Extrude Honing?

Ernie
I had a manifold, runners et al "extrude honed" about 4 or 5 years ago. Process took a couple of weeks and cost several hundred $ for a single intake on a 4 cyl. At the time Ford were using the same process (it's basically an abrasive mud squeezed through the orifices that cleans and polishes the surface) on one of their "sporty coupes" (the tricked up Contour maybe) and claimed a notable power increase. SOTP indicated it worked well.

My gut is that it would work well on a 348 given the plenum design where you are trying to increase flow. By comparison, it would likely not be the choice for a carb'd 308 (short runners, more tumble) but perhaps James/Kermit/others can chime in.

Philip

 

I have heard of this process off and on for 25 years now. Earlier efforts on Small Block chevs didn't turn out too well, perhaps due to the technology at the time. As I recall we flow benched a set that had been done in that manner and it didn't come close to what a hand ported job could do. At the time the problem seemed to center around thew difficuly in having the "slurry" of abrasives cut in areas that would increase the flow, as well as improve combustion characteristics. The areas of metal removal are pretty much dictated by extensive flowbench developement, and dyno results, if you want a power band that is complimentary to the rest of the engine modifications. As to flow bench results, they are actually easier to "dummy" than Dyno runs are, provideing you don't mind "stretching" the truth (advertising, ya know). I would be curious myself as to what they are doing with this process these days. Keep us posted, and if ya can, post pics.
Kermit

 

Pros, EH can get at areas that are difficult to get at with grinding-like devices.

For the airflow pattern of the 348 manifolds; notice that the air has a straight path from the helmholtz resonator to the back sides of the intake valve. This means two things; a) you can get at every point of the manifold surface with a grinder should you so choose; b) there is little to gain by porting and polishing if the rest of the engine is not stepped up to the new airflow of the modified manifold (cams, pistons,...)

This airflow pattern is completely different from american V8s where the airflow has at least 4 turns from the back side of the throttle places to the back side of the valve.

You see, air does not like to turn corners, and when it turns corners, it looses its laminar flow. Consider a 90 degree turn with air running through it. The air that has to travel the far side of the bend goes a considerable distance farther than the air on the near side. Bernouli's effect indicates that the air traveling the longer distance will have lower presure and the one traveling the short distance higher pressure. Since air is quite happy to readjust its flow based on pressure differences, in the bend air from the near side will be pulled towards the far side, and the airflow out of the bend will have two vortexes left and right rotating in the opposite direction. Therefore, each and every bend in the path of air causes both resistance and turbulence; both of which are bad for performance.

The American V8 cannot be packaged small enough with massive air horns sticking out of its top (see Hilborn mechanical Fuel injection ala Can Am era). So to package the engine, the engineers bned the manifolds around and cram them into the bay between the banks. This is good for packaging and bad for power. Its no wonder that a bit of port cleanup does wonders on these engines, they are strangled by the port shapes.

Notice that Ferrari V8 engines are not so constrained because: a) dry sumps, b) small displacements, c) mid engine orrentation; all allow the engine to be packaged with straight airflow.

 

I toured Extrude Hone's headquarters in Pennsylvania about a year ago, and was thoroughly impressed.

Their automotive department is just a fraction of the business that they do. General Mills, for example, used the Extrude Hone process on their Cheerios extrusion machine in order to get a huge increase in the rate of Cheerios production. The smoother internals of the extruder actually made a big difference.

Other customers' parts were more serious. Extrude Hone (the company, not the process) is used by NASA to make, among other things, hugely complex, 10-inch rivets for the space shuttle.

I can't say enough about their high level of technological knowledge. They actually have three stereo lithography machines, which lay down metal 0.001" at a time, in order to make parts that would be otherwise impossible to cast or machine.

Even more impressive was the detailed care that they treated the auto parts. There was a line of parts, mostly intakes, that had clearly marked instructions and multiple quality control checks. So, even though the automotive department is a fraction of their business, they have good people paying close attention to it.

One more thing: there's no need to compare a porting job with the Extrude Hone process. You could hand grind an intake manifold, and then have it honed to remove every last burr and leave a mirror polished surface.

It sounds like I work for them, doesn't it? I don't, but I was REALLY impressed with their operation.

--Matt

 

So, to answer your question ernie, I would definitely have your intake plenum honed.

 

I had it done to my Porsche track car. Best I can tell, it made the difference that was advertised. It enlarges the passageways to a small extent as well.

 

I only know about the F355 intake system, and in the throttle body is a small little lip that diverts air away from the injector nozzle in order to gain a better spray pattern. I would suspect that EH would not recognize that this lip was serving a purpose and grind it away to deliterious effect.