Cam for low end tork
Grand HDF Member
Joined: Sep 2017
Posts: 4,359
Likes: 1,219
From: Dubuque, IA
it all about the having the compression set right for the cam.
Seasoned HDF Member
Joined: Mar 2010
Posts: 38,525
Likes: 6,406
From: Honah Lee
Higher lift cams require adjustable pushrods fill the cylinders more and usually have more overlap allowing more fuel/air mixture and time fire exhaust to escape.
Hurts bottom end and causes a coarse idle. Unless one is not satisfied with what a stock Harley does at WOT, leave it as is.
Raising compression, adding high lift cam along with increasing valve springs tension will require compression release for starting. Of course at upper RPM, you gain more power back. Of course it takes more fuel for that power. It's not free.
If someone had a bagger, two up and a trailer, they might consider a change to the drive ratio rather then the engine.
I know.
... Save someone the trouble. 
Last edited by Jackie Paper; Aug 10, 2023 at 05:54 AM.
Grand HDF Member
Joined: Sep 2017
Posts: 4,359
Likes: 1,219
From: Dubuque, IA
It does take an extreamly small amount of the engine power to turn a set of gear driven cams versus chain driven cams.
Higher lift cams require adjustable pushrods fill the cylinders more and usually have more overlap allowing more fuel/air mixture and time fire exhaust to escape.
Hurts bottom end and causes a coarse idle. Unless one is not satisfied with what a stock Harley does at WOT, leave it as is.
Raising compression, adding high lift cam along with increasing valve springs tension will require compression release for starting. Of course at upper RPM, you gain more power back. Of course it takes more fuel for that power. It's not free.
If someone had a bagger, two up and a trailer, they might consider a change to the drive ratio rather then the engine.
I know.... Save someone the trouble.
Higher lift cams require adjustable pushrods fill the cylinders more and usually have more overlap allowing more fuel/air mixture and time fire exhaust to escape.
Hurts bottom end and causes a coarse idle. Unless one is not satisfied with what a stock Harley does at WOT, leave it as is.
Raising compression, adding high lift cam along with increasing valve springs tension will require compression release for starting. Of course at upper RPM, you gain more power back. Of course it takes more fuel for that power. It's not free.
If someone had a bagger, two up and a trailer, they might consider a change to the drive ratio rather then the engine.
I know.
... Save someone the trouble. 
Stellar HDF Member
Joined: Aug 2020
Posts: 3,175
Likes: 2,221
From: College Station, TX
I don't see the bike listed or the specs on either cam. But generally, most cams that provide torque at lower RPM (when the cam comes on) typically close the intake valve earlier which increased the pressure in the cylinder. If you already have a big bore, high compression engine (11:1 or so) and install a torque cam, you could end up with some issues starting and pinging because of high cylinder pressure. With the specs for the current engine, you can calculate static compression etc.
The idea is that the cam works with the other engine components (pistons, heads, exhaust ans intake etc). Most cam suppliers will describe when the cam starts making torque and what engine it will work with (stock or highly modified). So if you have a specific cam selected and know the exact specs of you engine, that should give you a better understanding of how it will work with your current setup.
http://www.bigboyzheadporting.com/TwinCamComp.htm
Paul
The idea is that the cam works with the other engine components (pistons, heads, exhaust ans intake etc). Most cam suppliers will describe when the cam starts making torque and what engine it will work with (stock or highly modified). So if you have a specific cam selected and know the exact specs of you engine, that should give you a better understanding of how it will work with your current setup.
http://www.bigboyzheadporting.com/TwinCamComp.htm
Paul
Road Captain
Joined: Jul 2020
Posts: 592
Likes: 481
From: SE PA
Generally, torque based cams close the intake valve sooner than a mid-range focused cam or a top-end focused cam, etc. All else equal, a cam with an earlier closing point, say 20 degrees ABDC, will translate to greater cranking compression vs. one with say a 40 degree close ABDC. As such, it will take more energy to fire. This is even more noticeable with kick start bikes, where a cam with a later intake valve close makes the bike easier to kick through the compression stroke.
Seasoned HDF Member
Joined: Mar 2010
Posts: 38,525
Likes: 6,406
From: Honah Lee
Generally, torque based cams close the intake valve sooner than a mid-range focused cam or a top-end focused cam, etc. All else equal, a cam with an earlier closing point, say 20 degrees ABDC, will translate to greater cranking compression vs. one with say a 40 degree close ABDC. As such, it will take more energy to fire. This is even more noticeable with kick start bikes, where a cam with a later intake valve close makes the bike easier to kick through the compression stroke.
Trending Topics
Stellar HDF Member
Joined: Aug 2020
Posts: 3,175
Likes: 2,221
From: College Station, TX
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
Thread Starter
|
Road Warrior
Joined: Jun 2014
Posts: 1,556
Likes: 802
From: MN
Ok guys , your mechanical knowledge trumps my comprehension. My bike is a 2017 FATBOY with a stage one. Everything I had herd here was pos for a 2 upgrade until someone mentioned the harder cranking possibilities which is where we are now. I guess the bottom line is do I want to spend the money with the possibilities of having something go wrong.