switching from the crappy 2.5" single dynomax super turbo cat back to hooker 3" catback....wondering if anybody would guesstimate how much more power I am gonna be rewarded with just changing the catback with my mods?

with the mods u have u will prob pick up 15hp bc of the HSR and the RPM range which is limited by the 2.5" system. u might even want to look up a 4" system bc ur motors puttiing out around 400 crank hp... which is the max for a single 3" system.

yeah i am at the inbetween needing a 3" and 3.5" or 4" exhaust....i know whichever i choose its gonna be wrong!

Hi!
I answer becouse i am in the same possition whit almost the same mods exept stroker.
I was thinking of long tubes hooker headders and 3"collector and a "H"dual cat 3" exhaust,maybe that is to much for a 350-400 hp crank engine.

well...custom exhaust place wants about $450 for a 3.5" hooker exhaust and only $350 for single 3"......unless the half inch is gonna boost me up like 20 more hp.....i dont think im gonna go 3.5

dual 3" exhaust is way to much for a 400hp crank motor. im gona barely use it for my 500hp+ crank motor, but a procharger will take care of that )))

you could use dual 2.5 inch.. thats what i run.. my specs are in the vBGarage.. dual 3" will be too large.. as will a 4" single.. 3" single should be fine.. should pick up at least 10rwhp.. maybe more.. if that custom exhaust place can do a 3.5" single, that would be perfect.. just make sure you have a good muffler too..

after some calculations, a single 3.5" will give you 96% more cross sectional area as a single 2.5".. a dual 2.5" will give you 100% more flow obviously..

but is $100 or more worth the extra power I will be getting from going 3.5 rather than single 3? thats the question
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with that in mind...how much more cross sectional area will a single 3" have over the dynocrap on there right now
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i think 82%?

No way to really know the horsepower gain. However I would not hesitate to go with the 3.5" exhaust.

I'm running the 3.5" Mufflex exhaust with my 355 and I'm putting down 12 more rwhp and 14 more rwtq than your 385. This is with a modified TPI. So the answer could very well be in the exhaust.

Id say toy can see 5-20 maybe, depends.

well that dyno tune was done on a slipping transmission (very badly slipping), and a non lockup converter. after the tranny was rebuilt, it felt ALOT better.

I forgot some key information. Between dyno runs I intalled a Meziere electric water pump and the Mufflex 3.5" exhaust. I would have to check to be exact but I pick up like 22rwhp and 26rwtq. I would have to say that maybe 15hp and 17 torque was from the exhuast. With your 383 it should do better with the 3.5" exhaust.

now i am toying with the idea of going to slp 1 3/4 headers, single 3"in 3"out cat and 3" catback (hooker header muffler or magnaflow)