Question for the engine guru's, Smoking

[red71cheyenne]

I rebuilt the engine in the Blazer and ever since its been running, its smoked. It acts like the valve seals are bad and I'm not sure they aren't. I got the heads from a buddy on the ship and am not sure the seals were replaced when he rebuilt the heads. My question is: How hard is it to replace the seals while they are on the engine or should I just pull the heads and have them gone through again?

[swb85]

Valve seals are easy, just time consuming. It requires removing the valve springs, so you'll have to use compressed air or some other means to keep the valves from dropping into the cyl while you replace the seals.

[cdowns]

do you have a PVC valve on cheap valvecovers without baffels? a very common problem causing oil burning problems

[68gmsee]

You may want to make sure before going to all of the trouble.

Take a compression reading on all the cylinders.
Have someone start the engine after it sits for some time to see if there smoke when it first starts up.
As Cdowns mentioned, check for the baffle and make sure your pcv valve is working properly.

When the engine was rebuilt, was it rebored and checked for concentricity? If it wasn't, it will take a long time to break in especially if chrome rings were used.
Also, how many miles since the break in? Maybe it needs more time.

[red71cheyenne]

Thanks for the replies guys, it was only honed, the machine shop said the cylinders were in good shape, so I didn't bore. Its only got maybe 200 miles on the rebuild, more like 10 or 12 hours I'd say of running. My PCV is new and they are stock valve covers with baffles. The only questionable part is the heads as I just took my buddies word they were rebuilt. I guess it could just be it needs some more break in.

When I do the compression check, if it is the valve seals, what indications would that be?

[68gmsee]

A compression test is for testing for cylinder ring seal and valve to seat sealing.
A leak down test would be a better method for ring/valve sealing though.

It won't show if you have bad valve guides or need seals. The best indicator of that is to check the exhaust when you first start it up. Worn valve guides or seals will allow the oil to seep down through the valve stems in to the cylinders so that it puddles there until you start the engine. You will see smoke and then it should burn off.

For checking the valves for seals best thing to do is to remove the valve cover and check them. Be aware that on some early 350's you didn't have valve stem seals. The guides were the seals. If they were worn, you just had to have them gnurled or replaced.

If you do remove the springs to check you can use the compressed air method or the "rope" method. You can google for info on that but basically you insert the rope in the cylinder and rotate the engine so the piston pushes up on the valve and holds it in place.

[red71cheyenne]

Originally Posted by 68gmsee

A compression test is for testing for cylinder ring seal and valve to seat sealing.
A leak down test would be a better method for ring/valve sealing though.

It won't show if you have bad valve guides or need seals. The best indicator of that is to check the exhaust when you first start it up. Worn valve guides or seals will allow the oil to seep down through the valve stems in to the cylinders so that it puddles there until you start the engine. You will see smoke and then it should burn off.

For checking the valves for seals best thing to do is to remove the valve cover and check them. Be aware that on some early 350's you didn't have valve stem seals. The guides were the seals. If they were worn, you just had to have them gnurled or replaced.

If you do remove the springs to check you can use the compressed air method or the "rope" method. You can google for info on that but basically you insert the rope in the cylinder and rotate the engine so the piston pushes up on the valve and holds it in place.

I was going to give the air pressure method a try first, I'll just have to get a spring compressor first.

My engine isn't smoking on startup, it starts smoking after its been idling for a little while. If I stop at a stop light while driving, you can see the smoke coming out, but while driving under load, there is no smoke.

[68gmsee]

Actually a lot of people seem to like the rope trick. You don't have to worry about dropping the valve if you lose air pressure.

Some questions:

How many miles on the engine when you had it rebuilt?
Do you know what type of rings were used?
What type of oil are you using?

The reason I ask is that most reliable shops would never tell you that the bore is okay on a high mileage block -especially a vintage block from 40 years ago. On these old engines if it had anywhere above 70-80k it was in need of a complete rebuild including re-boring. If chrome rings were used they may never seat/seal properly.

[fastwillie 696969]

what would suck if the oil rings were installed upside down

[rickpilgrim]

The 85 350 in our 86 K10 plow truck was rebuilt by the engine shop and they put in chrome moly rings and pc valve seals. It was about 3500 miles before those rings seated and untill they did I had(when warmed up)light blue smoke at idle, a bit when deaccelorating and about a quart every 500 miles untill the rings set.
For valve seals we use the rope and a bar we made that has a 1" hole and a 7/16's hole that you bolt on the stud and push down, pull the keepers with a magnet and release, reverse for reassembly. The felpro valve seals(rubber umbrella) cost less than 10 bucks at Advance Auto and we have had some of those going for 4 yrs/73K mi and are still working.

[GASoline71]

What color is the smoke?

Gary

[fastwillie 696969]

Originally Posted by GASoline71

What color is the smoke?

Gary

mine is greyish -greenish color ,smells like skunk ,ohhh wrong smoke ,i still say the put the oil rings in wrong

[red71cheyenne]

Originally Posted by 68gmsee

Actually a lot of people seem to like the rope trick. You don't have to worry about dropping the valve if you lose air pressure.

Some questions:

How many miles on the engine when you had it rebuilt?
Do you know what type of rings were used?
What type of oil are you using?

The reason I ask is that most reliable shops would never tell you that the bore is okay on a high mileage block -especially a vintage block from 40 years ago. On these old engines if it had anywhere above 70-80k it was in need of a complete rebuild including re-boring. If chrome rings were used they may never seat/seal properly.

I have no idea how many miles were on the engine when I rebuilt it, it came with the Blazer when I bought it. It was in pieces in the back. The block is a 1977 4 bolt main and I have no idea if my rings were chrome or not. I just bought a stock rebuild kit for it and went from there. I use Penzoil 5W30 on everything, always have.

[red71cheyenne]

Originally Posted by fastwillie 696969

what would suck if the oil rings were installed upside down

I'm hoping I got them in right, but couldn't tell you for sure.

[red71cheyenne]

Originally Posted by GASoline71

What color is the smoke?

Gary

Smoke is bluish, black and mostly at idle. It doesn't show itself while driving, only at idle.

[red71cheyenne]

Originally Posted by fastwillie 696969

mine is greyish -greenish color ,smells like skunk ,ohhh wrong smoke ,i still say the put the oil rings in wrong

Puff puff pass!

[red71cheyenne]

Originally Posted by rickpilgrim

The 85 350 in our 86 K10 plow truck was rebuilt by the engine shop and they put in chrome moly rings and pc valve seals. It was about 3500 miles before those rings seated and untill they did I had(when warmed up)light blue smoke at idle, a bit when deaccelorating and about a quart every 500 miles untill the rings set.
For valve seals we use the rope and a bar we made that has a 1" hole and a 7/16's hole that you bolt on the stud and push down, pull the keepers with a magnet and release, reverse for reassembly. The felpro valve seals(rubber umbrella) cost less than 10 bucks at Advance Auto and we have had some of those going for 4 yrs/73K mi and are still working.

Yep, I already have a set of umbrella seals waiting to go in if thats what it comes to, just have to jump off the stump and do it. I don't suppose you could take a pic of your bar for me, I can't picture it in my head.