1990 VN Commodore: Our Shed

By: David Morley, Photography by: Dave Morley

Presented by

Morley's 1990 VN Commodore Morley's 1990 VN Commodore Morley's 1990 VN Commodore
With the dead cat-converter out, Morley's gone shopping With the dead cat-converter out, Morley's gone shopping With the dead cat-converter out, Morley's gone shopping
As well as being shinier than the original, the new cat is tinier As well as being shinier than the original, the new cat is tinier As well as being shinier than the original, the new cat is tinier
Nobody appreciates an unkempt flange Nobody appreciates an unkempt flange Nobody appreciates an unkempt flange
A result that Holden's chief engineer would happily sign off A result that Holden's chief engineer would happily sign off A result that Holden's chief engineer would happily sign off

It wasn't the feared death rattles in the VN, but fixing the problem still put Morley through his DIY paces

 

Morley's 1990 VN Commodore

I took the SS for a decent run down to Philip Island the other night. Had a steak at the pub with my brother and then headed back to the Melbourne Bloke Centre. Pulled up next to a VE SS at a set of lights and I could hear a rattling noise coming from the VE that sounded like a loose flywheel. Jeez, I thought, that’s a new car to have a rattle in it like that. Bzzzt. Guess again, dickhead; it’s my car rattling isn’t it? Yep.

By the time I pulled up at the MBC, the rattle sounded like a handful of marbles in a tin can. Oh, please, no. Sticking my head under the car, the clatter seemed to be coming from about the middle of the thing, so probably not a loose flywheel then. Grabbed a piece of wood and held it against the cat converter. Bingo: Noise stops. Ah, so it’s a loose heat shield then. Off to bed.

Next day, I stuck the VN on the sticks and looked for the loose bits. Couldn’t find them. But a good sharp rap on the cat made that familiar marble-can noise. Ah-ha, it’s internal to the cat. Which can only really mean one thing; the cat-con has fallen to bits inside. Time for surgery.

Now, I could have simply welded up a by-pass pipe or even stuck a resonator where the cat used to live, but the fine for running a ULP car without the cat is more than this car is worth. And don’t think that simply gutting the cat and replacing it will fool the EPA during an inspection. Nope, because the check can involve an infra-red temp probe to the cat and if it isn’t running the right (higher) temperature, you’re busted.

So it was down to the muffler shop to buy a replacement cat. Except, of course, it’s not that simple is it? While the headers on my car are the factory ones, I don’t think there’s a single piece of the rest of the zorst that’s original. And it’s been replaced in bits and pieces as necessary. And since it was already a replacement cat-con that isn’t available any more, the bloke at the muffler shop couldn’t just conjure one up off the shelf. Best he could offer was to source me a new cat as well as a set of flanges that so I could make my own cat of the right length. This job is getting bigger by the minute.

A couple of days later, I had all the bits in hand, including a length of pipe to make the new, shorter cat go the physical distance. So here’s how it goes: First up, you weld a bit of straight pipe to each flange. Then you tie the exhaust into place (I used a ratchet strap) so that it all lines up properly. Then, you slip the new cat between the flanges (inside the pipe extensions) and bolt the flanges into place front and rear. Then you tack the cat to each flange. Drop it all out and weld it solid. Refit it, start the car and – in my case – detect a leak in my welding. Drop it all out again and quadruple weld each seam, turning the whole thing into a big, ugly boulder of solder. But one that doesn’t leak.

So don’t look too closely at my welds, ‘cos they aint pretty. But as a job the average amateur can tackle, I reckon this one stacks up, even though I’m not saying for sure this is how a muffler shop would tackle it. But it worked this time. And since early catalytic-converter-equipped cars are now more than 25 years old, it can’t just be me that’s running into this sort of problem. And meanwhile, me and the SS are back on the road, rattle-free and looking dangerous.

 

Sign up to our free weekly newsletter for more unique car reviews and features plus see the latest unique and classic cars for sale.

Subscribe to Unique Cars magazine
- Print edition
- Digital edition