Road Glide pinging
Outstanding HDF Member
Joined: Jul 2007
Posts: 3,410
Likes: 8
From: Knoxville, TN
10.5:1
This is what the heads were decked for using a stock thickness head gasket.
I installed a .030 Cometic.
I tend to think my compression may be around 10.8:1...but I don't know how to calculate for certain.
So I go with the specs Branch sent me, 10.5:1
This is what the heads were decked for using a stock thickness head gasket.
I installed a .030 Cometic.
I tend to think my compression may be around 10.8:1...but I don't know how to calculate for certain.
So I go with the specs Branch sent me, 10.5:1
Thread Starter
|
Road Warrior
Joined: Aug 2008
Posts: 1,318
Likes: 26
Thats a nice build!! Did you have pinging with the 585's. I thought the 570's were for lower compression motors, thats why I went with the 585. I think your right.....I went with the wrong cam. Damn it anyway.
Outstanding HDF Member
Joined: Jul 2007
Posts: 3,410
Likes: 8
From: Knoxville, TN
Let me get you some feedback on these 570's.
A couple buddies are wanting to find out about the 570's, too.
They're running 585's.
I get to be the guinea pig.
The 570's I believe are for a lower compression, however..this is the cam Branch recommended with their setup.
Being the "manly man" I thought I should be, I wanted it all.
Guess I'll return to my chic roots, drop a cam size...and ride off into the sunset.
LOL
Stellar HDF Member
Joined: Aug 2007
Posts: 3,159
Likes: 1,069
From: Brandon, Mississippi
The difference in loss in power from 9:5 to 10.5 is not allot of power left on the table period. Maybe 5HP if you have fuel that will not pre-detonate. The problem with high compression and pump gas you end up tuning the performance out of it so it will not detonate by pulling timing, or running it way fatter which is not efficient. At the end of the day you are no better off with higher compression over 10:1 in most cases. Personally, I do not know why so many choose to run the envelope of detonation on pump gas. On compression it is a linear curve. To get a decent gain in power from 9:5 you would need to go 12:5 for a meaningful power gain. Also remember these are obviously air cooled engines that run hot. That makes this engine more sensitive to detonation.
That all said, more is not always better. In the case of running a bottom end cam with shorter duration the static compression is going to be higher then it would be with a midrange cam. Low RPM detonation will rear its ugly head sooner, then a cam with longer overlap event.
All said and done I am not slamming anyone. I just think there is a huge misunderstanding about compression, versus power made, versus potential detonation issues as being discussed here. 10:1 on today's pump gas, is the edge with aluminum heads.
Just one mans opinion, who has built lots of performace oriented engines.
That all said, more is not always better. In the case of running a bottom end cam with shorter duration the static compression is going to be higher then it would be with a midrange cam. Low RPM detonation will rear its ugly head sooner, then a cam with longer overlap event.
All said and done I am not slamming anyone. I just think there is a huge misunderstanding about compression, versus power made, versus potential detonation issues as being discussed here. 10:1 on today's pump gas, is the edge with aluminum heads.
Just one mans opinion, who has built lots of performace oriented engines.
Thread Starter
|
Road Warrior
Joined: Aug 2008
Posts: 1,318
Likes: 26
The difference in loss in power from 9:5 to 10.5 is not allot of power left on the table period. Maybe 5HP if you have fuel that will not pre-detonate. The problem with high compression and pump gas you end up tuning the performance out of it so it will not detonate by pulling timing, or running it way fatter which is not efficient. At the end of the day you are no better off with higher compression over 10:1 in most cases. Personally, I do not know why so many choose to run the envelope of detonation on pump gas. On compression it is a linear curve. To get a decent gain in power from 9:5 you would need to go 12:5 for a meaningful power gain. Also remember these are obviously air cooled engines that run hot. That makes this engine more sensitive to detonation.
That all said, more is not always better. In the case of running a bottom end cam with shorter duration the static compression is going to be higher then it would be with a midrange cam. Low RPM detonation will rear its ugly head sooner, then a cam with longer overlap event.
All said and done I am not slamming anyone. I just think there is a huge misunderstanding about compression, versus power made, versus potential detonation issues as being discussed here. 10:1 on today's pump gas, is the edge with aluminum heads.
Just one mans opinion, who has built lots of performace oriented engines.
That all said, more is not always better. In the case of running a bottom end cam with shorter duration the static compression is going to be higher then it would be with a midrange cam. Low RPM detonation will rear its ugly head sooner, then a cam with longer overlap event.
All said and done I am not slamming anyone. I just think there is a huge misunderstanding about compression, versus power made, versus potential detonation issues as being discussed here. 10:1 on today's pump gas, is the edge with aluminum heads.
Just one mans opinion, who has built lots of performace oriented engines.
Stellar HDF Member
Joined: Aug 2007
Posts: 3,159
Likes: 1,069
From: Brandon, Mississippi
Yes I would give that a try. In the next breath, I will also say that while it fixes one problem, it screws up the squish a wee bit in the chamber, so you are again faced with a negligible loss in power. That said, ideally it should have been set up 10:1 on a zero deck. That not being a cheap option at this point, then yes I would increase the head gasket and drop the compression, Detonation if left unchecked will do one of two things or both. Hammer the rod bearings down to the copper, and in the worst scenario break a piston ring land. My highest recommendation is to solve this problem and quickly! >
Outstanding HDF Member
Joined: Mar 2005
Posts: 2,007
Likes: 4
From: Vancouver, B.C.
....
I'll throw in that you might get out the laptop and take some timing out at various throttle positions below, and up to 3000 rpm on both cylinders.
Try the link below to see a basic 'don't get yourself in trouble' timing table for a PC III from the Headquarters website. There is one for a SERT, etc.
CN
http://www.head-quarters-usa.com/efituning.pdf
Try the link below to see a basic 'don't get yourself in trouble' timing table for a PC III from the Headquarters website. There is one for a SERT, etc.
CN
http://www.head-quarters-usa.com/efituning.pdf
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
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
Southpaw Super Glide: A Left-Hand-Drive 1979 Harley FXE Built to Fit the Rider
Verdad Gallardo
The Best and Worst Harley-Davidson Moves of 2025
Verdad Gallardo
Thread
Thread Starter
Forum
Replies
Last Post
