Ok, so here's the deal. I just picked up an overall very sweet '85 Firebird S/E for $400. It's got an LG4 305 and auto tranny. I was told by the guy I bought it from that he thought it needed a headgasket because when it warmed up it started smoking a lot. I have run the car a little bit (not up to operating temp yet) and the engine runs and sounds awesome (aside from the typical puff of oil smoke on startup from valve seals)!! I was going to start working on pulling the heads off today, but I popped the radiator cap off and the radiator is almost totally full and the coolant looks great. It doesn't look contaminated with exhaust like I would expect. I went ahead and pulled all the spark plugs and checked them (pain in the butt with all that emissions garbage on there!!) and they were all damp with fuel/oil which didn't surprise me. One seemed wetter than all the others, but it still seemed to be oil/fuel, not coolant. Another of the plugs was totally dry and a bit grey-ish in color, but still no evidence of coolant that I could see. The other weird thing is that the dipstick shows that the engine is probably 1-2 quarts high on oil, but the oil doesn't appear milky, but looks almost brand new. Anyway, I'm just looking for some opinions on whether I should tear into this thing and do headgaskets and valve seals or not. I think tomorrow I'm going to start it up and let it run and warm up and see what happens, but I'd love opinions, and ideas on other things to check to verify if it's a headgasket or not. Unfortunately I don't have access to a cooling system pressure tester right now, or a compression gage. Anyway, any and all help is greatly appreciated!!

-Paul

 

Smokes when warms up = oil drainback holes from the valve covers plugged with sludge

You might have scored an OK car; try a set of VC gaskets and a coat hanger. I'd leave the head gaskets alone for the moment.

 

oh, that sounds like I might get off with an easy fix. I'll have to check into that, thanks for the idea!!! Here are some pics of the car: https://vspace.vassar.edu/paphillips/firebird The ones that are numbered are the ones the guy sent me when I inquired about the car, the others are some that I took tonight when I was working on it. Let me know what you think, and more ideas are welcome also, in case the coat hanger idea doesn't work

-Paul

P.S. just curious about something...the car has 2 sensors that look like map sensors, one is over by the esc module and the other is mounted to the top of the cowl by the heater box. The one by the heater box doesn't have a vacuum line going to it though. Is it supposed to? What is the purpose of having 2 sensors like this on the car?

 

It's the "baro sensor".... measures ambient air pressure.... obviously vacuum is the difference between the 2, so it's a more accurate way of measuring than a MAP sensor alone.

 

ok, so it shouldn't have a vacuum line going to it then, it needs to sense what the air pressure is around it, not in the manifold, correct?

 

Yup.... one pressure sensor for what's inside the manifold, one for what's outside, and the ECM can see the difference; instead of having to assume what the pressure outside it is.

 

Well, I went over today and ran the car for 20-30 minutes, it came up to temperature, hovered a bit below 220, held 35-40 psi of oil pressure and ran great with NO smoke coming from the exhaust. The only smoke that came from the car was from oil residue and dried leaves burning off the cat and intake manifold. The engine shakes a little when you bring it up off idle, but that doesn't surprise me since the carb has 160k miles on it. Anyway, I'm glad I didn't take anything apart on the engine, since everything appears to be in good working order. I'll find out how she goes down the road once I get the plates on it tomorrow. Anyway, I'm pretty excited about how it appears to be turning out, I'll keep you posted if I run into any more problems! Thanks for all the help!!!!

-Paul

 

One more question. I went over yesterday and changed the oil in the car before I took it out of the garage to drive it for the first time. There were signs of coolant in the oil, but it didn't seem like there was a large quantity of it, although it was hard to tell. In any case I decided to go ahead and change the oil and drive it, and I still haven't seen any smoke (other than some oil smoke) coming from the car. Is there any way that coolant could get into the oil without being burned in the combustion chamber (aside from a cracked water jacket in the block or something like that)? Could a headgasket leak directly into the crankcase bypassing the combustion chamber? I just wanted to get some opinions on that. So far the car seems to drive great aside from not having much bottom end power, anyway thanks for any and all additional help!!

-Paul