m8 head upgrade
Thread Starter
|
3rd Gear
Joined: Oct 2023
Posts: 7
Likes: 0
From: Fairbanks, AK
m8 head upgrade
I have a '23 RGS 114, currently in the process upgrading my bike. So far, I have upgraded to a WM8-22XD cam, SE cam plate and oil pump, HPI 62mm throttle body and intake manifold, FM 6.1 injectors, Thundermax ECU, SPC 2-1 exhaust, and I had the SE elite heavy breather but going to the HPI V2 (I didn't like how far the ram intake sticks out) engine work wise. My question is, I have done a good amount of research, and it seems like almost no body upgrades heads before going to a big bore kit/increasing displacement and I don't understand why. Even a stock head that can get ported and polished would increase flow and in theory would then increase your power. More air, more fuel, more power. Anyone have any insight into this? I am sure there is a point where more power means you are ultimately going to need to increase displacement, but I'm trying to get everything I can out of my 114.
Grand HDF Member
Joined: Aug 2020
Posts: 4,798
Likes: 5,889
From: Knoxville
I have a '23 RGS 114, currently in the process upgrading my bike. So far, I have upgraded to a WM8-22XD cam, SE cam plate and oil pump, HPI 62mm throttle body and intake manifold, FM 6.1 injectors, Thundermax ECU, SPC 2-1 exhaust, and I had the SE elite heavy breather but going to the HPI V2 (I didn't like how far the ram intake sticks out) engine work wise. My question is, I have done a good amount of research, and it seems like almost no body upgrades heads before going to a big bore kit/increasing displacement and I don't understand why. Even a stock head that can get ported and polished would increase flow and in theory would then increase your power. More air, more fuel, more power. Anyone have any insight into this? I am sure there is a point where more power means you are ultimately going to need to increase displacement, but I'm trying to get everything I can out of my 114.
Thread Starter
|
3rd Gear
Joined: Oct 2023
Posts: 7
Likes: 0
From: Fairbanks, AK
Understandable. I wasn't sure if it was because people just not being aware, or it's keeping up with the jones' or what. Or if it wasn't worth spending money on heads then upgrading later to a bigger displacement with again upgraded heads. I don't see myself upgrading to a bigger displacement any time soon so I'd like to get the most out of this current engine for as long as I can, and upgrading the heads seems essential to me. Thanks for the input.
Grand HDF Member
Joined: Aug 2020
Posts: 4,798
Likes: 5,889
From: Knoxville
Understandable. I wasn't sure if it was because people just not being aware, or it's keeping up with the jones' or what. Or if it wasn't worth spending money on heads then upgrading later to a bigger displacement with again upgraded heads. I don't see myself upgrading to a bigger displacement any time soon so I'd like to get the most out of this current engine for as long as I can, and upgrading the heads seems essential to me. Thanks for the input.
am far from an expert but know enough that installation of a cam without at a minimum porting and polishing the heads is as they love to say around here, leaving HP on the table. I wouldnt install a cam without matching the heads to the new flow as you know. Good luck in whatever you do decide.
Thread Starter
|
3rd Gear
Joined: Oct 2023
Posts: 7
Likes: 0
From: Fairbanks, AK
I am newer to the Harley engine building, but I went to school 13 years ago for automotive and have built plenty of engines since then, so I'm just using that information and knowledge towards this. I have already ordered all my parts, regardless it's what I'm going to do. I just thought it would have been more popular and I couldn't find much information on it unless it was pertaining to a bigger displacement build. But I appreciate it either way.
Road Captain
Joined: Jul 2020
Posts: 592
Likes: 481
From: SE PA
The stock heads have proven to support ~140hp. The heads aren’t a constraint on a 114. Big bore kit simply offers a much better bang for the buck.
Trending Topics
Road Master
Joined: Jun 2019
Posts: 952
Likes: 528
From: Richmond TX
The stock M8 heads flow substantially more than the twin cams. It may be that even with opening up the intake and exhaust plus a cam the heads are still not a limiting factor. Could be a negligible improvement until you start adding cubes.... Just an opinion.
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
Seasoned HDF Member
Joined: Feb 2009
Posts: 5,642
Likes: 1,985
From: Cleveland Zoo
A good running Stage II is easy to build and not expensive unless you buy not needed extras. A nice running Stage II also means you don't remove the heads, a lot of people here can do this at home. If you remove the heads, it's time to go big bore.
Grand HDF Member
Joined: Jul 2007
Posts: 3,740
Likes: 8,535
From: Bates County MO
Probably because stock heads have been shown to support up to ~150 TQ & ~145 HP on big bore kits. Hard to justify "bang for the buck" on a 114, considering it adds $2k to the price of a stage 2 setup.
