I've been curious for a while about extrude honing. I understand it is pretty expensive(roughly over $300 for a IM to get worked), but the benefits are supposed to be pretty nice.

Now the questions:

When replacing or upgrading IMs, would a Extrude Honed p30 manifold make more power than a stock ITR IM? Thinking of Ericks ported GSR IM is what got me asking this questoin. I understand Ericks motor doesnt have an Extrude Honed manifold, rather a ported one. But just trying to make sense of this. I like the idea of cleaning up my stock manifold quite a bit, to make more top end, while keeping the longer runners to make a little better midrange.

When Extrude honing, is the amount of material removed from the inside a good amount, just a little bit, or however much you want removed?

If you have experience with extrude honing ANYTHING, please chime in.

 

I would like to know also.

 

here is a good thread
https://honda-tech.com/zerothread?id=104161
some one posted there before and after dyno plots but i cant find them. I think it might have been topspeed.

I did mine when I built the motor so I can't say if it helped one way or the other. I am using an ITR IM. I would like to do my head if I ever get into building another motor.
It smooths out the walls allot. There are a few threads on theoldone about the runners being top smooth.