I remember when extrude honing was promoted as the next big thing... at the time it was on the 5.0 Ford EFI intake manifolds...

Anyone on this forum ever extrude hone a set of e body hemi exhaust manifolds ? Does it really make any measurable difference in performance with a full length exhaust system?

Thanks
Craig

Measure the size of the ports on the heads and manifolds and then decide

Oh yes, extrude honing! I was one of those Foxbody Mustang guys. "Tmoss" was the guy people would send their intakes too for this procedure. I'm sure there would be measurable difference in flow on a set of exhaust manifolds and I'd be shocked if this wasn't already common place amongst the FAST (Factory Appearing Stock Tire) race class guys.

Several of the guys in F.A.S.T. say it's a waste of money.

I have pumped millions of tons of rocks of all sizes, plus very fine magnetite iron ore.

I have toyed with the idea of plumbing some cast iron exhaust manifolds into either
magnetic separator discharge pipes,
or froth flotation tailing discharge pipes
to see how long it would take to “round out” the exhaust manifold interior edges and passages.

Seems a shame to pay high Extrude Hone prices when hundreds of mineral processing plants “have to” have abrasives flowing through pipes.

A few days ago I visited a site where a very small coal cleaning “package plant” was being erected. The young foreman told me he had never before worked in mining but had spent years building drag racing engines professionally. He was doing this job because his grandfather needed him. The grandfather drove up awhile later and it turned out his 1960s entry into the coal business was pumping sand out of a riverbed and separating coal from the sand before selling the sand for construction projects.

We both knew Harry Ranier of NASCAR and swapped stories of his risk taking and “salesmanship” both on and off track.

https://en.wikipedia.org/wiki/Ranier_Racing_with_MDM

when my son was in engineering school, he was part of the SAE team. They built a motorcycle engine powered formula V type car and then took it to Detroit to be judged in a competition. I let the team use my flow bench as the school did not have one. We flowed the head and then they had it extrude honed, it looked pretty but flowed worse. Kind of like a river washing the wrong bank during a flood. It screwed the short side radius. The competition was about the engineering of the vehicle, not really how fast it went so it still did well in the competition. My only experience with extrude honing.

https://www.sae.org/attend/student-events/about-formula

We have built several stock resto type engines for customers that we extrude honed the intakes and exhaust manifolds. No before and after dyno comparisons, but they all made good power when done. Problem is the extrude hone process costs more that the actual manifolds do. Yes, it is pricey. For those looking for every h.p. but stoll looking factory such as the F.A.S.T guys the money is probably worth it.

Can't the F.A.S.T guys just do regular porting/grinding work?

discussed previously

old thead

Yes they can , Dave Dudek hand ported a set of Hemi exhaust manifolds , the honing pretty much polished the inside of the manifold form the pictures he posted on line ,I don't remember how much he said he gained , but it's wasn't a lot.

I think the gain is in smother airflow , it's not something that I think one would want to do in a WET intake manifold?

Thank you.... I tried the search function before posting but did not find this thread. Sorry. Craig

The “supersonic blow down” event in an exhaust manifold
is so different than
the “liquid with suspended solids” flow of Exude Hone
that your result is certainly believable.

On Larry Widmer’s old Honda message board my fuzzy memory is that he once wrote
“I have had good results porting exhaust manifolds, but when I quote the price no one want’s to pay”

Widmer and his aero engineer father certainly understood supersonic flow better than most.

I did back to back dyno testing on exhaust manifolds on my FAST 484 in Hemi. This was over 20 years ago so I don't remember the exact numbers but it only picked up very minimal horsepower. Somewhere in the five to eight horsepower range.

5-8 here, 5-8 there all make a difference in the long run.

Good air versus bad air on the same day at the track can have 30+ HP differences

True.

As is always the case……. YMMV.

I know someone who chassis dynoed a set of ex manifolds…… stock vs extrude honed….. back to back.
His words were…… no difference.

Though no expert. If a flow path is to be optimized over the original size and shape? Some areas need material removed, And very possibly some areas may need material added. Extrude hone can’t do that. For sure there are gains to be made with both intake and exhaust manifolds. But in my mind the science would be similar to porting an intake or exhaust port in a head.
Doug

It would be like bolting a head down on a cnc machine and hitting the start button without a program telling it what to do. lol