How much is to be gained by removing the original cat?

[azmusclecar]

Well I will spray some PB Blaster on the nuts and bolts and see if it comes off. Measure, then decide to fix the hole or just
straight pipe it. For as much as the car is driven, I don't see it as a planet saving choice to cat or no cat.

 

[Local Hero]

My 78 Delta 88 came with brand new exhaust and an aftermarket high flow cat.

That was the very first thing I removed and it was even brand new. Straight pipe in there now. I wasn't worried about performance. I just didn't want that cat in there when it decided to go bad.

 

[Max Headroom]

There are a lot of things that can cause a oem cat with 80k miles on it to rob what little power the the low compression engines of that time had. The cars didn't have enough computer to adjust timing or fuel flow. Not enough timing or a rich mixture can cause the cat to deteriorate inside, restricting exhaust flow to a much greater extent than a new unit. (Which was very restrictive to start with.) The increased back pressure can also contribute to other problems like heat buildup, carbon buildup, valve seat deterioration and a whole a la carte menu of other unpleasant crap. In my opinion, there aren't enough of these old cars left on the road to contribute significantly to air pollution, so I would dump the old cat in favor of either a straight pipe or some kind of resonator. Remember also, that your stock style muffler is also not going to be great about exhaust gas pass through. Why make it harder on the engine than it has to be. Just a thought.

 

[69hurstolds]

According to the fitment guide, a "direct fit" magnaflow 93431 is the part for a 79 H/O converter, 49 state except California. $265.21 list price from Magnaflow. Cheaper elsewhere. $205 with their current 20% off sale right now.

$157.53 (plus any tax) shipped from Amazon.

https://www.amazon.com/dp/B000RDI52U/?tag=gbody-20

OR- you can do a Walker direct fit converter. P/N 15502. With the 5% savings discount code, you can buy one from Rockauto.com for $109.00 plus tax and shipping.

You may find it cheaper somewhere else, but probably only a few bucks. It's worth a couple bucks more to get it shipped by a reputable outlet, IMO. If you have any issues...who knows how those other guys would handle it.

Personally, if it's not a mandatory emission check now, some day it may be and then everyone will be scrambling to get a converter. Depends on how long you plan on keeping the car, future plans, etc. You have to make that call. $157 isn't a bad price at all for a new converter. Plus you can breathe easy, maybe literally, knowing that your car is emission compliant and doing its part in not turning Arizona into California. Even if it doesn't need to be compliant.

If you ever run across GM parts for it...
8998692 is the actual catalytic converter p/n.
8999015 is the bead kit for your old converter.
8998484 is the "bottom repair kit" for the converter. WTF?
8998555 is the threadless plug for the bottom.

 

[69hurstolds]

The newer cat designs aren't as restrictive as the old, pellet type used to be, so you're not going to "lose" power on an underpowered Olds V8 anyway. It was designed to suck performance-wise. The only thing you have to worry about is using tons of the zddp additives and too much can kill a cat. So if you plan on using a lot of that, then get the straight pipe and cross your fingers. Just know, with or without a converter and those rear end gears, your performance change won't be noticeable one way or another.

 

[69hurstolds]

Apparently, that bottom repair kit fixes what your converter problem is right now, I assume... it was about $50 about 35 years ago. So the price is still in line, although for this kind of money, I'd buy a new converter.

https://rover.ebay.com/rover/1/711-...0001&campid=5335822911&icep_item=323889255429

 

[TURNA]

If your cat is clogged at all

You will definitely notice a different when you install a straight pipe

 

[500/600]

Straight pipe if you are allowed. Hi flow cat if you aren't.
Anyone concerned about being "green" is hypocritical for even being on this site. These cars in original 'emissions compliant' form are miniature chemical plants by todays standards. Period.

 

[azmusclecar]

If your cat is clogged at all

You will definitely notice a different when you install a straight pipe

The exhaust seems very restrictive since I blew out 2 exhaust flange donuts at the manifold. First one was say due to age....but the 2nd???

I just replaced the donut again....and feel the CAT may be partially clogged.

 

[azmusclecar]

There are a lot of things that can cause a oem cat with 80k miles on it to rob what little power the the low compression engines of that time had. The cars didn't have enough computer to adjust timing or fuel flow. Not enough timing or a rich mixture can cause the cat to deteriorate inside, restricting exhaust flow to a much greater extent than a new unit. (Which was very restrictive to start with.) The increased back pressure can also contribute to other problems like heat buildup, carbon buildup, valve seat deterioration and a whole a la carte menu of other unpleasant crap. In my opinion, there aren't enough of these old cars left on the road to contribute significantly to air pollution, so I would dump the old cat in favor of either a straight pipe or some kind of resonator. Remember also, that your stock style muffler is also not going to be great about exhaust gas pass through. Why make it harder on the engine than it has to be. Just a thought.

Very good points.......I owned a 1978 Pontiac Grand AM from new to owning many years until my divorce. Ex-won it in the crooked PA divorce lottery,
but I digress. I'm very aware of the minimal power these engines put out but to allow it to inhale and exhale should at least help prevent some of the issues you stated. Thank you.