My Son Has finally caught the car bug. He has purchased a 1970 catalina. (I love the front grille style. ) I won't bust him for buying pontiac....He got it at an estate sale for 1,300.00. It's a 20 footer with typical east coast rust. Rust is only behind front wheel wells and nothing that can't be remedied. Engine sounds great and has less then 100K.
He wants to put dual exhaust for more power. So question is " how much of an increase will he see and is it worth the expense'. I think it is a 330 2 barrel.

 

Congrats to your son, they are a good looking car. The only engines available for the Pontiac Catalina in 70 were the 350, 400, and 455. There really is no set number by going to duals because it depends on the mufflers, let's just say about 10ish. It's not an expensive upgrade, and it will sound better.

 

yes I was surprised. His first car was a 71 plymouth satelite. He must have liked it more then he let on. Having a tank of a car in HS during the late 90's wasn't a babe magnet. But he fell in love with style of the pontiac. I love the style I think he is looking for a slightly louder sound with just a kick more power. Now he can't wait for spring. I put duals on my 64 88 394. I truly feel the quicker take off.

 

In 1972, 20 net horsepower was the advertised gain on Olds 350s from adding dual exhaust. H to J (2bbl) and K to M (4 bbl) both showed that increase. That's probably a good guideline.
Terry

 

with the torgue being as high as they are with the dynamic 88 and the Catalina, 10-20 added HP will make a big differance.

 

I think it's a 350...

As for the HP increase, as always, it depends. How restrictive is the single exhaust vs. the duals? Is the carb set up to take advantage of the additional airflow?

The reality is that you MIGHT get 10-20 HP with the stock dual exhaust pipes, more with a larger, lower restriction system. Again, jetting would need to be optimized for the additional flow.

Of course, the added noise of Flowmasters (for example) will easily add 50 HP as measured by the "butt dyno".

 

I agree with everybody in adding duals with HP going up in the 10-20 range. I'm willing to put my money on 12-15.

Add headers as well, that will give a nice increase in power. Last car I put headers on was my Alero and they claimed 20HP at the wheels. With before and after runs at the track, I came up with 18