What is it that makes one carb have that wonderful deep sound at WOT, and another one not? My '88 Gran Fury (old cop car)with the factory 318/Quadrajet was music to my ears when I floored it. Nice deep sound I grew up loving! The 360 crate motor I put in has a Holley 750 #3310, and does not come close to sounding like this. Same air cleaner is run on both. I want that sound I love so much. Thanks.

Think of an engine as being an air pump. A car with a free flowing exhaust will likely have less carb noise. The restrictive exhaust causes the fuel and air to resonate longer in the intake tract. I've seen the Diplomat/Gran Fury cop cars... 2 pre-catalytic converters, a y pipe into a single pipe, ANOTHER cat, then a muffler. Certainly NOT a free flowing system by any measure. Another reason... The Quadrajet is a spread bore carburetor with secondaries LARGER than the Holley. If you tried each carb on the same motor, the Q-jet would make more noise.
Finally, the cam timing in the crate motor is surely more aggressive than the cop spec 318. That will affect things too.
I have a cold air kit in my 2007 ram with the HEMI. It ROARS compared to the stock setup. If I ran it without catalytic converters, it would certainly be quieter.

Ok, i can understand that. One thing, I did have a catless exhaust on the cop car prior to the engine swap. But I see what you are saying. I guess the combination of spread bore vs square bore and other factors. Too bad. I sure love that sound. thanks.

Removeing cats makes the exhaust louder, it does not quiet down the intake. The reason you carb made that wonderfull sound was the size of the secondaries, think of it like the pipes on a pipe organ, they make noise by air blowing across them, the little ones make higher sounds and the bigger ones make bigger lower sounds. If you really want to here that sound get a thermoquad, they have the biggest secondaries and run an open style air cleaner. As a bonus you will get better MPG with a t-quad than a holley.

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The 360 has a square bore intake...can I get a thermoquad for square bore, and will it still sound as good? thanks.

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Define "good" and I'll answer you

The air valve in the TQ's and Qjets probably helps with the sound.

Spread bore carb will give you the "Big sucking sound" you like. Depending on what intake you have, you may be able to make it work. LD340 intakes (maybe others???) were made "as cast" for square bore carbs, but they also cast the flange area with enough extra meat that it can be hogged out to work properly with a spread bore carb.

My 360 has the MP M1 Dual Plane. I guess I will have to live without that sound, at least for now. I guess each intake (spreadbore and squarbore) have their benefits and shortcomings. What is the shortlist? Thanks!