I am putting together a 350ci 5500 rpm engine similar to the humble pie by power and performance magazine. it was rated at just under 380 horsepower with headman headers 1 5/8" into a true dual exhaust 2 1/2 inch. my question is this how much power am i realistically going to kill off runing the headers into the headman 2 1/2" y-pipe and 2 1/2" single exhaust into a flowmaster 80 series with 2 2/1/2 outlets? I know that i will need more exhaust for maximum performance, but i can bolt all this back up and use it for a while untill i save up for the custom exhaust.
the part #s of my parts are y-pipe 17470. headers 68476

thank you..ryan

 

surely someone had dynoed such numbers somewhere?
does anybody know?

 

Can you bolt it back up? Sure.... How much power you will kill is unknown, but it will be significant compared to a 3.5 or 4 inch setup. So you know, even a 3 inch unit (common replacement) is smaller than the 2.5 dual.

 

scroll down a page or so and see a thread entitled "exhaust pipe diameter vs horsepower". Think that will clear things up for you.

 

i have already read that and according to that i will kill off over 100hp. my co workers that drag race laughed when i told them that. i see realistically a 20hp loss at the greatest. i was really looking to be pointed in the direction of someone who has dynoed both in comparison....thanks

 

More than 20 Hp, a lot less then 100HP. Since nobody even knows what YOUR engine will produce, we would have NO basis for estimating anything accurately.

It's like asking you how many apples are in the basket without telling you the size of the basket. Sure, we can see what the magazines engine made, but yours will not be the same.

 

my engine is pointless to the question. I am building using the same components as stated and if it doesnt make the same power who cares. 380ish hp with duals converted to a single 2 1/2 out of a headman y-pipe does what? I understand the statement and respect it but i need to know if theroetically my engine makes the same as the one above and does using duals as the above engine what will i loose with the single 2 1/2. I am a beginner but am learning. I have been around performace jap motorcycles for 15 years and am very familiar with them. v8 engines are very different. anyway, I just dont want to run out and customize my car with duals cutting or notching the crap out of the frame and whatever else neccessary unless absolutely needed. thanks alot guys...Ryan