GM-DR wrote:Probably should let everyone know your motor/car combo first. On my car 3400# 355 9-1 motor appx 400hp I have yet to find a better collector than the flowmaster this is 1 3/4" primary tubes and 3" collector opperating between 5000-7000 rpm and I have tried several.
Brktracer wrote:Good point!
421 SBC. Pretty much the standard race set up. 14:1, 273/280 roller, Track 1 CNC. 5300 converter, roughly 3000 lbs '69 Camaro. 1.89 glide, 4.30 gears, 29X12 tires. Usually runs in the 6.3-6.4 range. 1.43 60'.
How are your tubes paired with the Flowmaster collectors? What difference did they make?
Ron Golden wrote:On one bracket 406 SBC with "average" (13/4x 28 x3) headers an 18" extension picked up 96 lb/ft of TQ @ 4500 rpm. I didn't believe what I was seeing so I did back-back dyno pulls and confirmed the results. All the TQ numbers increased below peak TQ and gained about 1% of HP.
On a 438 FE Ford street engine the increase was 51 lb/ft at peak TQ...no HP increase/loss.
I finally started throwing a long extension on almost every engine I dynoed and saw the TQ increase every time.
I added an 8" extension on one engine and lost TQ. The long extension increased TQ.
Not very scientific but it certainly opened some eyes and got people to thinking about the energy in the exhaust system.
Ron Golden wrote:Z28,
If my memory serves me correctly I didn't even retune most of the engines for the long collector, just stuck it on to see what it would do. I'm sure some additional gains could have been realized if I had played with the length and tuning.
Vizard did some dyno testing on headers and wasn't too concerned with primary length but concentrated on collector length. He said a primary variation of 9 inches was acceptable. I know David is a lot smarter than I am so I have to take him at his word. Great guy!
Barry_R wrote:On my FE EMC stuff I have tried a bunch of headers - especially when we were required to run a "production" header that fit a vehicle. In simplistic terms I found that the really wide RPM range largely negated the benefits of one header over another one to an extent - but that getting collecter length right was comparatively huge and always positive.
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