I reckoned my 305 TPI IROC was running rather slowly so I thought it could be the cat, I decided to have a look under the car just to see if it looked like a relatively new cat and discovered that it is a rusty, crusty thing that is falling apart… So given that it looks so old and that when I bought the car the previous owner had been driving it around with a broken PCV valve and burning oil like Saddam in a Kuwaiti oil field I reckon it is definitely blocked.

Anyway, I’m by no means rich, in fact I am a rather poor so I thought I’d much rather replace the cat with a straight pipe and kill two birds with one stone, one I’d get my car running like it should and two there’s no danger of the new cat getting clogged up again.

So what do I need to do? Should I buy a tailor made cat-delete pipe? Where from? BTW, I also reckon my car is running a tad rich, my dad was driving behind me and said he could see a bit of black smoke, would that most likely be the O2 sensor?

PS: Legality? I have a 1990 IROC-Z, it is totally legal to run it without a cat, right?

I really do hope that this makes the car run quicker, I have been very impressed with the smootheness and the handling of the car... But even though it is only a 305 I did expect it to be quicker.

 

Firstly, I'm not sure when the ct was compulsory on cars in the UK. I'm thinking 1991? Comfirmation someone please!

Secondly, when I got my car it already had the cat removed and simply had a length of pipe welded in it's place. This appears to be a cheap and effective way of getting rid of the thing. So I would say that a cat delete kit is not necessary.

As for your O2 sensor. How old is it? Probably too old. When I linked an O2 sensor up I discovered the O2 sensor was scrap. Made do until the exhaust was getting work and it was 10 times better with the new one.

Also, no problems with emissions with my car, and it was nevet too sluggish either. 87 305 Auto did 60 in 6.2 0-100 in 14.7 seconds and would easily do 140mph, 155mph down a big hill with a few basic mods...and a hill. My thanks to Prime Minister Blair and the local p[olice for allowing us to use a closed section of road. I now have no need for big hills

Robert

 

Also, how much did you pay for your car? I'd like a '90 just for collection sake. What sort of milage etc?

Thanks

Robert

 

I paid £4400 for it, it is really looking lovely! The interior is almost mint and the paintwork is fantastic!!! I am very pleased with it actually, it has a few issues but overall it is a great car, now my daily driver.

And mine isn't exactly sluggish, but it doesn't feel as snappy as some of the other V8 cars I have been in... BTW, there's no way my car is doing 0-60 anywhere near 6.2 seconds!!! 7.5-8 at best I reckon.

BTW, do you get any rubber when you floor it from standstill without standing on the brakes? How about when it shifts gears? Any wheel spin there?... Mine doesn't much, sometimes depending on the road from standstill, never really when shifting from first to second and rarely when downshifting when you boot it at around 20-30 mph.

 

The 4 gas test was introduced during August of 1992, so your car will be fine without a CAT. Interestingly, there is no law that states a car post 1992 should have a CAT. As long as the emissions are low enough to pass that's fine. There are a few engines out there that run clean enough to pass this 4 gas test without a catalytic converter.
get a pipe welded in. I cut both ends off the cat and welded a straight pipe inbetween them. This way you can still use the slip joint at the front and the flare at the rear. I have done this on both my camaros.

Hope this helps.

Andy.

 

cool, thanks for the advice guys, I will do that then.

 

When my car was stock it would smoke the tyres easily from a standstill. I would also spin them by kicking into 1st from 25-30mph and I could also spin them when shifting from 1st to 2nd and I have 2.73 gears. Maybe a tune up is in order? Pitty you weren't nearer to me or I'd come round and have a look at her

Also, what colour is she?


edit: just saw your other post. She's blue!

 

Thanks RMK, now I know it should be running better. I did suspect it, I didn't expect it to feel like some of the muscle cars I have been in given it is only a lowly 305, but I sure expected it to be quicker than it is at the moment.

I'll change the cat and O2 sensor first and then I'll book her in for a full service.

 

Might also want to check the plugs, cap, rotor, wires etc. When I got my 87 they were still the ones from the factory and had seen better days.

 

right, yeah they look quite new actually... I hope most of the problem is the cat and O2 sendor, but I'll have a full service done in a of months anyway (can't afford it right now)...

 

Hi guys,

I removed the cat from mine when I had the LG4. I just welded in a new centre exhaust section of 3". Made a noticeable improvement in sound and performance. It was a strong 305 and I would get tyre chirp on the 1-2nd upshift. Although relatively low on HP it was quite torquey and I could easily light up the tyre (no POSI then) from rest.

Rob, exactly what cars do you have so far in your collection? Don't you have a C5 too?

 

Felix,

Unfortunatley I don't have a C5. However, my dad has been muttering about them again in the summer, so in short I hope to steal that one IF it ever happens.

I've got a blue 95 vert Camaro in CT that I use in the summer months.

I HAD a blue 85 a few years ago but it was a beater. Fun as hell though. I pegged the 85mph speedo right round the clock so it was pointing at 15mph.

I think the next project will be a C4. That's the current thought.

What are your future plans for the IROC Felix?

 

hmmmm, i keep thinking about this cat deleate thing myself.... what do you do with the AIR pipe that goes into the cat?

BTW, car was MOT'd today, Co was 0.00% (allowed 4.5%) and Hc was 35 (allowed 1200)

so the cat can't be clogged, and is still working!

 

Hmm, the air pipes, yeh I know what you mean. Don't know about that one. When I had my 78 Caprice, US Automotive were able to supply an exact cat bridging pipe. Certainly the CAT's getting "blocked" I've heard of before & the power boost should be noticeable when removed. One thing I'm not sure about here is would removing the CAT unbalance the Engine Computer Management system ?

And hey, don't knock the 305's.

 

No! And my car is only a 305 too.

 

OK, got the cat deleated... Yes, theres a bit of a performance increase. One lil drawback though, my car burns a little bit of oil but it didn't really used to smoke before. Now there is a bit of smoke.

It's one of those cases of but

 

IF removing the cat you may as well remove the air system as well
all it involves is a heap of swearing to undo the tubes into the exhaust manifold (hmm a good time to do a header swap ) if no header swap get some threaded plugs to block the holes in the manifolds
then elete the pump and associated wiring .......easy

 

I have found that this method helps me with just about every job I have ever done on the car. It really does work!

 

Another way: just tap the inside of the cat in pieces and suck it out with a vacuum cleaner.
Leave the cat body where it is.