1988 vs 1989

[Guest dapy]

Based on a for sale inquiry I find that 1988 Avantis were built on Monte Carlo SS frames and 1989's were on Caprice Classic frames. The Monte Carlo SS engines and transmissions are considered higher performance

than the stock Caprice 305's. Should one expect a difference?

[IndyJimW]

I have a 87 Avanti based on the Monte Carlo SS chassis, I wouldn't say its high performance.

[Guest dapy]

Sure doesn't look like my 1989 305.

[Gunslinger]

I would think the Monte Carlo framed car would by somewhat lighter than a Caprice framed Avanti, so if everything else was equal I would expect the '87 to at least feel peppier in performance. What we don't know is whether the rear axle ratios are different, the torque converters and transmissions are identical models, horsepower and torque ratings are the same and other little differences that might be present to make a heavier car move out more quickly to overcome the added weight over a lighter car.

Those differences plus whether one car's engine might be more tired or simply in greater need of maintenance can make one perform better than the other. Differences in exhaust systems can change the performance...and if one car has a partially plugged catalytic converter performance will suffer.

On-paper differences don't really mean much after so many years.

[Guest dapy]

Would removing the cat converter make a noticeable performance difference?

[Gunslinger]

Early generation cats were pretty restrictive. Many, if not most states, require the car have a cat if it originally came with one. If the car is registered as a classic, street rod, historic or similar, they're not required to pass emissions testing in many states. That depends if you're located in such a state.

Some people take the converter housing and empty it, retaining the correct appearance. There's also adding a modern, low restriction cat that are available through speed shops, Summit Racing, Jegs and other vendors. They're not that expensive and are an excellent alternative.

Whether or not it makes a performance difference can vary from car to car. I used to have a '78 Corvette with a cat and single exhaust split into two tailpipes. I replaced it with a true dual exhaust without a converter and it really woke the car up. That's just anecdotal evidence...it might not translate to other cars.