Which Header Diameter for 3.4 10.5.1 Twin Plug
 

I'm hoping you guys on the Engine Forum will have some experience with this header diameter issue and save me dyno-dollars.

I had Aase Motors build a 3.4L, ported/polished, 10:5.1, JE's, GE-60 Cam, twin plug, with 46MM PMO's. The exhaust ports are larger than stock, 41mm I think he said.

Which header diameter would produce more HP with the larger exhaust ports...1 3/4" Euro George or Stainless 1 5/8" stepped to 1 3/4" Header? They feed to a Flowmaster Series 40 two in/two out.

The builder believes with the large exhaust ports the 1 3/4 will allow the engine to exhale better and produce more power. I was told by another reputable shop that the muffler will not evacuate the larger headers fast enough, and that the smaller 1 5/8" stepped will draw better producing more HP.

I appreciate the thoughts here.

I would choose the 1.75 headers if i was building that motor.

Thank you Aaron. I have one of your distributors ;)

I trust my motor builder. After hearing a conflicting opinion from someone claiming to have dyno experience with this, I thought I'd throw it out there for the Pelican experts to chime in.

Headers
 

I heard yesterday that George Narbel passed away
Mike Bruns

his wife said it was lung cancer....RIP George.

Sad news. Sorry to hear that. Provided a great resource to the Porsche community for a long time.

Wow, that's sad. I'd spoken to him a couple of times and enjoyed chatting. He's a legend who will be missed.