C4 Monster

Ok I have a 1989 corvette (Just bout stock) and im down to my last problem. I fixed damn near everything and the last thing on my list for this car in terms of mechanical problems is that I need to replace the cats. So here is what I wanted to ask you, since the car has 3 cats is it possible for me to replace the back (center) cat with 1 large one and then replace the two up front (off the headers) with 2 cutouts. If so, what cat should I put in the back that would compensate for the two up front and itself, also are there any sensors that would need to be replaced or moved such as o2?

My goal is to pass inspection and have a well running car that I will always have the option to open the headers wide open.

j-wireman

I assume you meant "exhaust manifold" when you said "headers", right?
I think the '89 and '90 exhausts are identical. I don't have "headers", but here's what I did:
I replaced my front Y-pipe (with "pre-cats") with a new one without "pre-cats". It came with a welded "bung" for the O2 sensor, in the same place. For the main cat, I installed one from Random Technologies. We have emissions inspection here (PA) and my numbers are better now than with my old stock setup, according to my inspection guy.

There are different shapes of cats for different applications. I believe R.T. makes cylindrical cats, too. Check 'em out.


Mike
'90 'vert

Siveck

One of the vendors sells a "precatless" Y pipe with high flow center converter and advertises it as 49 state legal. Look through the vendors for that setup. I bought one years ago for my previous '89 coupe.

Shark Racer

While I hate pre-cats as much as the next guy, I just wanted to comment:

You will not see much (if any) reduction in emissions levels by running pre-cats. They're basically "warm up cats", they warm up more quickly than the main cat which is further downstream and minimize pollution while the main cat is getting up to temperature.

Odds are, the Random Tech cat is working better than your old main cat did.

Removing pre-cats will contribute to start-up pollution, but you'll still pass tailpipe emissions tests.

Sort of like the premise of running coolant through the throttle body. Warm the engine up as quickly as possible.

Just FYI...

levan

I have my car on the lift, planning on a loc for the wideband bung. I'm hitting a wall. Before I start, I DO NOT want to change exhaust configuration to full headers right now. Too much going on.

So, I'm looking for any ideas to get an AFR reading given what I am working with. I was along the lines of a Dashlogic then fed by a WB into the 0-5v PID. Regardless, even with a gauge I still need to get into the exhaust ahead of the cat. That is the problem.

So, here's my setup. I have Magnalfow short tube headers on right now. They bolt up to the stock cats. Again, I need to leave all this in place right now...maybe an add LTHs WAY down the list past the FI install and tune.

I cannot find a place to locate the bung. There is clearance where the wideband could live, but it's the bung location itself. Here are three pics that might make it clearer: Magnaflow pipes; stock C6 Cat; a pic of my setup, albeit no way to get a good photo. The header in the foreground is the driver's side.


thanks help me

65Z01

I agree with some of the above about losing the damn pre-cats and use a RT hi-flow main cat.

85WHITEZ51

Do you not have room to put it in the passenger header?