Blue exhaust smoke

[mwredit]

I just started driving my '77 HPE after cleaning and resealing my gas tank.  My HPE now has an exhaust smoke problem now. When I start it cold and run it to warm it up, no smoke.  However, after I drive it on the road for a few minutes, I notice blue smoke from the exhaust when I accelerate hard and decelerate from a high speed.  The longer I drive it, the worse it gets.  When I start off hard from a stoplight, it will leave a good puff of smoke.  Also, when I'm on the freeway and then decelerate, it's like a smokescreen.  I'm thinking valve guides/seals. Could the oil control rings just be loaded with carbon?  I havent performed a compression test yet, but the engine runs good, nice and smooth, despite the crappy California gas we have. When I arrived home and just idling in the driveway, there was a stream of blue smoke coming from the exhaust.  The engine is original and has 105k miles.  Could this mean rebuild time?  Thoughts?  Thanks.

[rossocorsa]

At that kind of mileage I'd say a precautionary partial rebuild would not be a bad idea. You will probably find that the bores are still good but I think the main and big end bearings will be partially worn through and all the oil seals will be past their best. I imagine it would continue to run ok for many more miles but these engines are getting rarer so better to get ahead and avoid any problems. Just my opinion others may well differ, it does depend on how many miles you do really otherwise I think I might just try changing the valve stem oil seals

[HFStuart]

Smoke on deceleration is more likely to be valve guides or stem seals, smoke on acceleration is more likely to be rings. That's only a guide and not hard & fast rules.

I'd check that there isn't too much oil in it (can produce the same symptoms) and then do a leakdown test. I suspect though that you'll need to pull the motor for a light rebuild & decoke. Rings and valve stem oil seals can be done in situ but it's far simpler to pull everything out. Something I'm just about to go and do to my spider!

[mwredit]

Thanks folks, I figured a rebuild may be in order too.  Besides, this is a back burner project anyway and dont want to drive it much if it's chooching smoke.  As I live in Southern California, I dont want to get in trouble over the smoke.  I checked the oil and it's down 1/8" from full, where it was a week ago, and I've put about 30 miles on it since then. So, the oil burning looks severe enough to warrant some engine work.  I just wonder what the catalytic converter thinks of all of this?  It cant be good for it.

[mwredit]

Last year, when I replaced the cam, aux shaft and crank seals, along with cambox gaskets, I attempted to replace the valve stem seals with the head still attached, but was unable to get the spring compressed enough to get the collets off with my on-head compressor tool. 

[rossocorsa]

Last year, when I replaced the cam, aux shaft and crank seals, along with cambox gaskets, I attempted to replace the valve stem seals with the head still attached, but was unable to get the spring compressed enough to get the collets off with my on-head compressor tool. 

They are quite strong, I found them easiest to compress with the official tool which is quite a simple design but I had the head off. Not sure how easy it would be on the car

[mwredit]

rossocorsa, I used an on-head valve spring compressor, the typical kind that you find in the basic auto part stores.  I'd love to get my hands on the official Fiat/Lancia tool, though.  I attempted it, but found that there wasnt much spring that the hooks could grab on to due to the inset of the spring bases on the head.  I could only grab onto 2 or 3 coils, which wasnt enough.  I was disappointed because I had the cam boxes off and was there anyway.  I've done it on a couple of motors, a 3800 GM series 2 V6 and a 2.8 Ford Cologne V6 without much trouble. I used 1/4" rope to hold the valves up at TDC and works great. So, as far as the Lampredi Twin-Cam is concerned, it isnt possible with the head on the car.

[rossocorsa]

I'll try to do a picture of the official tool it wouldn't be too difficult to fabricate one as it's very simple but efficient in use.

[rossocorsa]

https://photos.app.goo.gl/YtPFSfkMXYVawj7H2

https://photos.app.goo.gl/HhWByCsTQkYf9QA43

You use a bolt on a spare thread which the hook part engages with, the other part is then used to push the springs down. I used a magnet pickup device to catch the collets (they can fly anywhere if you are not careful!) If you have a compressor and a leak down tester you might be able to use compressed air to keep the valve from dropping although I haven't tried that technique myself.

[mwredit]

If only I could get my hand on one of those babies.  That would work.  Thanks for the info.  Instead of compressed air, I use thin rope and bring the piston up to almost TDC until the rope compresses.  Compressed air scares the hell out of me in fear that a valve might drop in.

[mwredit]

I ran a compression test today anyway.  Here's what I found out-

Cyl #1   159     179 (wet)
Cyl #2   158     180 (wet)
Cyl #3   158     180 (wet)
Cyl #4   168     178 (wet)

The compression jumped about 20 lbs in most cylinders when I added oil for the wet test.  However, the readings were very even across the board.  The rings look a bit tired to me.  Opinions?  Thanks.