Cheap Speed - Catback mod

[chuckspeed]

Guys-

If you like droppin' $400 for a catback, then read no further. If you're like me and want cheap speed - read on:

It turns out modern exhaust systems are much better than their earlier brethren. Even the F-body single pipe system handles the flow reasonably well, and the basic systems are good - SS pipes, mandrel bent tubes.

Rule of thumb: A 2-1/4' pipe is good for 175 HP, give or take a few. A 3" single pipe will flow 320 HP fairly easily. So...Unless you're building up 400+ NA HP, stocker pipes will work just fine.

The 'trick' is to eliminate the restriction of the muffers. This can be done in most exhaust systems by cutting out the stock muff and welding in a glasspack muffler.

Glasspacks are extremely durable and are essentially wide open perforated pipes. They have similar pressure drops to straight pipe, so you lose a LOT of backpressure when putting in a glasspack. On Mustangs, there is a drop-in muff available - I have the P/N in the garage. On single inlet/dual outlet F-bods, you'd have to 'live' with a single tip - if I recall, the first late-model SS's ran a large single tip on the driver's side.

I don't like makin' HP claims, but the gain would be similar to what catback manufacturers claim - and you get the neato glasspack sound. It's quiet at first, but when the fiberglass mats up - you get a killer burble when you're foot is in it.

Cheap? Hell yeah! Glasspacks typically run less than $20, which means you can do a dual exhaust system for less than $50 On smaller displacement motors (like 4 cylinders), a pair in series really drops the tone - I have this setup on my wife's PT Cruiser. Quiet 'round town and not raspy like the fart-tip crowd.

NEXT: Cat converter mods...

[WishIHadACamaro]

This is something i should do to my liberty.

The muffler is a friggin monster, and i can only imagine what kind of horrible backpressure is created due to this.

[jdustu]

i like cheap...i like fast........i hated the sound my z made when i got it(crappy y, no cats, slp single in single out muffler) so i cut off the muffler with a sawzall....after a while i bought a purple horny for less than 30 bucks and welded the clamping end of the i-pipe to the inlet end of the glasspack and ran a longer bolt through the rear seatbelt and hung it on that......then i got used macs and and ory with dual cutouts for 250 shipped from texas and put that in front of the glasspack........cheap...fast(gained .6 and 5mph with a rear swaybar, no back seat, and the open headers)......and LOUD!!!! i like the idea of getting an underdrive pulley made :smt017 i'll have to talk to a friend at work.....

[Billster]

Originally Posted by chuckspeed

Guys-

If you like droppin' $400 for a catback, then read no further. If you're like me and want cheap speed - read on:

It turns out modern exhaust systems are much better than their earlier brethren. Even the F-body single pipe system handles the flow reasonably well, and the basic systems are good - SS pipes, mandrel bent tubes.

Rule of thumb: A 2-1/4' pipe is good for 175 HP, give or take a few. A 3" single pipe will flow 320 HP fairly easily. So...Unless you're building up 400+ NA HP, stocker pipes will work just fine.

The 'trick' is to eliminate the restriction of the muffers. This can be done in most exhaust systems by cutting out the stock muff and welding in a glasspack muffler.

Glasspacks are extremely durable and are essentially wide open perforated pipes. They have similar pressure drops to straight pipe, so you lose a LOT of backpressure when putting in a glasspack. On Mustangs, there is a drop-in muff available - I have the P/N in the garage. On single inlet/dual outlet F-bods, you'd have to 'live' with a single tip - if I recall, the first late-model SS's ran a large single tip on the driver's side.

I don't like makin' HP claims, but the gain would be similar to what catback manufacturers claim - and you get the neato glasspack sound. It's quiet at first, but when the fiberglass mats up - you get a killer burble when you're foot is in it.

Cheap? Hell yeah! Glasspacks typically run less than $20, which means you can do a dual exhaust system for less than $50 On smaller displacement motors (like 4 cylinders), a pair in series really drops the tone - I have this setup on my wife's PT Cruiser. Quiet 'round town and not raspy like the fart-tip crowd.

NEXT: Cat converter mods...

:smt025 Sounds cool! I'd like to try it with my 06 GT! You think I'd need to retune for the more open rear?

[defln67]

i just cut the the glasspacks off my car, 20 summin bucks. everyone thought i had flows til reved it and it made a loud bang, there worth the money, i had cherrybomb glasspacks. . .