What inlet/outlet size mufflers?

['70 C/10 SS500]

My '76 500cid Caddy motor is getting ready to find it's new loving home in my '70 SWB truck. If I use midlength headers, what size head pipes (dual pipes, exiting at rear of cab door out the under/side) should I use and what size should the inlet and outlet i.d.s on the mufflers be? Mid-lengths are about the best headers commercially availible (that I know about) for the big Caddy motors without having to fab up customs or midify BB Chevys to work. My truck is soley for street fun, no highway, no off road, no strip duty. 4.88 rear gears should help multiply torque as well as give new hope to tire shops in this uneasy economy! RPM, well, my right foot will have to manage that with those gears. Here's to stop lights and signs to keep me honest, and away from catastrophic motor failure. If I REALLY HAVE TOO, I'll re-install my 3.73s. No need to reply to that, let's stay focused on the exhaust.

So, what size pipes and mufflers will have a rumble that will shake the colagen out of your skin from 100 yards away? Low end Torque? I like it as much as everyone else, but with 500 cubes and 4.88s I'm not to worried about that in regards to pipe selection considerations. I really think that overall, the sound of the motor is what MOST concerns me, I want it to be LOUD, but not sound like a dump truck! Help me out, give me a hot rod (sounding) Caddy! Shoot those suggestions/sizes too me!

[lukecp]

I would go with 3" dual pipes all the way. You may loose a tad bit of low end....but with 500 cubes under the hood, and 4.88's out back, you wouldn't know the difference.

For the mufflers, i would go with a pair of Flowmaster 40 Series mufflers, possibly the Delta Flow varietries. They are pretty aggressive, and loud too. My mild little smallblock sounds great through dual 2.5" pipes and Delta Flow 40's. Other people may reccomend Magnaflows or something else, i like Flows myself. The best thing to do is find a really good sounding vehicle, and ask the owner what kind of muffler they are running.

[GasHog396]

I'll 2nd the 3" and Flowmasters. Check out the Flowmaster web site for all of their mufflers (Click here). You can even listen to the different mufflers to get an 'idea' of what they might sound like on your truck. A friend has 40's on his truck, a F@rd with a V6, and it almost sounds like a V8 at idle. Almost! His neighbors (they drive Volvos, nuf said) have actually complained about the noise waking them up in the morning! Those 40's are definitely towards the obnoxious end of the spectrum. I like them, but I wouldn't want to have them on a daily driver, or during a long haul.

[miket]

I put Hedman headers that had primaries just shy of 2inch's each....then with 3" pipes all the way back, h-pipe and 40 series 2 chamber flowmasters...Thats behind a ZZ502 and it's GREAT.

[Jerrys1stgJimmy]

how much more quiet are the flows than cherry bombs?

[lukecp]

I used to have 12" glasspacks (same thing as cherrybombs, different company), 2" pipes, headers, and 24x3 echo tips on my truck. It was a little quieter than my 2.5" system with Delta Flow 40's on it. Also, i don't run any tailpipes. The mufflers just end above my rear axle. When i ran turndowns on it, the flows were quieter than my old glasspacks.

It can be a bit obnioxus, i took a 4hr trip in it not too long ago, and pulling 3000rpm the whole way, my ears hurt a little bit when i was done Sounds great though! I turn heads everywhere if i give the truck a bit of throttle.

[crazy longhorn]

3" pipe wont hurt on that big caddy, but will be loud as he!! You might go 3" in, & 2 1/2" out of the muffs, & add an H pipe to mellow it a bit. I think a set of Dynomax Hemi turbos would be the way to go on that one.....she will still sound off! The 4.88 gears are way too deep for a Cad.......they have gobs of tork, but are done running around 5000 rpms. I would suggest a mid 3s gear to make the most of the combo. Good luck,crazyL