exhaust size

[77orange]

I am having a new exhaust put on this week. What size and type should I get. I have a 1977 Cherokee 4dr with a 360, 2 barrell carb. I would appreciate some input.

[J4GRAND]

I have a custom dual 2.5" aluminized exhaust system with Flowmaster series 40 mufflers. Real loud! One of my best friends is manager of a muffler and brake shop so I was able to get it fairly cheap. Most here say that a dual set up is not necessary. May not be necessary, but it looks and sounds good. Definitely go with aluminized pipe though. I've had my exhaust system on over 6 years and there is no rust. Also, if you have a Quadratrac transfer case, it's a little tough running the right pipe between the case and the frame.

[stpatt]

The AMC 360 engine has generaly relied on some exhaust back pressure to build Torque. Most of the AMC nuts in the late 60's and early 70's agree and swear by a restricted exhaust flow for more power. Any feedback here?????? Thanks.

[woodybeone]

Really depends on what heads are on the motor. On my cars I have the HC heads so they benefit from a larger low back pressure exhaust. On the wags are the standard heads so a real large system won't do much unless the cat is replaced as well. I think anything over 2.5 on a standard motor is not going to help it.

[Serious Johnson]

The myth of building torque by means of restricting exhaust flow probaly stems from the very real science of sizing tubing on a relatively unrestricted race motor. That's a deep topic requiring a lot of time to describe well, and way over my pretty li'l head.

Suffice to say that once a muffler is installed on a reasonably packaged street system, tuned flow is pretty much out the window, and further restricting exhaust gas can only reduce torque.

:-

[RacerJ]

I'm trying to make the same decision right now...

I've decided to go with a single exhaust, high-flow catalytic converter (don't know if they had those in 77? hehe...) and Flowmaster 50 Series SUV muffler.

I called Flowmaster to find out what they recommend, and the tech guy said it's based entirely on the HP of the engine. For up to about 250 hp, he said to go 2.5", and for 300+ go 3", and so it's if you're falling in between 250-300 where you make the choice (I would go up to 3").

I'm thinking I'll probably stick to 2.5" all the way out, since I don't think that the intake manifold, carb, and cam will add over 120 hp?

[1BDWAGN]

I am looking around at exhaust size and muffler options. According to the Dynomax website if your engine is 350 cubic inches + they suggest a 3" single or 2.5" dual. I would run single for simplicity. Then measure your current muffler and browse through their catalog and buy the largest case muffler you can fit. The larger case makes the exhaust sound less pronounced and deeper toned. That's my plan.

http://www.dynomax.com/techsupport.stm

You can see in the link above even for smaller V8s it says to go with a 3 inch single. I had a 92 Blazer that was rated at 210 hp and it had a factory 3" single.