98blckz28

I am buying a 86 iroc tomorrow with the 305 with what I believe is the lg4. I was going to buy a set of headers for it now to get it to sound somewhat like a muscle car before I can swap the engine... but to the question. I was going to basically just run open headers on it. My buddy mentioned something about the 02 sensors. will this throw something off on the engine or cause it not to run right? I am not familiar with carb engines so any advice would be greatly appreciate on this!! Thanks!

stanghunter211

You need some backpressure for the engine to run properly. Unless you have an all out drag race motor, smaller cubes and mild motors actually need the backpressure. You will probably lose some low end power by running open headers, not to mention the smell that will come through the floor, and the ridiculous noise levels it will create. In the long run, I suppose it will be bad for the heads. Most people don't run open header unless they are headed to the exhaust shop to have some work done. Since you 02 sensor is in the header, and you only have one, it will still work, but as far as an accurate reading, I doubt it. And if the the 02 isn't working, er, reading properly, you are going to run into all kinds of tuning issues. My advice, headers and nice exhaust, sans a catalytic converter will sound plenty mean. If you want it to sound like a tractor though, by all means, go ahead!

Will

Black305RS

my exaust on my iroc is cut off at the back of the cat and it sounds really good.

Marc 85Z28

stanghunter211 pretty much summed it up, however...

Needing backpressure is a myth, so don't buy into it. Any low end torque that you think you may have lost, is easily regained by adjusting the engines tune, as freeing up the exhaust system can actually alter the engines state of tune.

I would highly recommend NOT running open headers because of the noise level, and the fact that the engine most likely won't run very well. The O2 sensor's location in the collector is just too close to atmosphere, and thus will read incorrectly.

Finally, as far as header choices go, if you want long tubes Hooker Super Comps are the only way to go. If you go with shorties as most do, stay away from the Edelbrock and Flowtech junk - they're cheap and fit well, but will hurt power with a healthy engine. Hooker and SLP make very nice shorty headers, with the Hookers fitting better and costing far less.

The good news about the LG4 is that is actually quite responsive to mods as its so restricted from the factory. The bad news is that it starts around 150HP, and even though a 30+HP gain as typically seen from full exhaust seems like a big improvement, you still have a pathetic sub 200HP engine

Jim85IROC

An LG4 with open pipes will sound like your mom's buick with a hole in the muffler. Loud and cheesy sounding. You need high compression and a big cam to make open pipes sound good.