In the not too distant future I will be replacing the exhaust system on my 72 Cutlass Supreme (455). The one on it now has some issues, so it's time. It's a 3 inch system all the way back from the headers (replacing those too) with a step down to 2-1/2 to the tail pipes. I'm also consideting stepping up from the 670 Holley Street Avenger to a 750 Holley.

If I go 2-1/2 inch all the way back (Flowmaster American Thunder Kit 17119 with Super Series 40 muffers), will it be enough for the 455 with the 750 carb? I'm pretty sure the engine has a slight build, so I wanna make the right decision with the exhaust system. I'm also looking at Flowtech headers 31154FLT, so I'm hoping for a good deep tone with some rumble...

Also, with so many choices on the carb, how do I pick the right one? Not looking to make my Cutlass a stoplight warrior, just want good performance and a good cruiser.

Am I on point with my choices, or way off base?

Thanks,
Dave
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Don't buy Flowtech headers. My SBO rusted pin holes through ceramic coating within a year and needed double gaskets to seal. Get Hooker or Hedman headers. Many don't like the sound of Flowmaster mufflers and 2.5" should be fine. I loved the sound of Aerochamber mufflers on my G body, sounded amazing. The exact same system is way too loud in my 70, thinking Dynomax Superturbo mufflers.

 

Dave, I deleted your other thread. No need to have double posts.

Have you considered rebuilding the Street Avenger on your 455 now?

 

Its a new carb...670 CFM...but I keep getting told it's not enough for my 455.

 

The 2.5 inch dual exhaust will be good for your 455 along with the Holley 750. I would go with Hooker headers as the minimum price/quality choice (they fit, work and last OK).
I do not like the Flowmaster 40's- too loud. Sound great for sure, the idle rumble is terrific but the droan got to me. Replaced my Flows with Dynomax Super Turbos.

 

Hooker aerochambers sound great. With tail pipes should be nice and mellow I run aerochambers on my 355 olds full length black jack headers and an x pipe. I always suggest an x pipe. they make a big difference in power. enough to show up on a time slip at the track., but also offer a unique sound .

This the aero chambers with an x pipe and turndowns at the rear axle.

 

The Street Avenger is a great carb and is available in a 770 CFM, which should be ideal for your purposes.

 

Thanks..now I have an idea...will do some pricing.

 

Would these be a good choice?https://www.summitracing.com/parts/hok-2451hkr

 

So here's the package I picked out...
https://www.summitracing.com/cart

 

First summit post is for small block headers! The second post of what you picked is blank info post! The header you want are for a 455 correct?

 

Ok...let's try again...for whatever reason the links aren't working so here are the part numbers...

Flowmaster 17107

Hooker headers 3902hkr

Holley 0-80770 carb

Hooker aeromasters 21502hkr

 

If anyone out there would care to chime in and voce their opinions That would be great!

Thanks,
Dave

 

I like Walker Dynomax mufflers for a nice, fun street car with good performance. They are much milder and quieter than any version of Flowmaster.

If your engine is under 400hp, a 2.5 inch system will be fine. If over 450hp, a 3 inch system should be considered. If over 500hp, a 3 inch system is really required.


I have also used Dynomax ultraflow mufflers with and without an additional "bullet style muffler in line or after them to mellow them out if found to be too loud.


You will hear a lot of exhaust drone at high speed with Flowmaster 40 series mufflers, the 50 series or SUV long ones are much better, but still louder than a "turbo" style muffler.