exhaust size

Topic: exhaust size (Read 2790 times) previous topic - next topic

exhaust size

September 11, 2009, 08:26:34 PM

i'm trying to decide on what inch exhaust to run on my car. what i have on it now are 1-5/8 primary headers going into a 3'' collector. should i keep it 3'' all the way out or neck it down to 2-1/2? it seems alot of people are still running 2-1/2 even on the more radical cars so i dont know if 3 is a little much. it wont have cats and it'll exit in front of the rear wheels.

its a 347 with about 10.5:1 and canfeild heads and a CI cam.

thanks

exhaust size

Reply #1 – September 11, 2009, 10:03:45 PM

I'd stay 3" to keep good flow. with my setup I went with the 3" to 2.5" reducer since its pretty much a stock HO.

exhaust size

Reply #2 – September 11, 2009, 11:12:04 PM

If you want to make power: 3". I'm pretty sure you've been on sbftech.com and seen the myths and rumors section. It's been beaten to death over there.

If you want quieter: 2 1/2".

I have 3" on my 347 and 2 1/2 on the S/C 306. The 347 sets off car alarms (but there are no tail pipes on it).

exhaust size

Reply #3 – September 11, 2009, 11:56:40 PM

Stay with the 2.5 inch, it's big enough for any small block. Also you can get good buys on Mustang syetems already set up nicely to this size.

TED

exhaust size

Reply #4 – September 12, 2009, 02:52:51 AM

ive heard 88turbo's car ,,i like his set up sounds mean

exhaust size

Reply #5 – September 12, 2009, 07:55:24 AM

i'm not worried about buying a kit. the shop i work at makes custom exhausts. plus it'll dump out the sides, not really kits for that. just didn't know if 3 was too much. also, im trying to decide between a magnaflow round ler or a borla xr1. im mostly conserned about how good it sounds not really sound level. any expiriences?

exhaust size

Reply #6 – September 12, 2009, 01:03:03 PM

How good it sounds depends on each engine and the cam used, it's very hard to say. What "sound" are you looking for? I had an engine with a big cam and it was loud and mean sounding. Then I went to a stock engine for a while and the exact same exhaust was very mild sounding. Now I'm back to a mean engine and a mean exhaust.

When he puts side dumps on your car can you post a picture to see how he does it and how it is bent? I currently have dumps at the front of the axle and cannot seem to figure out how to bend the pipes to be side dumps, flow clean, and miss everything to give good ground clearance. I think you can get lers that inter and exit in the same end and may this is what they will use?

Will your local shop put on an exhaust for you without cats? This is the main reason I went to the kit. Also the kit has mandrel bends that most local shops cannot do. A 2.5 inch mandrel bend system is equal to a 3 inch crunch bent system in my mind. You can buy the kits from Summit or Jegs and do the work yourself and save a good bit of money.

Recently I ran a 11.4 quarter with 2.5 exhaust. Would it have been faster with a 3? Who knows.

Good luck and have fun.

TED

exhaust size

Reply #7 – September 12, 2009, 03:48:18 PM

Ask jay allen. What intake are you running? He was going to run a 347 with 3.5" ovular exhaust. I know which one will be faster from what I read.

exhaust size

Reply #8 – September 12, 2009, 05:15:53 PM

yeah i know it will differ from engine to engine, but a rough idea would be nice. if every had replied with 'i never heard a car with borla sound nice' then i would not buy the borla or vice versa.and yeah i can take some pics when its done.

and its a trickflow track heat

exhaust size

Reply #9 – September 12, 2009, 07:39:11 PM

I think you would be killing it with the 1 5/8" primaries. You should probably go with 1 3/4 or bigger. If your not going to upgrade headers, I doubt there would be any point in going with bigger then 2.5". I really think you should step it up a notch or two. What did you put on your build sheet?

exhaust size

Reply #10 – September 12, 2009, 09:15:33 PM

Quote from: Haystack;290963

I really think you should step it up a notch or two.

what do you mean by that?

yeah, i know 1-3/4 would be better, but when i saw they were hella expensive compared to 1-5/8, these seemed good. and i had a hard enough time getting these to squeeze in there, i cant imagine what it would be like if they were bigger.

exhaust size

Reply #11 – September 13, 2009, 02:49:09 AM

I was just saying, you have really good heads with really good intake, and then your gonna put restrictive exhaust on it. I'm not trying to come acrossed in a mean way, but if I had that much money into a setup, I would try really hard to get the most out of it I could. But times are tough right now, and sometimes you have to use what you have. Just remember though, you don't have forced induction, and your engine is quite a bit bigger then a 302. It is going to need more air, both in and out, then a 302.

exhaust size

Reply #12 – September 13, 2009, 10:46:40 AM

yeah i realize that. but these where cheaper and easier to put on. if i find myself unsatisfied with these or end up saving some money i can always get bigger and change them out. i went all out on the motor cause thats what counts most to me. its tough to change the headers on this, but not as bad as a cam. and its kinda too late now, it'd be just as tough for me to change it now as it would be in a year or two. so i can wait

exhaust size

Reply #13 – September 14, 2009, 02:07:14 AM

Fair enough. So you about ready to get it running? You going to be able to hit a track?

exhaust size

Reply #14 – September 14, 2009, 03:57:05 PM

it runs. sounds real mean. its a little on the rich side. hopefully the exhaust will help some cause i've heard running open headers can change the way they run since there is absolutly no backpressure. when its in the shop i'll pull some koer codes. i did a koeo test and all i got was a 95 secondary fuel pump wire, but thats supposedly not going to affect the way it runs. but yeah, sounds real mean