87camaro kid

is there really any big diffrence between the 2 like performance or sound im usre there is but is it a big diffence? i just got hedman 1/5/8 headers with 3in collectors but the y pipe that it comes with is only 2.5 which sux

MdFormula350

hey at least you got headers which will still help over the stock manifolds and y-pipe. you should be fine with what u have.

a nice highflow cat or straight to go into ur flowmaster catback should work nicely.

overall not a bad exhaust system u put together.

87camaro kid

thanx yeah i thought it should be alright...im just ganna run with out a cat cause im geting rid of my air pump any way

92RSFivePointSlow

if your smallest restriction is 2.5" I would say there is no potential gain for you to run any pipe rearward of that which is bigger. BUT unless you're using an expensive 2.5" muffler, you will find it easier to maintain flow with a 3" muffler. It took me forever to figure out why people use 3" pipes, it's because the bigger muffler doesn't restrict as much as a 2.5" one, even though a straight 2.5" piece of pipe probably flows more than most 3" mufflers.
If my theory is correct, using your 2.5" y-pipe you'd get the same effects of a full 3" cat-back if you used 2.5" piping that adapted to a 3" muffler.
Someone will probably disprove me by pointing out the expansion chamber of a two-stroke motocrosser and why the shape of them make a difference.

383backinblack

to my knowledge expansion chambers will only work on a 2 stroke, but anyways

obviously a 3" exhaust will outflow a 2.5 inch system,

but if your motor doesnt need the extra flow, your not going to gain any power by using a bigger pipe

alfizzo

your only making 410hp with a 383 and afr 210 heads? i just did a few break in dyno pulls on my 383 with 200cc pro lighting heads and pulled 460hp. iam getting a set of afr 210 just to get to the 500hp mark. did you dyno test the engine? of is the 410 rwhp?

383backinblack

410HP at the rear wheels.....

and since it was dynoed i've picked up another 5mph in the 1/4.....so its more likely around 430-440 now

which would put it in the 550 region at the flywheel.....and something is still holding it back, im workin on it

pvt num 11

I'm thinking about doing Hooker Headers and dual 2.5" out to some Flowmasters, right now I have no engine or intake work at all, would I benefit later from having a 3" or is it not worth the extra money? (383 build in the next few years...)

jimmy_mac

The collector from the 2 2.25 inch pipes into the 2.5 inch pipe is right at about 3inchs. It is very easy to buy a 3inch 90 degree mandrel bend and a 45 degree bend to replace that 2.5 inch piece and they fit nicely over the cut y pipe collector.

Another option is to cut back to the 2.25 inch pipe and run dual mandrel 2.25 inch bends around the same route. That is what I have done and am dumping right before the axle. But you could also merge them into a 3inch pipe at any point.

I can tell you though from cutting into that Y pipe. That merge from the two 2.25 inch pipes into the 2.5 inch is pretty ugly. Those two pipe run straight into a wall. And the 2.5 inch pipe on mine at least stuck into the collector to far. Looked like a pretty bad disruption in flow.

And a single 2.5 inch pipe is got to be cutting it close to robbing power even on a mildly modded 305.

Parrydise7

iTrader: (1)

I added a 3" Y pipe from an IROC to my 85 LG4. I already had an Edelbrock cat back system. There was a modest gain in power (I just happened to put it on a dyno after that) and it did sound just a little bit better. As I recall, it added all of about 9 horses. Now, that is on a pathetic LG4. The hotter the engine, the greater the improvement. Somebody told me you can expect 20 to 30 horses from that modification alone.