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Best choice for exhaust on 700+HP BBC

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Discussion Starter · #1 · (Edited)
Hey guys,

Got the trans build and the converter ordered, so the next item is the exhaust. I have been thinking 2 or 3 ways on this and would like some opinions to help settle on a solution.
This exhaust has to deal with a 700+ HP 505 CI BBC turning 7000 RPM

I was first thinking 3" H-pipe kit because it would be the easiest and then run some cut outs off the collector that would eventually be electric for when i needed extra flow. I am using standard deck headers with a tall deck block and the pipes will be very close to the floor board so ground clearance should be a non-issue. This is the cheapest but im not sure how much performance is given up on my application with the 3" H pipe.

Then i was thinking 3" X-pipe kit for all the same reasons as above with the additional benefit of even less back pressure? while making it a much more difficult installation and having less ground clearance.

Then i was thinking of using a 3.5" pipe/mufflers with a homemade H-Pipe/X-Pipe. The way i understand it is anything over 3" wont see much benefit from a H-Pipe especially in the noise reduction department. This way i dont have to run dumps and the exhaust would flow all i need without modification. On this kit i also planned to use the dynomax diffuser cones in the turn downs ( supposedly drops 3-5 db with very little flow loss ).


If anyone has any experience or opinions on which to run and at what point i get into over kill please drop a line or two. Im trying to achieve maximum performance without attracting those unsavory Law types ;)
 

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I have a 3.5" full exhaust exiting at the rear bumper on my 72 monte.

It has flowmaster 2-chamber mufflers and 3.5" electric cut-outs, no cross-over pipe.

I went with this size for visual impact and the fact I'm looking at a goal of a 1,000 hp...right now I'm just over 500 hp.

At the track I see no difference with the cut-outs, open or closed due to pipe size. I mainly bought those to open at cruise events and other.

I also have 3-chamber exhaust inserts that slip into the exhast tip and bolt in with one bolt...making it quite a bit quieter thus long hauls are more tolerable. I can unbolt and remove both of them in a couple minutes. I have run these at the track and my ET's are 1/10th slower...but makes city driving feel more peppy, definately changed my torque curve from the back pressure.
 

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Off the 3 1/2" Hooker header collectors with 3" H pipe thru Dynomax welded oval race mufflers to 3" dumps at the rear axles used here. Never been uncapped.
Works fine but planning on full tail pipes very soon to avoid the dust blown up by the dumps.
 

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Maybe this will help you make a decision.A friend of mine put 5" on a 67 Camaro with a 522 that made 988hp.at the flywheel on nuts.Wonder what the power will be when the two stage Fogger comes on.
Think that's crazy,he's running a 10.50W tire!
 

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3" and H pipe..dynomax super turbo's. just ordered the UltraFlo's. If you decide on 3.5", just get 3.5" connectors to 3" tails.
 

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Discussion Starter · #9 ·
Off the 3 1/2" Hooker header collectors with 3" H pipe thru Dynomax welded oval race mufflers to 3" dumps at the rear axles used here. Never been uncapped.
Works fine but planning on full tail pipes very soon to avoid the dust blown up by the dumps.
Thanks Bill,
This is exactly what i was thinking. Using DynoMax ultraflows or split flows and the rear turn down at the axle. Im definitely not going over the axle.

Shawn
 

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Discussion Starter · #10 ·
3" and H pipe..dynomax super turbo's. just ordered the UltraFlo's. If you decide on 3.5", just get 3.5" connectors to 3" tails.
So your saying use 3.5 pipe and mufflers then reduce down to 3" after the Muffler? BTW i was planning on using the Ultraflo's let me know how they sound for you.


Shawn
 

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Maybe this will help you make a decision.A friend of mine put 5" on a 67 Camaro with a 522 that made 988hp.at the flywheel on nuts.Wonder what the power will be when the two stage Fogger comes on.
Think that's crazy,he's running a 10.50W tire!
What has the car run so far and at what weight and gear? Sounds like its a bit big on the exhaust size.
 
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