454 BB chev-GQ exhaust system??

Post by **gq351** » Wed Jul 16, 2008 1:00 am

hey guys ive just fitted a new mild 454 bb chev to my GQ lwb, im just finishing of bits & pieces & need a exaust system done soon,
just wondering what would be a beter choice a good single 3'' or twin 2.5 ?
i want it to get a good flow without being resticted & sound tuff.
any ideas would be great..
thanks jess

Post by **Hoonz** » Wed Jul 16, 2008 10:05 am

twin 3"

twin 2.5" = 5" of flow
single 3" = 3" of flow

Post by **chimpboy** » Wed Jul 16, 2008 10:29 am

twin 2.5" = 9.8 square inches of pipe opening

single 3" = 7 square inches

I would think both options are going to sound pretty good.

Post by **jessie928** » Wed Jul 16, 2008 11:35 am

gq351 wrote:hey guys ive just fitted a new mild 454 bb chev to my GQ lwb, im just finishing of bits & pieces & need a exaust system done soon,
just wondering what would be a beter choice a good single 3'' or twin 2.5 ?
i want it to get a good flow without being resticted & sound tuff.
any ideas would be great..
thanks jess

twing 2.5 inch pipes along side eachother.
when you run them together out the back, the exhaust note sounds much better

JEs

Post by **bogged** » Wed Jul 16, 2008 12:13 pm

single 4inch sidepipe, no muffler

Post by **brettsGQ** » Wed Jul 16, 2008 1:05 pm

im guessing twin 3inch my mate had twin 2.5 on his mild bb and it was restictive he put it on a dyno and it made 300 hp at the tyres and then he put the twin 3in on it and put it back on the dyno and it made 320 hp at the tyres its just a matter if you can fit twin 3in out of the patrol side by side or each side

Post by **stool** » Wed Jul 16, 2008 7:15 pm

Jess do you need some part numbers for standard style GM headers.

Or are you going custom extractors.

That was a quick install mate well done

Post by **gq351** » Thu Jul 17, 2008 11:17 pm

thanks alot guys i was thinking more so twin 2.5, do u think it would sound better both running out the same side?
or right & left?
thanks

Post by **gq351** » Thu Jul 17, 2008 11:23 pm

stool wrote:Jess do you need some part numbers for standard style GM headers.

Or are you going custom extractors.

That was a quick install mate well done

hey steve, dont worrie mate im not that quick its all bolted in but im still doing all the little fidely shit which will still take some time.
yeah im gonna use the standard manifolds for now coz there isnt much room on the drivers side,
i think the pair i have should be ok but ill let u know if i need the part numbers,
hows yours going??
thanks steve

Post by **stool** » Fri Jul 18, 2008 7:21 pm

I drove it home from the gas installer yesterday and its
quicker than my brothers EL`xr8

Just got to mod the exhaust around the gas tank than its rego time

Post by **BowTieGQ** » Sat Jul 19, 2008 10:18 am

I too want to go two 2.5" but not sure how to get rh side around transfer. I also want to run two small lpg tanks either side. Like the ones that are used for diesel/gas. How did yours route and what did you end up getting?

Post by **gq351** » Sat Jul 19, 2008 1:11 pm

i havent got mine done yet coz ive still got little bits & pieces to finish off, but i think ill go twin 2.5 but cross it over before the transfer case, but im not sure to run them both out the left together or one pipe on the
drivers side?
ill let u know when i get it done

Post by **BowTieGQ** » Sat Jul 19, 2008 6:26 pm

My latest thinking is to only run a second little lpg tank on the drivers' side where my petrol tank is now. Then run the two 2.5" together on the passenger side and exit together. Performance is the reason I want two 2.5" and not a single. Chevs work better with that. Holdens better with a single, being smaller capacity. Plus twin sounds better, even if they are next to each other. Oh well. Would also allow for an air tank next to exhaust too for on board air. But let me know anyway.

Post by **gq351** » Tue Aug 12, 2008 10:30 pm

BowTieGQ wrote:My latest thinking is to only run a second little lpg tank on the drivers' side where my petrol tank is now. Then run the two 2.5" together on the passenger side and exit together. Performance is the reason I want two 2.5" and not a single. Chevs work better with that. Holdens better with a single, being smaller capacity. Plus twin sounds better, even if they are next to each other. Oh well. Would also allow for an air tank next to exhaust too for on board air. But let me know anyway.

hey BowTieGQ, my gq's at the exaust place at the moment so i should pick it up on friday,
im getting him to do a twin 2.5''inch twin system with a cross over section into two mufflers & to exit one pipe each side, i should start it up next week to bed in the cam, so ill let you know what sounds like

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