250 oil usage

[sider68]

I have a GMC pick up with about 60.000 miles on it with a 250 inline six.The problem is oil in the air breather.I replaced the PVC valve twice.I was told by one of the board members it could be blow by in the piston.I took all the spark plugs out and replaced them.They were all burning properly.I had expected to find one oily or sooty if blow by was the problem.
What next should I look for.

[crackajacka]

were any of the spark plugs bent/damaged in any way? if so you should check the compression in the cylinder. can you remove the oil fill cap and smoke blow out like a train? if so one of your pistons might have chipped and is allowing compression into the crankcase which is enough pressure to shoot oil up to the breather. if thats the case its time for a rebuild.

[bigd65]

see if you have a baffle in the inside of the valve cover. could be just sucking the oil instead of just the smoke and pressures.

[sider68]

I took it in to a mechanic and he said it is just old age and I,d have to live with it.I thought the inline 6 lasted forever.I guess my options would be having engine rebuilt or finding another one.6 cylinders are usually cheap but will I still have the same problem all over again,
Would valve seals cause this problem and aren,t they not to expensive to replace.The truck itself is rust free and worth keeping

[crackajacka]

dad told me something bout haveing the heads worked after like 45,000 or something like that

[76HighSierra]

Originally posted by sider68
I took it in to a mechanic and he said it is just old age and I,d have to live with it.I thought the inline 6 lasted forever.I guess my options would be having engine rebuilt or finding another one.6 cylinders are usually cheap but will I still have the same problem all over again,
Would valve seals cause this problem and aren,t they not to expensive to replace.The truck itself is rust free and worth keeping

If you're having oil find it's way into your air cleaner, valve seals are going to do nothing to remedy that problem. The problem is that you have either too much crank case pressure, or the crank case ventilation system is not doing an adequate job of getting rid of "normal" pressure. Firstly make sure your PCV valve is functioning properly and that you have engine vacuum present in the hose that runs from the carb to the PCV valve (engine running, of course). I have seen some older engines, especially those that sat for extended periods of time, that "gunked up" the vacuum supply line to the PCV valve, therefore rendering it inactive. If your PCV valve and supply hose checks out OK, make sure that your breather tube (runs from the rear of the rocker cover to the air cleaner, on an I-6) is clear of obstruction and has the filter pad present where the hose connects to the air cleaner. If all of these check out, have a leak-down test performed (or at least a compression test) . A leak down test is a good way of truly finding flaws that may be present in your rings/pistons, or valves. Another question, is exactly how much oil is finding it's way into the air cleaner and how often?

[sider68]

I blew out all the lines to the carb and replaced pvc valve.I checked it again and it was down a quart after a week.The air filter needs to be replaced again.
It does puff out some black smoke only upon starting up.Help as I am at a loss.
One guy told me to add Lucas to the oil and put a piece of cloth or rag in the breather hole.

[old Rusty C10]

the puff of black smoke is raw or unburned fuel nothing to do with the pcv . id bef the baffle is missing or damaged in your valve cover pull that off and check it

[76HighSierra]

Originally posted by sider68
I blew out all the lines to the carb and replaced pvc valve.I checked it again and it was down a quart after a week.The air filter needs to be replaced again.
It does puff out some black smoke only upon starting up.Help as I am at a loss.
One guy told me to add Lucas to the oil and put a piece of cloth or rag in the breather hole.

Have a leakdown test performed. You "more than likely" have bad piston rings. At very least, do a compression test. If that shows to be somewhat acceptable, THEN go for the leakdown test.

[crackajacka]

Piston rings or piston chipped

[sider68]

Rusty..what baffle might I be looking for?

[crackajacka]

when u pull your valve cover off where the breather hole is theres a little rectangle box aka a baffel. if u can see threw it to the hole is probally your problem lol you'll need to buy a new valve cover

[swervin ervin]

I agree with the guys. Pull the valve cover to make sure the baffle is not messed up or off. I doubt this is it, but worth a shot. If we were voting, I'd say your rings are shot.

[sider68]

What should I do if rings are shot?Get a shop to rebuild,look for another 6 cylinder motor.Upgrade to an 8,but can tranny handle it.I don,t have alot of money to spend on this right now.

[Russell]

350 would be your best option if upgrading to a V8 -- Parts are cheap and plentiful for the 350.

If you have the tools and the time, you could probally rebuild that I-6 yourself. Just ask lots of questions here, and get a book about rebuilding those engines.

What kind of transmission do you have? Most of them should be powerful enough to handle it (SM465, TH350, TH400, all are strong enough for a 350, easily)