..blue smoke 3rd gear only ...?

[wifehatesit]

hey all... heres one i need some help with..
i have a relatively new built 306 w/c-4 trans.. car runs 12.30's in the quarter.
however its been smoking under hard acceleration when i hit 3rd gear. 1st and 2nd no smoke. 3rd = smoke.. i am guessing the car is under more load in 3rd gear causing the extra pressure.

i just performed a compression test and all the cylinders were around 160-170... i havent done a leakdown yet. i looked into the intake as best as i could see (victor jr has long runners, cant see the front 2 or back 2).. no oil as so far as i could see. i was thinking it might be a leaky intake sucking oil out of the lifter valley... but then again it could be that, i just couldnt see 4 of the cylinders.. i just hate to pull the intake to check.

the car doesn't have a pcv system, just two breathers.. i am going to install a pcv system this week to see if it helps. the valve seals are brand new - maybe 1 month old, and they were put in right because i did them myself. spark plugs are clean... and performance is pretty good as the car is still an 11.90 12.30 car depending on tune. oil pressure is 60-70 pounds at idle.. sounds like a lot to me. i am running 5-30 synthetic.. think the oil might be too thin?

thanks for any ideas.. i hate to put a new short block in if it dont need it..

 

[90_Red_LX]

When it smokes for a while, is there a noticeble drop in oil level on the dipstick? Keep tabs on the oil level, and check it while it is hot, but give it time to let the oil settle in the pan and do it on as close to level ground as possible.

 

[jeromy]

I had the same problem on another stang that I had. You said you have a Victor Jr. I don't know what you have for a pcv system, but breather caps in the valve covers aren't enough if you're turning high rpms. An evacuation system from Mr. Gasket would be a easy fix if that's the problem. Another way but more $$$ is to buy a electric vacuum pump from "brand x" for a 1969 z/28 and hook it up in the valve cover.

 

[wifehatesit]

Ok .. heres an update of my dilemma.. just did a leakdown test, and there was near-zero leakage in every cylinder. the pressure near ripped my arm off holding the breaker bar so the crank wouldnt turn from the pressure...

also.. this is a carb'd application with a victor jr... i did the leak down test when it was cold, but i cant imagine if i was getting 1-2 percent leakdown cold that it would drop to 15-20 percent leakage warm..

again, the weird thing is there is no smoke at idle, none at full throttle for the first couple of gears, then it almost bellows out in third.

compression test came back all cylinders within 5psi of each other, leakdowns all 1-2 percent.. maybe the oil ring? maybe the intake sucking oil? i can only look down the two middle runners on each side to see if there is any oil in the intake ports (there isnt) but that still leaves cylinders 1,4,5, and 8...

thanks.. i'm just trying to narrow things down before i rip into the engine.

 

[bt15]

When it smokes for a while, is there a noticeble drop in oil level on the dipstick? Keep tabs on the oil level, and check it while it is hot, but give it time to let the oil settle in the pan and do it on as close to level ground as possible.

So, are you losing oil or not? You may be seeing a rich condition that looks like "blue" smoke leading you to believe it's something that it's not. How about when you back off in 3rd, smoke still there? Engine braking? RPM specific in 3rd gear or across the band?

If it might be a rich issue, what carb are you running? Vacuum or mechanical secondaries? What jet size? How about your secondary squirters - standard or oversize? How about the ignition system - brand, model, etc.?

Maybe you can avoid breaking into the engine if it's something external.

 

[dastang2]

my car does that now in certain gears when i get on it. turns out the silicon blew out behind my intake, coming out of the hood though.