Pontiac Engine Smokes...after shifting gears

[74Transam]

Well I have had this car for a long time. The engine was built 16-17 years ago and had a much larger cam in it before I bought the car. Since I have bought the car I drove it like I owed it but have put lots of time and money into it along the way. I am planning on building a 400(73 block) to replace the 350(68block) I have in the car now but I am unable to afford it at this time.

I have had a problem where the engine will smoke when I open it up before and it seems to have been rectified along the way. I have done to top half of the engine. Last summer I developed a new problem and that is when I take off from the line it doesn't smoke but when I put it from first to second it bellows smoke out the back. Same from second to Drive. I have replaced the trans modulator and same results. Anyone have an idea to push me forwards??

[maxwedge]

Black smoke is unburned fuel, not oil.

[74Transam]

The black smoke I get is right when I hammer the gas and I do know that. I am an electrical guy. I get a white maybe a slightly bluish smoke and as it's automatic I am just holding the pedal at one point. I replaced the trans modulator as I was hoping it was sucking tranny fluid through it.

[SpinnerCee]

Don't guess for one -- If the engine was sucking tranny fliud through the vacuum modulator hose it would certainly be present in the hose.

Your issue is probably a carb tuning issue more than anything else, especially if you have a Holley, you may need to pay attention to the jetting and squirters, both on the primary and secondary sides, the power valve, and the secondary mechanism.

The float level may be to high as well -- jet extensions help dumping excess fuel under acceleration too.

When you shift gears with an automatic, you're just telling the tranny to do its thing (unless you have a fully manual valve body), so the RPM drop, and your throttle output may not coincide with the air avaialble so you may be dumping extra fuel as you pump (or don't pump) the pedal between gears.

[MrPbody]

When the engine drops in RPM between shifts, there's a "jump" in manifold vacuum. A slight "puff" of smoke will come then if the guides or valve stem seals are unhappy. It's drawing oil through the intake guides due to the high vacuum.

Another test would be to put the selector in 2nd, and take it up to about 4,000 RPM and back off, allowing engine braking to slow the car. There will be a BIG puff of smoke if this is the problem.

Jim