340ci TTi Exhaust Help: 2-1/2" or 3"?

[Carlwalski]

I am needing help picking some headers and exhaust for my 340ci. I think I have the headers covered but am not sure if a 2-1/2" or a 3" exhaust is what my engine needs. I am after the most horse power I can get. I'm not worried about loudness. I have exhaust cutouts so loudness is good lol. The system will be all tti with dynomax super turbo mufflers. I have W2 heads but am not sure what kind, factory ones I think?? The engine was built by the previous owner who didn't skimp on anything so it's got some nice gear in and on it.

Which system would be best suited for the maximum performance gains using my engines specs:


A:

“W2 STEP” HEADERS for LA STYLE - SINGLE BOLT PATTERN W2 HEADS
1-5/8" O.D. primary tubes, 1-3/4" O.D. secondary tubes with 3" collectors and a 3" X-pipe Exhaust.

OR

B:

W2 / W5 1-7/8” RACE HEADERS for W2 & W5 RACE HEADS
1-7/8" O.D. primary tubes with 3" diameter collectors and a 2-1/2" X-Pipe exhaust.


My engine specs:

Cylinder Heads:

 - Factory W2 oval port intakes
 - D-Port exhaust
 - Extensive port
 - bowl and combustion chamber mods
 - Hardened exhaust valve seat inserts
 - Ferrea 2.02 intakes
 - 1.6 exhausts
 - Comp-cam 995-16
 - Valve springs 1.70" installed height, 130lbs at the seat
 - Comp cams 740-16 10 degree retainers & 10 degree valve locks
 - Crane roller rockers 1.5 ratio
 - Offset intake rockers, straight exhaust rockers
 - 450hp 340 Steel Crank
 - Penned rods
 - intake and headers all port matched
 - High volume sump and oil pump.

Camshaft:

Comp cams 20-224-4 extreme energy, 110 degree lobe centers, .488" intake valve lift, .491" exhaust valve lift, 230 degree duration @ .50" intake, 236 degree duration @ .50" exhaust. RPM operation range 1800-6000rpm. Comp cams custom length pushrods, comp cams hydraulic lifters. jr double row steel timing gear set. Estimated to be in excess of 370hp.

Carb: 900cfm Demon
Transmission: Keisler TK0-600 (0.82) 5-Speed Manual




Thanks for any help guys,
NZ

[Oldschool]

I think the 2.5" exhaust would perform better on a small block.  I haven't seen many small blocks that NEED a 3" exhaust.  Power adder motors might be able to utilize 3" exhaust on full throttle passes, but I wouldn't think an N/A motor would need 3".  I'm not sure 2.5" isn't more than you need.  My 0.02.......        

[Chryco Psycho]

the 2 types of headers are totally different
 the small tube step headers use stock bolt pattern / econo W2 heads
the large tube headers use the new/ race W2 pattern
 I just Emailed Sam a pic of the exhaust side of the head & he confirmed that my customer needed the large tube header to fit his application
 Personally I think you cam is too mild to warrant going to 3" exhaust  , dynoing the car with the exhaust in place & opening the cut outs on a separate pull wil tell you how much power if any you are losing to restriction

[Carlwalski]

Thanks guys, I'll go with the 2-1/2" exhaust and email my heads to someone.

The engine in the car is far from wild, I'm just wanting to squirt more hp out of it with the exhaust, but, if I do get a stroker motor for this car (416ci - 480-500hp) later on down the track would a 2-1/2" exhaust system handle that pressure or would I have to buy a 3" exhaust later on down the road? Thanks.

[Chryco Psycho]

even at 400 + ci I still feel the 2.5" will be adequate , why not ask Sam at TTi he may have some dyno data on his systems

[Oldschool]

      

[Carlwalski]

Thanks.

Obviously (like most members) I have no idea who "Sam" is but will email tti and attention it to Sam.

[KellysCuda aircard]

Thanks.

Obviously (like most members) I have no idea who "Sam" is but will email tti and attention it to Sam.

LOL..I dont know Sam either.. but there is a formula and I think flowmaster has it and for a certain amount of horsepower you need a specific size, to go the extra 1/2 inch in exhaust now will save you doing it later.

[Chryco Psycho]

Sam Owns TTi

[KellysCuda aircard]

Ahh, well then, Sam allready has some of my money...LOL

[moper]

If you want to go stroker eventually, buy the bigger pipe. You dont need it. It will just make it more obnoxious (some like me like that...lol), but it's the best choice for the later scenario. I'm assuming the same holds true for that huge carb you got there...WAY too big for the rest of the combo...

[Carlwalski]

I'll doubled checked to see what my carb was as I thought I was wrong when I posted.
It's actually a 650cfm Mighty Demon (my bad). I'll just stick with the 2-1/2" I think. The 440ci has the same.

[AprilsPink72Cuda]

I used the 2 1/2 in. on my 340 Cuda and I used the step headers.  No need for 3''.  I sure do love TTI's stuff!  I did go with the Flowmaster 40's over the dynomax mufflers though.   (Sam got my money too, but well well worth IMO).  I did notice an obvious increase in HP.

[Carlwalski]

I used the 2 1/2 in. on my 340 Cuda and I used the step headers.  No need for 3''.  I sure do love TTI's stuff!  I did go with the Flowmaster 40's over the dynomax mufflers though.   (Sam got my money too, but well well worth IMO).  I did notice an obvious increase in HP.

Thanks April. Did the Flowmaster mufflers need to be modified to fit with the tti exhuast?
I was thinking about getting a real aggressive growl from some Flowmasters.


Thanks,
Carlito

[AprilsPink72Cuda]

sorry I missed thius post NZ.  The mufflers didn't have to be modified but I had to cut the exhaust pipes.  The 50's I got first didn't work out because the floorpans got in the way.  Go with the 40's if you get Flowmasters o the Cuda.  The 50's fit perfect on Challengers though.