lets talk exhuast size and how it effects note.

i built my pipes for my plymouth yesterday. i got them to just past the trans cross member do to i dont have my mufflers yet. I had no choice but to use 1.5" pipe. my frame is very narrow and the clutch and shifter linkages take up much of the same space as the exhuast. now im using a chevy 250 six with the stock split manifold. i would like to run either a cherry bomb or a smitty muffler. but of course they only come in 2" or bigger (for the bombs at least)so i will have to step it up to go into the mufflers.

Now from what ive heard and seen back in the day most people ran this small of pipe. (im talking way back). and when i first got the herpie is had split manifolds on a 216 going straight into lakes pipes and those are around 1.5" it sounded like a bi-plane, i loved it.

now with using a glass pack about mid way of the system would i have a more mellow tone? i want to drive this car long distance and dont want it to loud but i want to still be able to rap the pipes ya know.

and what ill effects may i see my using 1.5" pipe. (keep in mind the stock Y pipe on the donor truck was 1.5" as well) my thinking is dual 1.5" will be pleanty of flow for this little 250.

Thanks
Bryan

 

Inch and a heif aint bad. I had always been told a smaller pipe provides a healthier rap. As well as keeping the glasspacks as far forward in the system as possible. I have 1 3/4" on the 289 in my ford from the manifolds back. The glasspacks are under the front floorboards and its 2" back from there. The packs are only 6 inches long and burned out to boot and its loud as hell. Real good rap too, won plenty of muffler rap contests. Even had a guy blow his motor trying to beat me. Some hopped up Camaro or somehting with flowmasters.

 

I've only delt with V-8's but what I know is...
Smaller diameter pipe will give you a "rappier" tone but will obviously restrict air flow. Larger pipe will give you a smoother tone but can cost you some bottom end torque if you go too far.
The closer to the engine the mufflers are, the higher the exhaust tone.

 

that's exactly right. smaller pipe = more rap or cackle in the pipes.
larger pipes = more of a throaty sound, or rumble.
keep the mufflers as close to the manifolds, or headers as possible to get the best rapping noise.
i found that if you use long tube headers (on a 350 for example), and then get the glasspacks that bolt right to the header flanges. run 2" pipe all the way back to the rear of the car from there...will produce one hell of a rapper.

 

I just put dual smittys with 2" aluminized pipe throughout on a 472 caddy and it sounds perfect. I mounted the smittys about center
just because there is no room under the car, plus plans call for bags. But it sure has that perfect mellow 60's tone/rap idleing and when rolling down hills ect...But as soon as you punch it it really comes alive. Oh yeah dirty the companys just say 2" inlet/outlet for the packs usally they are bigger than 2" depending on who you use just get with the seller and have them measure first and you can crimp them down..This is so you can slide the pipes in easier

 

I went the other direction with my stepdown 49 Hudson. 308
Hornet motor into split tube headers,then 2.25"pipes all the way
to the back with glasspacks and tips at the end. The stepdown
chassis doesn't give much option for muffler placement,just getting
both pipes under it was a job. Not gonna win any pipe rapping
contests, but it works for me. Barks when I want it to,but livable
on the highway. I figure with the bends and clearancing on the pipes
its effectively close to a 2" pipe.

 

cool, i want that rappier tone so im headed in the right direction. the mufflers will be about 3 foot behind the manifolds with straight tail pipes the rest of the way back(i have to go under the axle do to my car laying the frame on the ground). i thought about putting about 1 foot of 2" on the ends so it doesnt look so sad with 1.5" pipes comming out the ass end.

 

easier way out - chrome tips that neck down to 1.5- and have a 2 or 2.25 outlet. they would act like a mini Echo chamber- amplifiying the "slap", but keeping the actual note managable.

 

I wouldn't go smaller than 1-3/4" for a chevy 235 or bigger.
That size is great for driving around town around 2000rpm.
For the freeway you want 2" pipes for that size engine.

The smaller diameter pipe helps low end torque and the exhaust tone gets brighter and higher in pitch.

Pipe size selection is mostly about rpm you drive most of the time, muffler length and type is more about sound.
Longer straight tail pipes give more rapping.
Uneven length pipes also make more noise at deceleration.

If engine performance doesn't matter and sound is more important, just experiment with a few extreme setups and get a feel for pipe size, length and different mufflers and tips.
In the end, only your own ears and personal experiments will give you the exhaust you want.

 

O ya, and mine has 4" cans out the back of the 2 inch. Homemade from a big diesel truck exhaust stack. Great for flamethrowers and sound.