Porting & Polishing Heads = More Power?
Thread Starter
|
Tourer
Joined: Jan 2010
Posts: 485
Likes: 2
From: Colorado
Porting & Polishing Heads = More Power?
I've heard that many riders have gone with a Stage 2 (Stage 1 + Cams), then decided they wanted more power, so they sprang for a Stage 3 (Ported & Polished Heads). Can somebody please elaborate on the details of this upgrade and how it equates to more power?
Club Member
Joined: Jul 2008
Posts: 112,202
Likes: 1,316
From: On a hill among the hills, PA
Advanced
Joined: Mar 2011
Posts: 67
Likes: 0
Headwork reduces the amount or resistance for air entering an engine and exhaust leaving it. They simply flow more air than stock. More air means more oxygen/stroke. More oxygen means more fuel can be added, more bang, more power.
Anything that allows more air and fuel to be introduced to the cylinder for the combustion cycle will add power. Your engine is a glorified air pump, it sucks air in the filter, mixes with fuel, burns, then forces it out the exhaust. Any modification that will increase this airflow will increase overall power.
High flow air filters and intakes take care of the "air in" part. After the filter it enters the head, flows past the intake valve opened by the cam, is mixed with fuel, compressed and burned, then exits through the exhaust valve opened by the cam, and finally out the exhaust.
Anything that allows more air and fuel to be introduced to the cylinder for the combustion cycle will add power. Your engine is a glorified air pump, it sucks air in the filter, mixes with fuel, burns, then forces it out the exhaust. Any modification that will increase this airflow will increase overall power.
High flow air filters and intakes take care of the "air in" part. After the filter it enters the head, flows past the intake valve opened by the cam, is mixed with fuel, compressed and burned, then exits through the exhaust valve opened by the cam, and finally out the exhaust.
Thread Starter
|
Tourer
Joined: Jan 2010
Posts: 485
Likes: 2
From: Colorado
Yeah.....I'm sorta just trying to figure out if its worth my while. I'm pretty much only into cruising, but additional passing power is always nice, both in street traffic and on the freeway. Especially when riding 2-up. But I'm thinking that upgrading my Stage 1 to a Stage 2 with some good cams will probably be enough for my needs.
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
How fast do you want to go?
How long do you want to do it?
How much do you want to spend?
You get to pick 2.
Reading up on headwork is interesting, what works for one motor or even application ( incl. laden weight, gearing etc.) may not work for another.
and head work ( as mentioned above) really needs to be thought out as part of a package with exhaust, cams etc.
It really is deeper into the science than many of us go.
One of the very interesting, counter-intuitive, discoveries has been that a rough wall on the intake tract will contribute to better flow than a smooth wall.
Mike
How long do you want to do it?
How much do you want to spend?
You get to pick 2.
Reading up on headwork is interesting, what works for one motor or even application ( incl. laden weight, gearing etc.) may not work for another.
and head work ( as mentioned above) really needs to be thought out as part of a package with exhaust, cams etc.
It really is deeper into the science than many of us go.
One of the very interesting, counter-intuitive, discoveries has been that a rough wall on the intake tract will contribute to better flow than a smooth wall.
Mike
Last edited by mkguitar; Jan 31, 2012 at 02:41 AM.
Trending Topics
Road Warrior
Joined: Nov 2008
Posts: 1,595
Likes: 8
From: Vancouver Island British Colombia Canada
A rough wall on an intake will aid in beating the fuel molecules into smaller molecules which gives a more rapid burn.
Porting is designed to open the passage and allow faster entrance of fuel /air/ mixture into the chamber.
If the tech doing the mill work is not educated in porting, you are not going to get the benefit of better flow. Gotta look around for a shop with an awesome rep & the work isn't cheap.
A good set of cams & the proper exhaust is going to give you a huge boost in performance!
Hatch.
Porting is designed to open the passage and allow faster entrance of fuel /air/ mixture into the chamber.
If the tech doing the mill work is not educated in porting, you are not going to get the benefit of better flow. Gotta look around for a shop with an awesome rep & the work isn't cheap.
A good set of cams & the proper exhaust is going to give you a huge boost in performance!
Hatch.
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Verdad Gallardo
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Outstanding HDF Member
Joined: Oct 2009
Posts: 2,488
Likes: 30
From: Maryland near DC
head work mostly only helps at higher rpms as at the lower rpms the engine already gets all the air it needs, so for cruising it does not help much, also you need to match the heads with a cam that "allows more air to enter at the higher rpms...since most normally ridden hd's don't spend alot of time in the high rpm range its mostly a waste of time...search around for cam profiles for engines with head work and you will see where the power is improved (mostly above the 3000-4000 rpm range)...
Seasoned HDF Member
Joined: Apr 2006
Posts: 10,675
Likes: 95
From: Billings,Mt.
Yep engine work can get costly,especially if you pay someone to do it.