i didnt think the early cars had cats at all?

 

Marc - thanks for the pic, very helpful

If I remove this will I get lots of popping when I let my foot off the throttle? I am not a fan of that since it sounds like one of those old camaros or mustangs.

 

The decel alve prevents overly rich conditions as the responsiveness of the air plate arm is less than that of the throttle. This is, when you release the accelerator really quickly the arm closes more slowly and too much gas gets pumped into the cylinders.

There's no advantage in deleting the valve if it's working right. The common problem is that the idle speed sticks high as the valve is sticking open a bit.

I actually put on a new one a while back. (K-Jat car) Got it cheap off eBay. The same part is used on 930s and was listed for that. I've got the control line disconnected now as the car is tuned up a bit with more spark advance and a richer mixture to get a few more track ponies. This made the idle go to near 2000RPM when hot.

The negative side is that when closing the throttle quickly the car will backfire in the exhaust system pretty violently. When at its "best" fire will shoot out the tailpipes. I've got to close the throttle carefully to avoid that.

While "cool" I am concerned about the long-term effects. Don't want to spread my exhaust system around the track.

 

I have never noticed any popping on decel. I don't track the car, so it may be that I'm not pushing it into that zone.

 

I used to get popping on decel in my car, but that was before I started rebuilding. Mine could be not functioning properly. I'll see if I still get popping once everything i done. I would shoot fire every once in a while too.

 

I only get popping if I accelerate at high rpms, then suddenly lift my foot all the way off of the throttle. If you have a cat you may not get anything.

If you are a smooth driver (I try to be), then you anticipate and modulate the throttle, smoothly up or down.

Unfortunately, 'honey bunny' thinks it's an on/off switch - gas or brake, even on the highway.
...

I noticed that the more hoses I took away from the throttle body, therefrom the more manifold vacuum I measured, the better the throttle response.

Next chapter: removing the venturi connector (the 'Y' on the top of the plenum)!

 

Along with popping, when I was putting 299rwhp down, I used to get pops and flames from the tailpipe.

 

reviving this thread because i think i have the same problem..i fixed up all my intake hoses and now have a oscillating idle..runs up, abruptly drops, runs up, etc etc.

Since i have an '81 5 speed, I decided to put longer hoses on the throttle and bring the decel valve out where i can get to it (don't want to have to tear that spider out again if possible). This way i can try "capped" first, and if i have any problems i can buy a new valve.

I noticed there are actually several different model numbers to these valves, apparently they have different "activation" vacuum levels for when they open up

 

You might try raising the idle 50+rpm when it's capped. That might help if you find that you are stalling with the 5-speed.

 

Ken,

Do you see any reason why a boosted car would have any additional issues with this deletion? I have mine apart now and would like to use the top port for a boost recirc valve.

Thanks

 

Mine is about to go back together all clean and pretty and I don't need this distraction

 

I picked up some blockoffs today. could some1 post pics of how the lines are run. my valve was moved by the PO and I want to do the delete but also want to make sure the lines are run correctly!

thanks in advance

 

What would be the effect on emissions testing in a full blown state like California?

 

I have a 82 that I put a 83 euro in and want to know if I can remove anything else as far as vacuum or emisions.

 

i yanked this bad boy, and have had no troubles at all.