Compression increase, how much more hp and torque
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Novice
Joined: Jul 2009
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From: Littleton CO
Compression increase, how much more hp and torque
Okay I did a search and looked on 8 pages of posts and didn't see the answer.
I am trying to get horsepower/torque increases in my 88 ci 2006 street bob for as little money as I can (have a young family).
Currently I have a stage 1, with AN "big sucker", slip-ons, and AN fuel tuner.
I am looking at installing a Andrews 37h after which I want to mill the heads to get to about a CR of 9.5 or 9.8 at sea level. Badboyz want's 70$ to mill the heads (I'm thinking around .05" off = 9.5:1) and I can't see a cheaper way than that to get more oomph where I am currently at. 70$ is easy for me to come by, $200-$600-$2k for other mods is not.
So my question is:
What is your best guess as to the hp/tq gain with the above increase in Compression ratio from stock 8.9:1?
I do intend to install good 2-into-1s and port the heads in a few years.
I am a newby , thanks for any advice.
I am trying to get horsepower/torque increases in my 88 ci 2006 street bob for as little money as I can (have a young family).
Currently I have a stage 1, with AN "big sucker", slip-ons, and AN fuel tuner.
I am looking at installing a Andrews 37h after which I want to mill the heads to get to about a CR of 9.5 or 9.8 at sea level. Badboyz want's 70$ to mill the heads (I'm thinking around .05" off = 9.5:1) and I can't see a cheaper way than that to get more oomph where I am currently at. 70$ is easy for me to come by, $200-$600-$2k for other mods is not.
So my question is:
What is your best guess as to the hp/tq gain with the above increase in Compression ratio from stock 8.9:1?
I do intend to install good 2-into-1s and port the heads in a few years.
I am a newby , thanks for any advice.
Outstanding HDF Member
Joined: Oct 2007
Posts: 3,437
Likes: 15
save your money until you can port at the same time. Simpley decking your heads will not give you enough to make pulling your motor apart a second time. That being said you will pick up a little torq down low but hp will be about the same.
Cruiser
Joined: May 2007
Posts: 198
Likes: 0
From: Colorado Sprgs, CO
Okay I did a search and looked on 8 pages of posts and didn't see the answer.
I am trying to get horsepower/torque increases in my 88 ci 2006 street bob for as little money as I can (have a young family).
Currently I have a stage 1, with AN "big sucker", slip-ons, and AN fuel tuner.
I am looking at installing a Andrews 37h after which I want to mill the heads to get to about a CR of 9.5 or 9.8 at sea level. Badboyz want's 70$ to mill the heads (I'm thinking around .05" off = 9.5:1) and I can't see a cheaper way than that to get more oomph where I am currently at. 70$ is easy for me to come by, $200-$600-$2k for other mods is not.
So my question is:
What is your best guess as to the hp/tq gain with the above increase in Compression ratio from stock 8.9:1?
I do intend to install good 2-into-1s and port the heads in a few years.
I am a newby , thanks for any advice.
I am trying to get horsepower/torque increases in my 88 ci 2006 street bob for as little money as I can (have a young family).
Currently I have a stage 1, with AN "big sucker", slip-ons, and AN fuel tuner.
I am looking at installing a Andrews 37h after which I want to mill the heads to get to about a CR of 9.5 or 9.8 at sea level. Badboyz want's 70$ to mill the heads (I'm thinking around .05" off = 9.5:1) and I can't see a cheaper way than that to get more oomph where I am currently at. 70$ is easy for me to come by, $200-$600-$2k for other mods is not.
So my question is:
What is your best guess as to the hp/tq gain with the above increase in Compression ratio from stock 8.9:1?
I do intend to install good 2-into-1s and port the heads in a few years.
I am a newby , thanks for any advice.
If you are simply looking for more low end tq and a performance bump, cams should be looked at before headwork IMHO.
Thread Starter
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Novice
Joined: Jul 2009
Posts: 18
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From: Littleton CO
The cam's have been bought, not installed. After that, I'm not going to have money for quite a while to do anything else, that's where the heads question came in.
So, when I tear it down this winter, I will just wait on the heads like everyone is saying. It sounds like I'll probably be pretty happy with what I get with the cams.
Thanks for everyone's input.
So, when I tear it down this winter, I will just wait on the heads like everyone is saying. It sounds like I'll probably be pretty happy with what I get with the cams.
Thanks for everyone's input.
Road Warrior
Joined: Nov 2007
Posts: 1,984
Likes: 7
Many years ago, when I was young and the world seemed simpler, the general idea was that for every whole number of compression increase you got two(2) HP per cylinder.
All other things being the same.
But like what has been said it is a process. One thing needs or can use another.
You don't want high compression just to have high compression. That particular road will cost too much.
I would just put in a Woods 6 cam that works well and do other stuff later. The 0.510 lift one. Big time increase to the seat of the pants. Everything else stock. If you got to do something.
I know the young family thing. Enjoy all that.
All other things being the same.
But like what has been said it is a process. One thing needs or can use another.
You don't want high compression just to have high compression. That particular road will cost too much.
I would just put in a Woods 6 cam that works well and do other stuff later. The 0.510 lift one. Big time increase to the seat of the pants. Everything else stock. If you got to do something.
I know the young family thing. Enjoy all that.
Last edited by Old Gunny; Jul 25, 2009 at 05:36 PM.
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