What size/kind of pipe do I need to use. I am gonna cut my cat. converter off, and weld straight pipe all the way back and finish w/ dual tips. Thanks

Colby

 

No Cats and straights is gonna be loud as ^&^#$%. I had 2 1/2 inch straights with no muff or cat on my truck...You could hear me 3 miles away and it sounded like I was right in front of you....4 tickets in 3 days!!! Atleast get a bullet muffler... I'd say 2 1/2 inch for the pipe....

 

Straight pipe = straight ghetto
unless you are running an over the top motor you will lose all your back pressure and that means on a street motor no torque, and if your motor doesnt have a lot of top end kiss bye bye to any fun at all.

 

 

well then five7 kid, i am listening and would love to hear your explaination about why running no mufflers is great for street motors. dont forget to mention that running straight pipe for long periods of time can warp exhaust valves, oh and the whole lack of back pressure on a street motor and how that affects torque. looking forward to it.

 

yea...ive had my exhaust come off for some unknown reason. it was hanging from the middle of the exhaust system and i tell you...i felt a huge power loss both tq/hp. i needed that back pressure. unless your running some motor with good hp, your goin to have a loss.

 

I have disconnected the exhaust pipe after the catalytic and turned the car on just out of curiousity before to hear how it sounds. It felt as if it had MUCH more bottom end torque with the muffler disconnected, and it would rev considerably more freely. Thats just my experience though.

By the way, unknown host....how does running a straight pipe for long periods of time warp exhaust valves? I'm curious.

 

the catalytic converter provides plenty (hehe too much imo) of backpressure, so you probably noticed significant gains because even tho you took the muffler off the cat still provides quite a bit of back pressure. actually if i had to go smog legal, i would probably only run a cat and some kind of race muffler to keep from backfiring when you let off the gas.

as for the exhaust valve thing, i hear it everytime this comes up. i have heard that since there are no mufflers on the car the exhaust valves are exposed to greater temperature changes, not sure if this is the actual reason but there is a scientific reason i have seen.

 

Backpressure (aka restriction) is never good...
I have 3" duals on my 305 and it runs fine. I get plenty of low end tq.

 

But do you run mufflers?

I am not saying corking your exhaust and having tons of backpressure is good, I am saying slight backpressure is a good thing to have as it helps scavenge the exhaust.

A real world example:
My friend has a little beater pickup, we hacked the exhaust off before the catalytic converter and put a glasspack there, the exhaust ended basically underneath the passenger's feet hehe. no backpressure. he got sick of the drone and decided to get a dynomax turbo muffler and run pipe back to the axle. suddenly, his truck is torquey again and fun to drive. i think that if you put dual 2.5" or dual 2 1/4" on your 305 you would feel a lot more torque. 3" is too big for 90% of 350's.

 

Yes I do have mufflers, though not much (you can see tight through them... ) I know 3" is way overkill for a 305, but soon I will be dropping in a 383 or 400, so that's why I decided on 3".

 

When I had my lg4 I had no muffler and removed the cat and definately got a seat of the pants difference for the better. The reason you got the good ol was because backpressure is always bad. It costs you both power and torque. The thing however is your exhaust has to scavenge. That means that you have to have a well designed exhaust. The thing about warping the valves. I dont think you will really have much of a problem with that unless you are running open headers, because it takes long enough to get that cool air to them through the pipes that they should be fine. Search backpressure and scavenging and you will find some interesting information and debates.

Ben

 

My car has a Blown 454 bored to 468 and I was just wondering if would sound alright w/ straights, right now Im running open Hooker Super COmp headers

 

I bet it would still be loud but it might move some of the loud toward the back instead of coming out right in front of the driver(you). I think I would like it, but a lot of people on here dont seem to like the sound of straight pipes although that may just be because their motors aren't built enough to sound good on their own.

Ben

 

I LOVE the sound when im sitting inside my car. If its in the garage though, I cannot be in the garage when its started cus its LOUD.

 

Do you like the way it sounds with open headers? If so I would think you would like it with straights on it also. What kind of power are you making anyway?

Ben

 

straight pipe sounds ghetto and nasty, you like the fact that when you let off it backfires and pops? or do built motors not do that

 

Im running approx. 1000 hp. and 950 lb's tq.

 

holy

 

Actually, I believe a lot of that comes from the air pump(emissions). I really couldnt tell you for sure but I think that that will still be there some even without the emissions, but I got rid of my cat and air pump when I had the 305 and it really cleared up that sound. I havent heard my car in nearing on 11 months though. It has turned into a major project. I will not exactly have straight pipes but almost might as well. I have hooker sc long tubes and am going to be running an x-pipe w/ hooker bullet mufflers. Maybe someone can answer better what that poping noise comes from, but I know my friend used to scare the **** out of people with it because he has an rs w/ 305 tbi and 5 spd. He would accelerate up into the rpms pretty good and let off real quick just as he got next to someone walking down the road. He did have a cat but no muffler. This caused quite a poping.

Ben

 

I am also looking to put a Nos Pro-Fogger system on my car. Then hopefully it'll run low-mid 7's