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mr1974gto 08-19-2007 07:59 PM

Flowmaster Super 40
I have 2 1974 GTOs. One with a 350, 9.5:1, 288/302 with 408lift, headers and 2.5 in. pipes with super 40s. The other has a 455, 9.0:1, 301/313 with 470 lift, headers, and 3 in. mandrel bent pipes with super 40s (that I just put on this weekend). It seems as though the 350 is louder than the 455. Also my dad has a 1967 gto with a 400, 11:1, 301/313 with 470 lift (same cam as 455), stock manifolds and 2.5 in. flowmaster super 40s and its even louder than both mine. Anyone know why this could be? compression maybe? Thanks for any info. :confused:

mr1974gto 08-19-2007 08:08 PM

Fuel pump
Also I have a Holley black electric fuel pump on my GTO. It had open headers until this weekend so I never really noticed how loud the pump was. I bought the pump used a few months ago, the pump works great its just really loud. With the new 3in flowmaster exhaust, setting in the car I can hear the pump as much as the exhuast. Is it normal to be that loud or is my pump fixin to take a **** on me?

Blazin72 08-19-2007 08:25 PM

I think you answered your own question. I have Super 40s on my 72 Blazer and the exhaust is identical (headers, pipe size, mufflers) to a friends 71 3/4 ton Chevy. Both are 350s but my engine makes twice the horsepower and is significantly louder. Furthermore, the exhaust got even louder after I installed a small blower.

mr1974gto 08-19-2007 08:36 PM

I think my 455 makes more power just less compression. does compression make that big of a difference in exhaust sound?

454C10 08-20-2007 08:20 AM

A lot of things can effect exhaust sound. Cam timing, rod/stroke ratios, cylinder heads, cr, pipe shape, pipe diameter, pipe length. ect, ect.

Yes, holley pumps are super loud. I hate them with a passion. Get a mallory comp110. They are quiet as a church mouse and can handle a 450hp engine. The mallory comp140 with regulator can handle a 600hp engine.

Flow masters don't flow very well when considering how much noise they make. A OEM like Dynomax Super Turbo out flows a Flow Master and does it at under half the volume. That is the sign of a good muffler (good flow and good sound reduction). Flow masters just came up with a great name for their loud **** mufflers. Hooker-areochamber's have great flow (50% more than flow masters) but are louder than the Dynomax's but still 25% quieter than the flowmasters.

454C10 08-20-2007 08:23 AM

check out this muffler flow site.

jimfulco 08-20-2007 08:58 PM

I think smaller engines tend to be a bit louder than a larger one with the same system. My '69 & '72 Novas have exactly the same exhaust systems, stock iron manifolds with stock-type Midas dual-crossflow mufflers, and the '69 was noticeably louder with a 283 than the '72 with a 350.

How's that 068 work in the 350?

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