question about compression ratio
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Tourer
Joined: Mar 2015
Posts: 301
Likes: 1
From: las vegas
question about compression ratio
Hey guys I'm really ignorant about engines. All I know is I like to wheelie and go fast haha. I currently have a little 88ci 2006 fxd and I've been beating the hell out of it. And I'm ready for more power but I'm on a budget. I have a guy that is going to. do my build just going with a SE 95" kit with the 203 cams that are included in the kit. My mechanic is recommending I do a 30 head gasket and mill the head down .025 he says that combo will help raise the compression ratio. He is also doing a mile port and polish.
I have a buddy with a softail he has a 95" with 10.5:1 comp and it's a bitch to start sometimes. I was wondering where I would be in relation to his bike
I have a buddy with a softail he has a 95" with 10.5:1 comp and it's a bitch to start sometimes. I was wondering where I would be in relation to his bike
HDF Community Team
Joined: Jun 2006
Posts: 12,763
Likes: 2,597
From: san antonio
Your builder has it about right but why not just bore your cylinders, install SE cast flat top pistons, use the .030" head gasket and SE204 cams or an aftermarket like Andrews 48 or 37. The '06 heads flow better than earlier heads and don't require much work; just some cleanup, bowl blending and a good multi angle SERDI valve job.
Boring your cylinders and buying SE cast flat top pistons will be cheaper than buying the Stage II BB HD kit and doesn't lock you into the SE203 cam which is not such a good pick for a Dyna. The SE kit components are not "matched" so your builder should torque up the cylinders in torque plates and check piston to cylinder fitment before assembly; if out of spec, he can return the parts. Not an issue when boring your seasoned OEM cylinders to fit a new set of pistons.
Boring your cylinders and buying SE cast flat top pistons will be cheaper than buying the Stage II BB HD kit and doesn't lock you into the SE203 cam which is not such a good pick for a Dyna. The SE kit components are not "matched" so your builder should torque up the cylinders in torque plates and check piston to cylinder fitment before assembly; if out of spec, he can return the parts. Not an issue when boring your seasoned OEM cylinders to fit a new set of pistons.
Thread Starter
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Tourer
Joined: Mar 2015
Posts: 301
Likes: 1
From: las vegas
Your builder has it about right but why not just bore your cylinders, install SE cast flat top pistons, use the .030" head gasket and SE204 cams or an aftermarket like Andrews 48 or 37. The '06 heads flow better than earlier heads and don't require much work; just some cleanup, bowl blending and a good multi angle SERDI valve job.
Boring your cylinders and buying SE cast flat top pistons will be cheaper than buying the Stage II BB HD kit and doesn't lock you into the SE203 cam which is not such a good pick for a Dyna. The SE kit components are not "matched" so your builder should torque up the cylinders in torque plates and check piston to cylinder fitment before assembly; if out of spec, he can return the parts. Not an issue when boring your seasoned OEM cylinders to fit a new set of pistons.
Boring your cylinders and buying SE cast flat top pistons will be cheaper than buying the Stage II BB HD kit and doesn't lock you into the SE203 cam which is not such a good pick for a Dyna. The SE kit components are not "matched" so your builder should torque up the cylinders in torque plates and check piston to cylinder fitment before assembly; if out of spec, he can return the parts. Not an issue when boring your seasoned OEM cylinders to fit a new set of pistons.
HDF Community Team
Joined: Jun 2006
Posts: 12,763
Likes: 2,597
From: san antonio
My budget is. Around 2k I can get the se kit for 1k. Labor is going to run me 7-800 I have a pcv for tuning already. And dyno tune is going to cost me 100$ I'm getting the labor and tune done cheap (atleast imo) lol. Because I bring alot of work into my mechanics shop so he always cuts me a deal. If boring my stock cylinders and buying se flat top pistons will save me money I'm all for it! But how much would u say it saves? And thanks again for the reply.
BTW, you might consider installing compression releases as part of the head work. The $400 you might save on the piston/cylinders is almost enough for a basic "street" port on your heads.
Last edited by djl; Feb 11, 2016 at 12:38 PM.
Thread Starter
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Tourer
Joined: Mar 2015
Posts: 301
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From: las vegas
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HDF Community Team
Joined: Jun 2006
Posts: 12,763
Likes: 2,597
From: san antonio
You need to focus on corrected CR and/or CCP; the motor (sorry Scott) does not see static CR. The motor operates on dynamic (corrected CR) which are functions of the timing of the close of the intake valve. Static could be 10:1 but with low CCP and lagging power in the low to mid range. Install cams with an earlier intake close and static stays the same but CCP increases. Compression = torque.
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Cruiser
Joined: Mar 2014
Posts: 130
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From: Eagle River, Alaska
I haven't had the bike on a dyno, so I couldn't give you any numbers, but I'm very happy with the power the engine is making. Happy enough in fact, that I may never even bother to dyno it, but we'll see...
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