bad ring or bad valve?

[copteaser]

Help, several weeks ago my car blew a head gasket, I replaced the head gasket and started the car. After I started the car I noticed that my car is puffing blue smoke out of the oil tube(not oil stick). There is no smoke coming out of the tail pipe. When I rev up the engine the puffing gets worse. I checked engines compression and I noticed that the #1 cylider is only 55 lbs. I checked the rest of the compression and all are between 110-100 lbs. You can actually see and feel the puffs coming out. The spark plugs are not fouled by oil.
The million dollar question is this, Is there a way in which I can be certain if is a bad compression ring or a bad valve? I want to be certain what is it, before I start wondering and start to take the engine apart. ( the engine has approx, 10,000 miles, freshly rebuil).
would appreciate any help, thanks

 

[Red Regal T]

Easier to fix of the two possible problems you suspect would be a problem with the valve. If you pull the head and it is the valve, you won't have to go any further. If it's not the valve or anything else you can find by pulling the head, you have to go to the next step and pull the motor.

 

[copteaser]

yes, I am aware of this, I know that if is not one , then it must be the other, but before I start parting and check by tearing apart, Is there a test or any known trick to check the problem.

 

[Intercooler]

Sounds like a ring to me. Out the oil dipstick tube? What makes you think valve? I would think if it were a valve it would be out the exhaust or show some signs on the plugs. The rings would go in the opposite direction I would think. Still sounds like pulling it out to check one at a time makes the most sense.

 

[Chuck Leeper]

RINGZ OR VALVES

Do a leakdown. W/ a leak test, you can easily hear if the air pressure is coming back thru the Tb, the exh header or into the pan.
However, given that you have such low compression on all other 5 cylinders, it's a moot point as to "is it a valve or a ring"??
100 to 110 is WAY low for a relatively new engine..... 150 to 160 range is what I'd be looking for.

HTH,
Sorry for the problems.. ALWAYS somethin....

 

[copteaser]

what is exactly a leak down test? and how is done?

 

[copteaser]

the engine was rebuilt with 30 over pistons, would that lower the compression in the cylinders?

 

[Chuck Leeper]

Leakdown and overbore

Copteaser, the overbore actually would raise the ratio a slight bit.
A leakdown is a tool that you hook up to an air supply of around 100psi. It has a pair of gauges, 1 of which has a press. reg to it, the other has a hose connection to the plug hole.
You remove all the plugs, remove the rockers, hook up the air to the tester and set the gauge to zero, hook the tester hose to the jumper hose you have screwed into the plug hole. When this is done, the ga. will move and once the needle stabilizes, you read the leak percentage on the ga. The readings should be in the 10-15% range at max.. I like to see less than 5% on my engines....

HTH,

If you have an air supply and no tester, you can get a air hose to plug adapter fitting that's used to hold valves up when changing valve springs and use that to put air to the cylinders.[Again, plugs out and rockers off] Then listen to where the leak is, as I outlined in the first post. The fittings are cheap.
BE AWARE!! When you put the air to a cylinder, the engine can/WILL rotate if the piston is not at the bottom of the bore!!
Don't get "it" caught in a fan belt!!

 

[copteaser]

Thank you for all the above information

 

[DarkForce]

Definitely do not pull anything apart yet. Do like Chuck says and put it under pressure because no one can make an good guess at this point.

A SWAG from what I've seen over the years, your low miles and bad compression on all cylinders, I'd say you chances would be something like at least 80% bad valve job (you did get one right?) and 20% rings.

Hey Chuck, I hope your leakdown %s aren't from using total seals.

 

[Chuck Leeper]

TOTAL SEALZ

Darkforce, the 5% I look for is on engines I put together and break in and tune after being in use. Just checked the stage 2 in ol BLACK BART. It was in the 8-9% as I am running a set of rings w/ wider end gaps than usual. I'm trying the NASCAR trick that says the gas trapped between top and second ring is a cause for the ring flutter at hi operating pressures. [In my case 30psi boost!!]
Speedpro has conducted tests that show an added .001" per inch of bore on these rings significantly lowers the trapped gas psi.
So far, at boost in the low 20's, the added gap has not caused smoking when warmed up or excessive consumption.
We'll see what happens now as I'm about to turn up the wick and see if this ol hot rod will stay together at hi 20's on the boost!! [FINALLY got the fuel system and heads and turbo RIGHT!!]

The last SBC I did, [n/a engine on alky] had 2-3% after an entire season in a ft engine dragster.. That was w/ TOTAL SEAL rings...

 

[DarkForce]

Chuck, those are good leakdown %s, let us know your engine keeps performing.

I'm running total seals on the S2 engine. I went into several very lengthy discussions about ring flutter with various tech guys and wound up with a set of rings that are supposed to prevent ring flutter (excluding the normal stop / start piston motion) through about 9000 rpm which probably equates to a little heat too. If time permits this weekend, I may try to do a leakdown test on the S2 and stocker just for grins and let you know the good and bad of it for comparison.

Just curious but do you think the NASCAR application for sustained running is comparable to the short max runs we do in-so-far-as their effect on pressures and heat on the piston rings? I'm no whiz kid, just one of the dumb curious types trying to figure things out so try and be a little patient with me. I'd be real interested in the results when you really load it up!

 

[WarpSpeed]

>>>the compression and all are between 110-100


Did you have the throttle blade propped open? If not, then those readings may be about right.


I'd vote a bad ring on #1.

 

[TurboT231]

bad vavle or ring?

Teaser, do you have T.R.W. forged pistons? I had a customer blow a head gasket and after it was fixed it had about 50lb's comp. in one cylinder, turned out to be a cracked piston between the ring lands.

 

[woobybd]

How to tell a bad ring from a bad valve.

One more option to tell if it is a bad valve or if it is the rings is to run a wet compression test (add about 1 tablespoon of oil to each cylinder and rerun the compression test.) If the compression rises it is more likely then not a bad ring if not it is probably a valve.

 

[copteaser]

Thanks guys...I will keep all options and suggestion. I will be working on my car this weekend. Figures, the track is finally open and my car "craps the bed"