Exhaust header size for a 3.0?

[patssle]

What is the appropriate exhaust size for headers on a 3.0L carbed (and will be in a 914)? 1/2, 5/8, 3/4?

Thanks.

[Steve@Rennsport]

Good question,...

Header size selection is based on the engine's configuration. Variables such as cams, compression, intake system (carbs), all factor in the choice.

With SC or 964 cams, you'd do best with 1.5" ones. Remember too, its the rest of the exhaust system that makes the biggest difference since these engines are much more sensitive than people know.

[patssle]

Thanks! Any other opinions, or is the 1.5" agreed upon? If I go larger since the 1/2s aren't as widely available, does it create any issues...or just a little less power or something?

For muffler, I plan on taking the one it is currently using on the 911.

[patssle]

Bump!

[aston@ultrasw.c]

Originally Posted by patssle

Bump!

i'm not an expert but it sounds like you need a quick answer.

people who know have posted that a larger than recommended header dia will have a significant impact on low end performance. I would stick with the 1.5"

[175K911]

You'll be hard pressed to find better advice than that offered by Steve Weiner. Stick with 1-1/2"

[kent olsen]

Steve's right it's all dependent on the engine mods. My 81 3.0L has 40mm weber's, Dougherty GT2-102 cams, 9.5:1 pistons and European 1 1/2' headers, twin plug heads and make 245hp at the crank.

[patssle]

Thanks guys, will go with the 1.5". Nothing against Steve, I just like to have multiple opinions on big purchases!

[78SCRSMAN]

At what point would a 3.0 benefit from 1 5/8" tubes?
10.5:1 cr?
ITB's?
particular cams?

[Steve@Rennsport]

Originally Posted by 78SCRSMAN

At what point would a 3.0 benefit from 1 5/8" tubes?
particular cams?

Thats correct,...

[78SCRSMAN]

I'm guessing only the highest lift/longest duration variety cams that would create a high reving, manic type racing motor?

[patssle]

Ok, time to clarify. Were you guys talking 1.5" ID or OD? I was about to place the order, but the header guy (who's been making em for 30+ years) says I need 1/2" ID, thus 5/8ths OD.

[78SCRSMAN]

You will want to purchase the 1 1/2" ID headers.

[Evans, Marv]

+1 - 1 1/2 id.

[patssle]

Ok that's what I thought, just wanted to make sure. Thanks!