only993

is this process worth spending the money on. I am about to get my valve guides done in my heads and was thinking about getting them extrude honed while they were apart, any noticable gains from this?

Anyone ever have this done?

bobesser

A little write up I did on extrude honing on another forum. Not sure if understanding the process will help your decision or not, but, I hope it helps.

This will take a moment and I do have a point so please read it all. Remember when you played with silly putty? Remember that if you grabbed it with both hands and pulled slowly it would stretch but if you pulled quickly it would snap apart? Remember you could bounce it like a ball but it would also flow out flat if you left it alone long enough? Silly putty is a non-newtonian fluid which is a fancy way of saying that it gets harder the harder you push or pull on it. If you throw it down it bounces if you set it down it flows like wet playdough. You can also have fun with non-newtonian fluids using corn starch and just enough water to get it all moist. YOu can't bounce it like a ball but if you punch it, it will resist your fist and if you lay your hand on it softly it will sink in like water.

Now back to the Extrude Hone. The material they use (they call it media) is essentially silly putty with some grit in it. When they push it through your manifold, it gets harder when there is a restriction to flow. When it gets harder it abrades the area. The harder it gets, the more it abrades. So, the more restrictive areas get more material removed from them and the less restrictive areas get less material removed.

If you had unlimited money, you would want to send your intake manifold, head, and exhaust manifold to them as a unit. Then you would get match ported and polished at both ends and really flow air.

Bob (Ph.D. Materials Engineer)

Amfab

thanks for that explanation

Marlon

So is it silly to putty the manifold or not???

Jim W

"silly to putty..."
That is funny!

TheOtherEric

I've heard from one person who has done this that you can get substantial hp gains by porting & polishing. It's not commonly done AFAIK so I'm reluctant to make any generalizations.

Jeff96-993

Just a couple of thoughts...

Extrude hone process typically is very hard on surface transitions. Through a long manifold it would work great smoothing out discrepancies in the surface. At the lead-in and exit though it would take a bigger bite. You might end up with something undesireable at those locations.

I'd think you'd want to keep it away from the valve seats, so I'd ask how they manage that.

Also, there are many different viscosities of media available. Everything from pudding to darn near hockey puck consistency. Pressures required vary considerably. Make sure you know what they're using, and that it's compatible with an aluminum manifold.

Mark in Baltimore

Great info. I've always been curious about the process.

matt777

Is there gains to be had by porting and polishing on these engines? If so, that will require a little more know how.

chris walrod

I feel the ceramic liners in the exhaust ports limit us on what can be gained.