I was looking at getting my manifolds extrude honed to improve flow. Any feedback from you guys on the amount of benefit from this process? The Greddy manifolds are quite rough inside because they are cast iron.

 

I'm sure the benefit is measurable, but I would be surprised if it was significant. Since the air is being forced through the piping, surface roughness isn't as big as an issue as it would be for an NA engine where you benefit from scavenging and smooth, laminar airflow.

I doubt it's worth the cost, but it's an interesting thing to consider.

 

If you go that route, you might want to consider ceramic coating as well...to keep the manifolds from rusting. I was thinking of doing that prior to my install, but I ran out of time.

 

Manifolds and downpipes are already at the shop getting ceramic coating as we speak. Front and rear timing cover and intake plenum are all there as well for chrome powder coat. She should be puurty when I get the motor back together.

 

Oooh....very nice. I am happy that Greddy used the cast manifolds, sine they aren't prone to cracking like the mandrel bent steel manifolds. But they look damn ugly unless you coat them. )