Head porting and balancing
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HDF Community Team
Joined: Dec 2005
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From: NC USA
Head porting and balancing
I've done a LOT of research and talked to many about flywheel balancing and have formed my own opinion concerning that, but if anyone has had miraculous results, I'd listen...
Head porting - I've NOT done much research or talked to anyone who has had that done. So maybe I could hear from some of you who have, that ride their bike on the highway - rather than people who sit around talking dyno figures?
Head porting - I've NOT done much research or talked to anyone who has had that done. So maybe I could hear from some of you who have, that ride their bike on the highway - rather than people who sit around talking dyno figures?
Road Warrior
Joined: Jan 2007
Posts: 1,276
Likes: 8
From: Minneapolis Area, MN
I did way too much work at once to know exactly how much diff the light "street" port made on my '98 Wide Glide.
I put in a mild EV27 cam, bored cylinders .010" over, heads shaved .060", street port, 5 angle radius grind, Rinehart 2-1 ceramic coated pipe and a Mikuni HSR42 carb. Since I did this during the winter, it was tough for me to tell just how much stronger the bike is. The compression went from 132 to 185.
I had a friend ride it and he was amazed how much faster it felt than his Dyna which has the same cam and some aftermarked exhaust.
I raced an '07 Road King and smoked him...he was pissed.
I've never had my bike dyno'd...but I'd like to.
I put in a mild EV27 cam, bored cylinders .010" over, heads shaved .060", street port, 5 angle radius grind, Rinehart 2-1 ceramic coated pipe and a Mikuni HSR42 carb. Since I did this during the winter, it was tough for me to tell just how much stronger the bike is. The compression went from 132 to 185.
I had a friend ride it and he was amazed how much faster it felt than his Dyna which has the same cam and some aftermarked exhaust.
I raced an '07 Road King and smoked him...he was pissed.
I've never had my bike dyno'd...but I'd like to.
Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,897
From: Bedford UK
Head porting normally goes with other modifications and not on its own, so it is unlikely anyone has experience of the benefits of just doing that.
I had my evo stroked to 89 inches with a JIMS crank kit, higher comp pistons, Crane cam, ported and gas flowed original heads to suit the other improvements. Almost doubled horsepower, but made the bike much smoother and easier to ride.
So if you are thinking of going that route, I suggest you speak to an engine specialist and talk through what you want at the end of it all, which is what I did. I rode it in and a few days later rode it home - with a silly grin!
I had my evo stroked to 89 inches with a JIMS crank kit, higher comp pistons, Crane cam, ported and gas flowed original heads to suit the other improvements. Almost doubled horsepower, but made the bike much smoother and easier to ride.
So if you are thinking of going that route, I suggest you speak to an engine specialist and talk through what you want at the end of it all, which is what I did. I rode it in and a few days later rode it home - with a silly grin!
Extreme HDF Member
Joined: Nov 2006
Posts: 13,389
Likes: 26
From: Windham,Maine
Always have done all those things to my motors because,every little bit helps in the end.Most of the small things you do you will not feel seat of the pants but done right,it does all add up.Good Luck
Elite HDF Member
Joined: Sep 2007
Posts: 4,468
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From: Bluffton, South Carolina
An engine is nothing more than an air pump. That being said anything that will allow more air in and out will produce more power if properly tuned. On the subject of balancing, it will cut vibrations down all over and especially in a band of RPM's that it was balanced for. Felt vibrations are what you feel when the rotating parts of your engine are deviating from their canterline because of the imbalance of the affected parts. Simply stated the inside parts want to get outside. This causes extra load on bearings and cylinder, and extra side loads on rods and pistons. This extra loading increases friction and therefore equates to power loss. Additionally the harmonics can affect the ring seal and the protective lubricating layer of oil in the engine, again both of these cause power loss. These harmonics can cause early failure of parts jn an otherwise good engine.
This was a little wordy, but I hope this helps.
This was a little wordy, but I hope this helps.
Last edited by miacycles; Jan 11, 2009 at 09:32 AM. Reason: typo
Road Warrior
Joined: Apr 2007
Posts: 1,952
Likes: 15
From: Senoia, Ga., by way of Miami, Fl..
OK. I had NO intention of doing it to mine, just wanted some opinions.
I had a feeling it was not much advantage without a LOT of other mods. And I agree in theory - the more you can "move" the more it will do. However, when you're sucking in explosive mixture (gas/air) with the intention of making the "pump" do the work, rather than the pump being the result of another power source, that changes the formula. I've read a little, but enough to realize the angle and velocity of the mixture intake is a big factor pertaining to what's actually (supposed to be) happening.....
hmmmm ... maybe I forgot my medication this morning
I had a feeling it was not much advantage without a LOT of other mods. And I agree in theory - the more you can "move" the more it will do. However, when you're sucking in explosive mixture (gas/air) with the intention of making the "pump" do the work, rather than the pump being the result of another power source, that changes the formula. I've read a little, but enough to realize the angle and velocity of the mixture intake is a big factor pertaining to what's actually (supposed to be) happening.....
hmmmm ... maybe I forgot my medication this morning
Not totally related, but have you heard of the theory that HD rods are sometimes twisted? Causing side loading and premature ring and cylinder wear... ?... I read an interesting article once that went into prety good detail, advising that the rods may need to be "tweeked" whenever the engine is taken down to that point.. Just curious, didnt mean to sidetrack, but it would certainly pertain to balancing the rotating assembly..
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HDF Community Team
Joined: Dec 2005
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From: NC USA
Not totally related, but have you heard of the theory that HD rods are sometimes twisted? Causing side loading and premature ring and cylinder wear... ?... I read an interesting article once that went into prety good detail, advising that the rods may need to be "tweeked" whenever the engine is taken down to that point.. Just curious, didnt mean to sidetrack, but it would certainly pertain to balancing the rotating assembly..
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Club Member
Joined: Jun 2007
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From: Bedford UK
I have read mention in several places of "bent rods" with no further explaination... If a valve dropped and jammed up the works that would be a no-brainer, but the service manuals mention checking the rods for "bent" in routine engine re-building. Looking at the combustion chambers, there is about 20 - 30 percent of unused space, putting the firing force on the left side on the piston.... interesting.
Harley is not alone in using offset shaped combustion chambers. It does not result in the firing force on one side of the piston. The combustion space is like a balloon, with equal pressure all around and pressing across the whole piston surface at the same time. Think of sidevalve engines - they have an extreme form of offset, but have survived without rod problems caused by the offset.
Road Warrior
Joined: Apr 2007
Posts: 1,952
Likes: 15
From: Senoia, Ga., by way of Miami, Fl..
I have read mention in several places of "bent rods" with no further explaination... If a valve dropped and jammed up the works that would be a no-brainer, but the service manuals mention checking the rods for "bent" in routine engine re-building. Looking at the combustion chambers, there is about 20 - 30 percent of unused space, putting the firing force on the left side on the piston.... interesting.
Yea, not quite a "bent rod", thats more obvious. I'll see if I can find that article. Its more related to what grbrown mentioned. This article actually shower the tech twisting the rod into proper alignement. I'll start another thread if you'd prefer, I just thought it was related. Let me know..