help with cat please

[81SPIDERMATT]

81 spider .... 1 3/4 inch pipe ..... old cat was removed and straight pipe from front to new muffler in the back .... I now live in emissions territory and need to put a cat back in ..... options are making my head spin .... would prefer a high flow option .... I have no idea how big the old one was .... I see them from 13 inches long to way too big .... round or squashed? .... hoping the brain trust here can push me in the right direction .... thanks ... Matt

[klweimer]

I had the same issue. I purchased a Magna Flow cat on ebay for $160 bucks. 4 bolt flange, dropped right in. It was listed at $184.29 or best offer. They took my offer. Looks like they're still available, free shipping. I just passed emissions, no sweat. 82' FI.
http://www.ebay.com/itm/MagnaFlow-Direc ... 3ac70785de
Kirk

[divace73]

can't help but think MEOW when I read cat, keep us posted...meow

[81SPIDERMATT]

75 BUCKS TO THE DOOR .... cute little cat .... meow ..... car is at the muffler shop as we speak ..... then emissions .... fingers crossed ... smelling a little rich lately ... we will see how she does ... Matt

[So Cal Mark]

putting an overly rich mixture into a cat will cause it's untimely demise.

[klweimer]

81Spidermatt,
I don't recall if your car is fuel injected, I think it is. If so, you can monitor the output of your O2 sensor by teeing in a lead to a DVM and running the lead into the cabin, where you can watch the sensor output at all speed regimes. Yes, it moves around a lot, but you can quickly get a sense for where you are. I did this not long ago, along with a new cat and passed Colorado emissions, no sweat.
Kirk

[81SPIDERMATT]

it is fuel injected ..... is a dvm a digital volt meter? .. if so what would the readings mean? .. I say I think its rich because of gassy smell .... but research says that could be a few different things ... car has been stored for over a year and just getting back on road .... enjoying having it back so much that a little smell has not bothered me much...yet .... but for sure need to look into why .... it could also just be oil smell on exhaust .... I know that one or more of my manifold bolts is weeping oil ... need to investigate that further also .... Matt

[lglade]

Your gassy smell may be your old fuel hoses cracking and oozing. If they haven't already been replaced, then you should make plans to do so. I started with the high pressure hoses in the engine compartment and then replaced the low pressure hoses back to the tank, including the vapor collection system. That resolved my gassy smell problems

Midwest Bayless has a nice kit of the right diameter & length hoses for the high-pressure side. It's a little expensive at $58, but the diameter is just right to reuse the little 'bell' collars, and the lengths are just right to make re-installation of the injectors easy. If you do it, plan to replace the injector seals as well.

https://www.midwest-bayless.com/p-8163- ... 80-on.aspx

The whole project can be done in a weekend pretty easily.

[klweimer]

If you read through this article, it talks about how to hook up the digital volt meter.
http://www.hiperformancestore.com/ljetronic.htm
The short answer is that a reading of .45 volts off the O2 sensor is about where the optimal fuel/air ratio is. Of course it never actually sits there and can fluctuate quite a bit. The reading will get more stable if holding the car at a constant cruise speed. At idle, the sensor cools off and loses it's accuracy, so you have to have the engine running above idle to get reliable readings.
Kirk

[81SPIDERMATT]

great article ..thanks for that .... need to read it like three times and then have computer next to car and go thru everything .... no performance change that I can tell by putting on that cat ... high flow description was right .. little soft edge around exhaust note but not much difference

passed emissions "with flying colors" is what she said .... don't know what all the numbers mean but happy I passed .... and then an unreal 10 minutes at the dmv and my 5 year collector plate is being mailed ... yeah ... big yeah ....

front brakes are squeaky and now I remember why I have new pads and rotors in a box .... will be going thru the car with a fine tooth comb over the next few months .... glad to be back on the road .... Matt

p.s. is Brad still around ? .. seem to remember a great tune up procedure from his knowledge base also