hp question

[ice87]

I'm collecting parts to build a 350-400 HP 355 for my k5 and was wondering if a header with a 1.5 primary tube can make that goal or if I need to get a header with 1 5/8 primary tube

[xjs3667]

well   your going to need a lot more than headers to make that goal       jk

[ice87]

Well I know that that. Headers are the only thing left that I'm not sure which way to go.

[marshall]

Both are a little small, 1 3/4 I would suggest

[ice87]

Both are a little small, 1 3/4 I would suggest

what would you suggest?

[xjs3667]

I would go 1 5/8.....    I envy you if headers is all you got left..... Im just starting on my 355 build   guna be around 450-500hp range

[marshall]

Both are a little small, 1 3/4 I would suggest

what would you suggest?

1 3/4" headers

[Jthomas]

Headers matter a lot. And on a naturally aspirated motor, to achieve max power you need to achieve maximum volumetric efficiency. You do need a nice flowing motor and I'm sure that 1 5/8 - 1 3/4  would be ok for a small block. 

Talk to the proformance department at Chevrolet, they will tell you EXACTLY what it needs

Found this in my chevrolet performance manual.  This is what you need for a balls out small block. 

[xjs3667]

Headers matter a lot. And on a naturally aspirated motor, to achieve max power you need to achieve maximum volumetric efficiency. You do need a nice flowing motor and I'm sure that 1 5/8 - 1 3/4  would be ok for a small block.

Talk to the proformance department at Chevrolet, they will tell you EXACTLY what it needs

Found this in my chevrolet performance manual.  This is what you need for a balls out small block.

I believe this is refering to if you were to run open headers as on a race engine.... correct me if I am wrong




also we do need to know if you are running and exhaust or just gunna run open as it does make a difference

[Jthomas]

I'm not sure what they are calling a "tail pipe" but I'm assuming any exhaust after the header?

If not, well it gives you the length and size if ur going open header. This straight from CHEVEROLET PROFORMANCE.