i have recently swapped my 305 for a 350. i removed all my egr and emissions junk. i am wondering if the oxygen sensor will operate correctly without everything. is it worth spending 20 or 30 bucks on? will it help my gas mileage at all?

 

Need way more info on the car. Also what "emissions junk" was removed.

 

If the car is still computer controlled, an O2 sensor would be needed I'd think, the ECM gets info from it to richen/lean out the fuel mixture and to retard/advance timing. Swapping for a 350 would also mean you'll need a knock sensor for a 350 car if I remember correctly, so the ECM gets the right knock counts to advance/retard timing.

 

it's a 1985 firebird SE. originally can with a 305 , with a 4 barrel quadrajet. now has headers and an edelbrock air cleaner. only thing stock on the engine would be the intake manifold, and carb, still has air conditioning, but all the egr has been removed (smog pump, exhaust manifolds, stock y pipe, snorkel air cleaner, egr valve is still on the manifold, but its capped off.) what other info would you need?
i imagined it would at least help if i bought an o2 sensor, but i heard that not having the smog pump pushing fresh air through, it would give it a false reading. any comments or suggestions?

 

If you've got a carb the engine is not computer controlled so the O2 sensor would have nothing to do with the engine. Yes?????

 

 

Thats exactly the info I was looking for. That emissions stuff is ok to remove and should allow the ECM to continue to function. Because your still using the stock intake you really should install the O2 sensor for reason listed below.

Unfortunetly this is not true. Traditionally a typical carb needs no computer but in this time period GM was trying to make the transition from carbs to fuel injection. The result was a carb that had a computer controlled mixture control solenoid to give the ECM some control over the AF ratio. Also the distributor is computer controlled. So you need to retain the original sensors for these system to function correctly or swap to a non computer controlled set up.

Now a note about the O2 sensor getting leaned out by the air pump this dosnt happen. The air pump works by diverting air to be pumped into the cat, the exhaust manifolds or vented to the atmosphere. Normally its diverted to the cat to help it burn the exhaust gases but since this is after the 02 sensor it has no effect. When the cars warming up its diverted into the manifolds to help warm up the 02 sensor. This would seem like it would cause it to run lean but at this time its in open loop operation which means the 02 sensor is ignored anyways. So basically youll be fine.

 

Factory carbed cars in this era are computer controlled!

 

thank you very much for your help! they had some ridiculous stuff on these cars, all the egr and a.i.r. systems just require way too many components. i would like to keep my computer controlled quadrajet, but i don't think it would be worth keeping after i get a new intake manifold and HEI distributer. But that's a completely different thread!!

the original distributers aren't HEI's are they?

 

the quadrajet on these cars was computer controlled, unlike the vast majority of carburetors of the past. M/C solenoid, vacuum advance, and all that good stuff would not be found on my car otherwise.

 

The factory distributors are actually HEI distributors. An HEI distrbiutor is any distributor that is High Energy Ignition - was introduced by GM in the 1971, and was standard on cars after 1975. It eliminates 'points' and condensor and uses an internal control module and magnetic pickup.

But - for the aftermarket crowd, it became a habit of calling the aftermarket HEI distributors HEI, since it became very difficult to even buy the old points-type distributors, and most 'classic car' owners eventually changed over to the improved design of the HEI system.

http://en.wikipedia.org/wiki/High_energy_ignition

The REAL term that should be used to distinguish between the two would be VACUUM-ADVANCED HEI as opposed to just HEI - since the aftermarket HEI dist that most folks refer to for a non-cc car are vacuum advanced, and the factory HEI dist is advanced mechanically via the ECM.

You CANNOT swap in an aftermarket HEI vac adv dist and keep the factory carb and the ECM. The ECM controls the distributor, advancing and retarding timing based on O2 readings and knock sensor readings. Without the factory distributor, you might as well ditch the factory carb and the ECM. (note - I guess there might be a way to tune the factory carb and keep it, but without using the TPS, IAC, etc and without using the ECM - but what's the point?).

For a carbed car, you really cannot do better than the factory setup. The Quad gets great gas mileage, will function well and serve alot more hp than the factory motor, etc. You need to keep the factory carb as well as the factory dist and ECM until the point that you have an engine making greater than 400hp or so, as the factory setup really is the best (hard to believe that a factory setup could be so great, but it's true - very versatile).

All that being said, there are aftermarket HEI factory-style distributors available - but if yours ain't broke, no need to replace it. You can get aftermarket higher voltage coil. But unless there's something physically wrong with your current factory dist, replacement of it won't yield you any noticeable gain (wasting your $$ if it's not broke).

Make sense?

 

That's the epic thing about these boards. Knowledge!!!

 

thanks a lot for the help. i felt like i was on the right track, but wanted to make sure. what if the cap and rotor don't have the brass terminals? does that just mean someone before me put on a cheap cap and rotor? or is there any significant difference?

 

No significant difference. And not all brass is 'brass' colored.