Porting with Extrude Hone?

[Georges Fonso]

Hello all,

This is my first post in this Forum and, as such, first of all I'd like to greet everyone and thank GC for accepting my registration with the site.

I would like to have your views (and experiences, maybe?) regarding the Extrude Hone process when used in cylinder head porting applications.
From what i see and read, in the last five years it is getting somewhat popular on the other side of the Atlantic. I can see its merits when it comes to smoothing out an inlet manifold/ plenum etc, but I have my objections when it comes to porting, especially because of SSR considerations and the like. Also, what happens in cases when you don't want to fettle with one side (or even one plane) of the port at all? To me, it seems too easy to be as "miraculous"as it it being advertised...

I can think of some applications where it could surpass "traditional methods" (e.g. manifolds as above, transfer tracts in two-stroke cylinder barrels etc, in other words out of reach areas where geometry is not critical because of their function or of limited ground for geometrical improvement), but I am a bit sceptical about the method when it comes to head porting.

Perhaps it could be used as a good supplement to "traditional" porting (by hand or CNC)? In cases where you have made the shape and dimensions of the port the way you want them, and have just left the surface finish to go? Then again, compared to all the previous flowbench and machining work, how much time will it take to grit the ports? Is Extrude Hone worth its salt when it comes to its so very much advertised cylinder head applications?

I've heard that some makers of CNC ported heads (including rumors about Cosworth being one...) use Extrude Hone as the last stage of their porting, in order to give the work a "traditional" grit finish and, sometimes, in order for the job to look "hand made"...

So, what do you think?

G.F.

[superbike]

I have had a brief look at extrude hone and i gather all it can do is provide a good finish and enlarge the port as a whole which may not be ideal. It probably takes as long to set the machine up as it does to carefully polish your ports at 80 grit anyway.

Just my 1 cents worth!

[Georges Fonso]

Hello Superbike!
Thanks for looking.
More or less what I thought as well.
I am still very curious of any first-hand experience in this forum --If anything, for the sake of conversation...
I'd also like to see what our host thinks of the subject...
Best Regards, everyone!
G.F.

[Guy Croft]

What the host thinks? How courteous!

Sorry to 'kill it' dead, but those things, as Chris indicates, are for finishing when the port shape has already been determined ie: machined, fettled, or of course 'built-in' by design and casting.

They might well be able to remove a mass of metal if left running long enough but they are unable to do it selectively. Plus they are fantastically expensive.

GC

[Georges Fonso]

GC-

Smiling for your comment, I agree with you that it cannot do it selectively -- however the manufacturer claims otherwise.

Just for the record and summing up the manufacturers' claims, it is supposed to remove more material wherever the abrasive media finds an obstruction to its flow (fairly reasonable, I'd suggest...) and just "smoothen out" the free flowing areas.

Of course, a highly viscous plasticine - like abrasive material flows a whole lot differently than our beloved fuel mixture, so let's all praise the time-honored flowbench, grinder and gritter.

G.F.

[Guy Croft]

Removes metal where it finds an obstruction. Mmm..

I wonder what it would make of the splitter vane in a multivalve head?!

GC

[Georges Fonso]

I suppose something like that... You grinning or what?
Could that be the same port? Unless i need to visit my optician, the "Before" port has two valves and a splitter, the "After" a single bronze guide in place of the splitter. Maybe we' re witnessing a miracle, or the person who provided the webmaster with the above material doesn't know much about his/her job

G.F.

[Mats]

Two valves? Looks like a clean radius for the "fin" before the guide?

Won't there be a "boundry layer" of some sort in the extrude hone material?