truc still smokes..

[70c10guy]

Hi all, I replaced my valve seals yesterday with positives on intake and umbrellas on exhaust. I'm still getting blue smoke after I let off the gas when I shift! What could this be? I ran a compression test and numbers were in 160 psi range which is decent. Pcv is working, and I just did my intake gaskets today because 5 of my lifters collapsed. Also has freesh oil in her as well. It's just goes on and on repairing this truck! What could this smoke be from? I feel like I've done what I can to control oil consumption.

[OL SKOOL]

Sounds like it could be valve guides.

[70c10guy]

Valves were nice and tight to their guides!

[geezer#99]

What motor?
Where and what do you have for an air breather?
What intake?

Do you have a pic of your motor?

[hamjet]

I don,t know what you have for a transmission, but if its an auto with a modulator valve you can be sucking trans. fluid if the mod. valve is bad making it smoke..

[Wrenchbender Ret]

Make sure you have bafels in the valve covers around the PVC valve. It can suck up oil if it splashes around the PCV valve. Even if the compression rings are good the oil rings can be wore out. Pull the plugs & see if there is buildup of carbon on all the plugs or just some cylinders. With lifters collapsing & all you may be due for an o-Haul or Mr. Goodwrench.

[Grumpy old man]

Sounds like now you have a tight top end and worn bottom if it's needing valve seals and has 5? Collapsed lifters your throwing band aids at a broken leg .
Posted via Mobile Device

[davepl]

Now you finally have the excuse you need to buy that leakdown tester you've always wanted. It's time. They require compressed air, though. But if you have access to even a small portable compressor, they're perfect for diagnosing this kind of situation.

[GRX]

x2 on leak down tester. Smoke when letting off the accelerator, especially going down hill, is a classic sign of oil being sucked past the rings.

[davepl]

Originally Posted by GRX

x2 on leak down tester. Smoke when letting off the accelerator, especially going down hill, is a classic sign of oil being sucked past the rings.

Or the valve guides, or the PCV, or somewhere... and that's the beauty of the leakdown test, you can find out exactly where the leak is rather than just knowing there's a leak.

Of course a little experience with it helps, but I bet you could hear the air coming past the guides if that's what it is. I don't imagine it takes a big leak at a guide to be a big problem.

If it's weak rings you'd probably have more flow but it'd be into the oil pan.

Kinda makes me wish I had a broken engine so I could use mine! Well, not really.

[67 chevelle]

Originally Posted by hamjet

I don,t know what you have for a transmission, but if its an auto with a modulator valve you can be sucking trans. fluid if the mod. valve is bad making it smoke..

very possible , its happened to me

[70c10guy]

Thanks everyone, it's a 307 with 416 heads on it. 268h cam and lifter kit a couple months ago, t5 trans so no mod valve. I'm thinking it's the oil rings because compression was fine. Will do a leakdown on it and see what results are. Also valve covers are baffled.

[GRX]

Originally Posted by davepl

Or the valve guides, or the PCV, or somewhere... and that's the beauty of the leakdown test, you can find out exactly where the leak is rather than just knowing there's a leak.

Of course a little experience with it helps, but I bet you could hear the air coming past the guides if that's what it is. I don't imagine it takes a big leak at a guide to be a big problem.

If it's weak rings you'd probably have more flow but it'd be into the oil pan.

Kinda makes me wish I had a broken engine so I could use mine! Well, not really.

PCV problem tends to be more consistent. As you know, valve guide issues are worst after sitting. Big puff at start up when oil that is sitting atop closed intake valves is burned. And volume there is nothing compared to potential at the rings. When letting off the gas, particularly going down hill, a higher vacuum situation is created fogging out those behind you.