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Topic Review (Newest First)
10-29-2012 11:09 AM
cobalt327 Big engines are sensitive to restricted exhaust flow. On a Pontiac 455 in a 4x4 Blazer that the dude insisted on using the column shifter, I had to use factory exhaust maniifoolds. It literally KILLED that engine! I bet it loped off a hundred HP and that much torque to boot!

On the same engine I had used 3" Flowmaster 40's w/an H pipe connecting the two sides. Had turndowns about a foot long out the back of the mufflers. They ended right under the rear seat area.

This was in an '81 Camaro. You'd have thought the droning would have been bad- and it probably would have been, had I not used heavy factory-type insulation (tar/felt type) scavenged from junkyard vehicles.

About the best thing that could be said for it was it wasn't very restrictive. But it would set off car alarms just idling through a parking lot- which was something I enjoyed doing where the ricers congregated in the K-Mart parking lot on W. Colonial Dr. in Orlando on weekend nights. Not so enjoyable while driving through residential neighborhoods, like my own.

But it ran great. Effortless 12's w/a 3.08, lower 12's w/a 3.31 rear gear.

Check out Cliff Ruggles: Cliffs High Performance Quadrajets :: Qjet Carburetor Rebuild Kits, Parts, Quadrajet Rebuilding, Quadrajet Parts, Bushing Kits, Carb Tuning

That said, no good reason you can't tune the Edelbrock 750 to work. I don't much care for the non adjustability of the secondary opening rate, unless it's a Thunder series carb.
10-29-2012 08:26 AM
bigdog7373 Turbo mufflers on a 3 inch sytem behind a big motor like that sound absolutely amazing. I guarantee you will love the sound.

The 750 edelbrock is perfect by the way. Best street carb out there imo.
10-28-2012 02:58 PM
billonwheels Whats wrong with the Edelbrock? I've had people say Holly, haven't heard of Cliffs.....
10-28-2012 02:34 PM
Bonneville462 I went through a pile of mufflers on my Pontiac 455 (462) until I tried the Magna Flow #12640..

If you want better performance, try a Cliffs Quadrajet with a stock Iron Quadrajet intake.. That carb isn't the best for your set up....
10-24-2012 11:03 PM
vinniekq2 noise level will also be affected by power output and cubic inches.Aluminum heads make a different sound than cast iron.ported heads sound different
10-24-2012 10:46 PM
S10 Racer Keep in mind that Flowmaster has 5 different series of mufflers, each with their own sound level. Google it and find out what you want.

1. Super 10 -The loudest of the five, close to open exhaust.
2. Super 40
3. Super 44
4. 50 Series Delta Flow
5. 70 Series - Quietest of all of them with a mild tone
10-24-2012 09:31 PM
billonwheels Seems like Flowmaster is what everyone's using. I don't have anyone around here with Magna Flow. Any sound diffrence between the 2? These Glass Packs got to go....
10-24-2012 08:54 PM
hcompton
Quote:
Originally Posted by vinniekq2 View Post
buy a 3 inch system and get the mufflers as far back as possible. I use an X pipe for sound,its a lot quieter than true duals
Not so easy on a gp the motor really far back and very low in the chassis trans and drive shaft are in the way for crossover. I am not sure if anyone makes a bolt in system for that car 3" crossover.

3" i totally agree. Flowmastwr for me was a quick fix. I was shocked at the quality when i opened the boxes. Sales dude at jegs new what i needed and got me everything including clamps and turndowns in one shipment. He had a monte.
10-24-2012 08:39 PM
vinniekq2 buy a 3 inch system and get the mufflers as far back as possible. I use an X pipe for sound,its a lot quieter than true duals
10-24-2012 07:11 PM
techinspector1
Quote:
Originally Posted by S10 Racer View Post
Thats a typical problem with the old glasspacks. The back pressure they cause (somewhere around 15-18psi) is robbing power from the motor. A good quality muffler like Magna Flow, Walker Ultra Flow, Thermal, A'PEX, Borla, etc. are good low back pressure mufflers. Any of these will only cause about 1-2psi back pressure. It's not the tuning, it's in your mufflers.
Please show your references for these data. I'd be very interested in reading it.
10-24-2012 06:40 PM
billonwheels Thanks, Still working on it. Pontiac excitement!
10-24-2012 06:37 PM
hcompton
Quote:
Originally Posted by billonwheels View Post
I'm going with dual exhaust next week so the glass packs are coming off, it was just a quick fix. Magnaflow was on my mind. want a diffrent tone than the typical Flow master.
Go big 2 1/2 at smallest. Those engines love to breath. I did 2 1/2 and it made good power. Hard to beat an exhuast that makes the same power as open headers as far as my butt dyno could tell. Felt faster actually. Sound was loud it would shake the ground like open headers. Neighbors hated it. Didnt sound anything like a mustang with flowmasters.
10-24-2012 06:24 PM
hcompton Love the car i had almost the same setup. 71 gp sj 455 ho 472. Edelbrock heads built block. Same issue with old exhuast car was flat. Installed flowmaster dual kit with 40 series. It made as much power as open headers. Think i got a kit for a g body and some extender pipes and it was bolt on. Mufflers in front of the rear end.

Glass packs always kill power. They have onthe to cars i tried them on.
10-24-2012 06:19 PM
billonwheels I'm going with dual exhaust next week so the glass packs are coming off, it was just a quick fix. Magnaflow was on my mind. want a diffrent tone than the typical Flow master.
10-24-2012 05:56 PM
S10 Racer Thats a typical problem with the old glasspacks. The back pressure they cause (somewhere around 15-18psi) is robbing power from the motor. A good quality muffler like Magna Flow, Walker Ultra Flow, Thermal, A'PEX, Borla, etc. are good low back pressure mufflers. Any of these will only cause about 1-2psi back pressure. It's not the tuning, it's in your mufflers.
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