smoking breather

[SteveL]

On my 81 the breather on the right valve cover has smoke coming out of it. The PCV valve seems to be working OK and there is no smoke coming out the exhaust . Can anyone tell me what would cause that? I'm thinking it is bad rings but wouldn't it be blowing smoke out the exhaust?
Thanks
Steve

 

[Mako]

On my 81 the breather on the right valve cover has smoke coming out of it. The PCV valve seems to be working OK and there is no smoke coming out the exhaust . Can anyone tell me what would cause that? I'm thinking it is bad rings but wouldn't it be blowing smoke out the exhaust?
Thanks
Steve

It may be blow by. A leakdown test would confirm or deny that theory pretty quickly. ONe other quickie test you can do:

Warm the car up.

Pull the breather out

With the car at idle, look for a train like puff-puff-puff of smoke coming out of the hole.

If you see or can feel a significant puff of smoke coming from the hole, there is a wounded piston or some really tired out rings in the engine. This is common problem on engines with a power adder (super/turbo or NOS) and stock cast pistons.

Good luck!
Mako

 

[SteveL]

I do get the puff of smoke like you said. Would a compression test work? Not sure how to do a leak down test.If it is piston ring coud it be that it might be stuck? this motor had been sitting still for a year.
Thanks for the reply
steve

 

[Mako]

I do get the puff of smoke like you said. Would a compression test work? Not sure how to do a leak down test.If it is piston ring coud it be that it might be stuck? this motor had been sitting still for a year.
Thanks for the reply
steve

You can do a compression test, but the rings have to be pretty shot to fail. Compression tests are more useful to find blown head gaskets and other big problems, but...

Do a compression check on all 8 holes anyways (remember to pull 8 plugs first!).

Any cylinder that is way low from the average is suspect. I like to see north of 150 pounds on a stock engine, and say 180+ on a performance engine. My Vette's 383 squeezes right around 195 or so for an example.

The problem with those numbers is that there are so many variables that effect cylinder pressure - cam, valves, rings and static compression ratio, that engines in perfectly good shape may have surprisingly low compression check numbers, which is why the leakdown test is such a good idea.

Finding a friend with a leakdown gauge setup is the best way to diagnose weak, but not totally shot, rings and leaky valves. A good engine will have under 5% leakdown, anything much over 10% and it's pretty much ring job and bore honing time with a valve job tossed in just because it's the right thing to do.

Good luck,
Mako

 

[SteveL]

Thanks for the reply mako. Could bad valve stem seals be the problem? Two guys at work told me that valve seals would cause it. I just can't see how that would be the problem but they insisted that it was the cause. I can only hope thats what it is. That's a easy fix.
steve

 

[MaineShark]

Well, the intake valve stays open even after the piston is coming back up, so it's possible that some local pressure is pushing past the valve seals, but I think that Mako's idea is probably more likely. In any case, a leakdown test (essentially pressurizing the chamber, and then seeing how well it holds pressure - how much "leaks down" past the rings) will help to diagnose the cause.

A compression test would be a decent place to start. If one cylinder is dramatically lower than the others, you'd know where to look for a problem. Probably easier to just find a friend of mechanic with a leakdown tester, though, since I believe that you can do a compression test at the same time.

Joe

 

[Mako]

Thanks for the reply mako. Could bad valve stem seals be the problem? Two guys at work told me that valve seals would cause it. I just can't see how that would be the problem but they insisted that it was the cause. I can only hope thats what it is. That's a easy fix.
steve

Valve stem seals are oil control devices, not keep the compression in the chamber devices.

Remember, you have blow by getting down into the crank case and pressurizing it. It's rings, pistons and bores that should be looked at, not oil seals.

If the car was burning oil, fouling plugs and/or putting out a puff of white smoke on startup, then ya, the valve stem seals should be replaced.

CYa!
Mako

 

[SteveL]

Thanks mako I didn't think it would be valve seals. I did a compression test yesterday 7 cylinders are 175-180lbs,#3 cylinder is 120 lbs. guess I found the problem. those new crate motors sure are looking good now.

 

[Mako]

Thanks mako I didn't think it would be valve seals. I did a compression test yesterday 7 cylinders are 175-180lbs,#3 cylinder is 120 lbs. guess I found the problem. those new crate motors sure are looking good now.

You're welcome. Sorry to hear the engine has a dead hole :-/ Is there any oil in the coolant? You may very well have multiple problems. A blown gasket or wounded valve can account for the poor compression in #3.

Lot's and lots of crate engines out there. A ZZ4 from GM is a damn fine choice.

What cylinder heads are on the engine now? If they are '186 heads, a modest bit of pocket porting and unshrouding the valves will give you very nice power gains while keeping the stock appearance (if that's important to you). Plug in a warmer cam and zoooooom

CYa!
Mako

 

[SteveL]

Thanks again mako. I have no coolant in the oil and there is no smoke out the exaust.Would a blown gasket or bad valves give me the same symtoms? Stock apearance is not important. I just want it to run good. I would also like to nurse this engine threw the summer. It still runs fine.

 

[Mako]

Thanks again mako. I have no coolant in the oil and there is no smoke out the exaust.Would a blown gasket or bad valves give me the same symtoms? Stock apearance is not important. I just want it to run good. I would also like to nurse this engine threw the summer. It still runs fine.

A blown head gasket can do a couple of things:

1 - short circuit two cylinders together

2 - short circuit the water jacket into the cylinder

3 - All the Above

As to nursing the machine through the summer: If you will be re-using the block, then don't do it. Pull the engine and repair it before it gets much more expensive.

If you're intending to go with a crate motor, then run it until it dies.

CYa!
Mako