Okay when I fire my car up when it's cold, I sometimes get a little bit of smoke, it is black with a purpleish tint, although most the time I get almost no smoke.

Now for warm startups - I sometimes get A LOT of Blackish Purpleish smoke, mostly after I have been driving for a while, shut it off for 5-10 minutes then fire it up. The smoke stops after about 5-10 seconds. Once again it's only here and ther, not every time I start it warm, and if it sits for more than 15-20 minutes after running before being started again, there's minimal if any smoke.

I thought it was a leaky injector, as my old injectors looked pretty old and crusty. When I pulled the old injectors 1 or 2 of them leaked a little under pressure. I replaced them with some used, although recently reworked injectors, although it did help a little, I still see the smoke here and there.

I was kinda thinking it has something to do with my Cold Start Injector, is this a valid thought? What else could it be? and why is it only here and there, not always?

 

Unburnt fuel is usually white.

Burnt but running rich is black

Burning oil is blue.

I would seem to think that the injectors are leaking, and most likely the valve seals are leaking. The valve seals are normal for all aged chevys.

 

Sounds like your valve stem seals need to be replaced - if you haven't already. I'ts not that hard to do. You just need access to an air compressor, a small whip hose, a spring compressor, and a spark plug adapter - to adapt to the compressor and hold air in your cylinder wall to keep the valves from falling in

I've had to do this to all the 7 3rd Gens I've had!

 

Hmm, okay, valve seals... makes sense, I was just hoping that it wouldn't be that. Will this cause any harm to my engine? I am hoping to get that 305 out of there by summer and replace it with a 350, so will running it until then be a problem?

Since both of you think it's valve seals, then why doesn't it do it all the time, on every start up? I don't notice any smoke when I stick my foot to the floor, it just seems to be very occasionally on cold start up, and once in a while on warm start up.

I'm not doubting that you guys are right, just wondering why it's not all the time.

Thanks guys!

 

What is the mileage on the car? Have the seals ever been replaced?

This will give a good indication of whether the seals are the problem or not.

If you are going to pull the 305 motor out, just keep the motor as is. I wouldn't worry much about the seals. Just check you're oil level periodically until you get the 350 in.

Good luck

 

Mileage on Odometer is 174k, I don't know if they have been replaced, as I bought the car used and the previous owner didn't know if any engine work had been done. It runs strong, but I don't know if it's been rebuilt, I am kinda thinking not, since I've seen 305's going for 200k+.

I didn't think I'd worry about them if I'm throwing a 350 in there soon, I was just making sure I wasn't going to be blowing up the 305 soon.

 

VALVE SEALS!