thoughts on how much i should mill
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Cruiser
Joined: Oct 2012
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From: Morgantown, wv
thoughts on how much i should mill
Hey guys, I decided to go with the ev46 cam an was gonna do sum head work. 5 angle valve job, porting, an since I'm gonna be running stock pistols for now I was gonna bump compression by milling the heads. I'm wanting to get close to a 9:5:1 ratio. Couple of buddies told me to go .50 with a .30 gasket. Would that be about right or whAt are your guys experience with this. It's my first Harley build so I'm kinda in the dark on this.
Club Member
Joined: Jun 2007
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From: Bedford UK
I get uneasy when reading questions like this! Are you having your head work done by a professional tuning shop? If so, ask for their advice, as they can set your head and ports up to suit your cam and pistons.
Road Captain
Joined: Sep 2012
Posts: 675
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From: Massachusetts
set your compression based on your cam...dont just shoot for an arbitrary number. I used BigBoyzCycles in Maine for my heads (they oughta be back wednesday 
)
i went with a woods w6. Wood's AND BBC both told me to get the most out of that cam, I'd want to be right around 10:1 CR. (my original plan was to mill the heads)....i ended up doing pistons instead ($300 for the wisecos and $150 to bore over and hone the jugs to match the pistons). Upside is, if I ever have a problem and NEED to mill the heads, I can without worrying about valve clearances.
you're gonna need to pull the jugs anyways to do new base gaskets, and depending on milage, you MIGHT need to hone / re-ring anyways.
who's doing your headwork?
)i went with a woods w6. Wood's AND BBC both told me to get the most out of that cam, I'd want to be right around 10:1 CR. (my original plan was to mill the heads)....i ended up doing pistons instead ($300 for the wisecos and $150 to bore over and hone the jugs to match the pistons). Upside is, if I ever have a problem and NEED to mill the heads, I can without worrying about valve clearances.
you're gonna need to pull the jugs anyways to do new base gaskets, and depending on milage, you MIGHT need to hone / re-ring anyways.
who's doing your headwork?
Road Captain
Joined: Sep 2012
Posts: 675
Likes: 32
From: Massachusetts
I found that with my cam I could only get ~ 9.1-9.2CR reliably just by milling the heads
http://www.bigboyzcycles.com/calculators.htm
use the calculator, put in your cam, your engine, etc etc, and see what it comes up with. it's handy to be able to use it to take care of that pesky math (I do construction....not math lol)
i threw your numbers in there quick, and decking 0.050", with a .030 head gasket, with an EV46 cam (assuming all else is stock)
static CR 9.2:1
corrected CR 8.4:1
cold cranking compression 170psi
once again, assuming now that your heads are 83cc (and that they're both the same volume). did your head guy CC your heads yet?
Last edited by Jasper86; Nov 10, 2012 at 07:40 PM.
Thread Starter
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Cruiser
Joined: Oct 2012
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From: Morgantown, wv
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Seasoned HDF Member
Joined: Aug 2008
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From: Ohio
Jasper has you in the right direction, the EV46 can live with 9.8-1 to 10.0-1. 9.5-1 will be SAFE but slightly soft down low but you have a light bike. Invest in a adjustable ignition and run the compression up to 10.0-1 with that cam and have some fun.
Jasper, hows that engine project going?
Jasper, hows that engine project going?
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Road Captain
Joined: Sep 2012
Posts: 675
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From: Massachusetts
we'll know more next week. Bean told me I should have the heads back by the middle of the week, then I can start reassembly. (the new progressive monotubes oughta be here wednesday too)
it's as far as I can take it at the moment, so I started mocking up the new bars. should be able to run some romex to figure out my cable lengths, hopefully order those on monday
it's as far as I can take it at the moment, so I started mocking up the new bars. should be able to run some romex to figure out my cable lengths, hopefully order those on monday
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Cruiser
Joined: Oct 2012
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From: Morgantown, wv
I did sum checking an asking around. Im going to end up sending my heads to big boys. Instead of the other guy I was gonna use. They are more known also alot of recommends to them. More experienced than the other guy an turns out to be way cheaper then the guy I knew. So I know they will be done correctly and a great job.