during a test run.

5. I replaced the oil with 10/40 and no ATF. Which the lifters seem OK with but it's as smoky as ever.

I have yet to re-test compression but the way I see it, I've either killed (cleaned?) my piston rings during the ATF lubed test run or (hopfully) the combination of a greatly improved oil feed to the rockers and the lack of valve stem seals is dumping oil into the combustion chambers.
Any ideas as to what the heck is going on?
Any feedback would be much appreciated.
Cheers,
Tim

Which weight oil was in it when the compression test was taken?
A detergent 10-30 is sufficient. The heavy oil may be contributing to the good compression reading and the rings could possibly still be bad. I am not sure you have properly adjusted the lifters, however I don't believe that would cause the smokey exhaust. I believe the lifter should be adjusted to no noise (zero clearance) and then another 3/4 or so turn to center the plunger. That's from memory so best to check your manual or perhaps others here will confirm or correct. The ATF in my opinion is a good additive and would be fine.

20/50. I did the initial static adjustment of the lifters; finding TDC in firing order and turning the adjuster until resistance is felt while twisting the pushrod, then another 1/2 turn to pre-load the lifter. New oil appeared to make it chatter here and there so small adjustments were made while running.
The use of a more appropriate oil highlighting underlying ring issues does make sense...
Thanks for that.

Install the new valve stem seals and then after running it a while do another compression test.

Yup, another comp test and valve seals is definitely the next move before any drastic tear down. If I do the compression test while I wait for the seals to arrive, would the lack of seals give me an incorrect reading?

Not likely.

Valve seals will not affect compression, but a faulty lifter adjustment may cause you issues.

From the GM Service Manual, follow steps 1 through 4 to correctly adjust your lifters. Click below.

http://chevy.oldcarmanualproject.com/shop/1949_53/06engine/6_012.HTM

Makes sense. I only asked as perhaps any oil dripping down the valve stems may have provided an optimistic reading, as if I were performing a 'wet' comp test. You see, since my repair to the leaky rocker oil feed tube I have noticed LOTS of oil seeping out of the rocker assembly at idle with the cover off so it must be puking buckets of the stuff down the unsealed valve stems when driving. Strangely there is no return pipe as one would expect for the rocker feed so I'll have to restrict it somehow as it doesn't need anywhere near as much as it's getting right now. I'll make sure the valves are adjusted correctly as per the book too, although I'm pretty sure they're closing up nicely I'll recheck before the comp test to be safe.
Cheers all,
I'll keep you posted

You didn't mention how many miles on the engine...Rings are suspect...An old trick is to "pinch" the tube to slow down the oil feed to the rocker assembly...Try new seals and see what happens...Good Luck

No Idea of mileage. The engine itself is in a '31 Coach and I believe it's been there for at least 30 years...
Seals won't arrive for a couple of weeks.
I'll do the pipe pinch, valve re-set and comp test tomorrow and report back.
Cheers for now.
T

By the way. Rock Auto have valve stem seals on "wholesale closeout" at 60cents each. They are sending a full set all the way from Wisconsin to me in Kent, UK for a sum total of $15 and change. Pretty good deal I reckon given elsewhere I was looking at $60!! Might be worth you chaps stocking up before they run out.

Let's hope those seals are still pliable and not brittle, at their closeout prices.

Another example is buying a N.O.S. rubber whatever part that is so tough, you could use that N.O.S. part to hammer nails into wood.

Be intresting to what seals they are refereing to. The late 1947 and up head gasket sets came with the little round O ring seals.This seal was used up into the '90's. There are hundreds of them lays around.
There are also many differerent aftermarket seals and umbrellas made.
Be interesting to see what they send you.
Looking at the picture on their site they appear to be the wiper type. These will work OK on a pre 1948 which had no seal but would be unnecessary on a 1948 which had the O ring between the valve cap and stem, They also work good on small bloc V-8 engines.

Ah, it'll be fine. They're sending 12 Sealed Power ST2001s and they're going to be lovely and squishy. If they're not there's a 30 day guarantee. Either way it's gotta be worth a £10 punt
What could possibly go wrong?

The last rhetorical question was sponsored by "Blindly Optimistic" - for the eternally hopeful.

Did you really want to ask the question. I am sure you don't want to get an answer.

Correct Sir!!