Is compression release mandatory for 107 build?
Don't forget that the compression ratio is just that, a ratio. It represents the ratio between your combustion chamber's largest volume to it's smallest volume. As a result, a 10:1 ratio in a 88" motor requires less force than 10:1 in a 107" motor. In other words, as displacement increases, assuming the same ratio, the force required to compress the gasses increases. Unless your starter-motor torque increases porportionally with the displacement, it will work harder to crank the motor.
Simplifying the equation to compression ratio vs cranking power alone doesn't work.
Is it required? Probably not. Will the added displacement increase resistance on your starter? Yes.
A compression release alleviates a great deal of the required cranking torque.
Simplifying the equation to compression ratio vs cranking power alone doesn't work.
Is it required? Probably not. Will the added displacement increase resistance on your starter? Yes.
A compression release alleviates a great deal of the required cranking torque.
Thread Starter
|
Extreme HDF Member
Joined: Sep 2006
Posts: 10,114
Likes: 29
From: Vancouver B.C. Canada
Thanks for all your inputs!
FM charges an additional $100 for compression release installed which is a great deal.
I live too far away from FM, shipping those heads alone costs me $100 at least. I found a local Harley shop charges $200 for the pair ACR, really expensive. They charge $1400 for a pair of head porting and bigger valves, ridiculous! Wish I live in states, much better deal and quality work.
FM charges an additional $100 for compression release installed which is a great deal.
I live too far away from FM, shipping those heads alone costs me $100 at least. I found a local Harley shop charges $200 for the pair ACR, really expensive. They charge $1400 for a pair of head porting and bigger valves, ridiculous! Wish I live in states, much better deal and quality work.
Seasoned HDF Member
Joined: Mar 2007
Posts: 66,948
Likes: 4,573
From: TOAK western branch
Thanks for all your inputs!
FM charges an additional $100 for compression release installed which is a great deal.
I live too far away from FM, shipping those heads alone costs me $100 at least. I found a local Harley shop charges $200 for the pair ACR, really expensive. They charge $1400 for a pair of head porting and bigger valves, ridiculous! Wish I live in states, much better deal and quality work.
FM charges an additional $100 for compression release installed which is a great deal.
I live too far away from FM, shipping those heads alone costs me $100 at least. I found a local Harley shop charges $200 for the pair ACR, really expensive. They charge $1400 for a pair of head porting and bigger valves, ridiculous! Wish I live in states, much better deal and quality work.
Thread Starter
|
Extreme HDF Member
Joined: Sep 2006
Posts: 10,114
Likes: 29
From: Vancouver B.C. Canada
I am wrong! Just called them, $200 is for manual release, the auto compression release is $165 per head plus parts. WTF!!!!!!!!
Seasoned HDF Member
Joined: Mar 2007
Posts: 66,948
Likes: 4,573
From: TOAK western branch
ACR's themselves are much more espensive and you have to wire them into the harnes. For that price you could just buy the jig and sell it when your done. I think the jig is like 250.
Devil's Advocate
Joined: Jun 2010
Posts: 2,070
Likes: 36
From: Alberta, Canada
It would be cheaper to buy the tool and do it yourself.
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
Cruiser
Joined: Jun 2012
Posts: 145
Likes: 0
From: Maine
Better to have them then need them. What is your cold cranking pressure right now? Go to Big Boyz's website and put in your build info in the twin cam calculator this will give you a general idea. If you end up with 190 or higher I'd go with releases but my first statement is also true too. Hope this helps