Print Page - Head cc question.

Title: Head cc question.
Post by: Jim Bronson on May 17, 2022, 11:35:26 AM

Why would someone select heads with a particular cc number? Is bigger better or is there an ideal cc spec for a given setup?
Thanks.

Title: Re: Head cc question.
Post by: Ohio HD on May 17, 2022, 11:39:13 AM

You need to first know what compression you'll be running at. Then the pistons and head cc volume is set to make the compression you desire.

Title: Re: Head cc question.
Post by: Jim Bronson on May 17, 2022, 11:49:03 AM

Let's say S&S 107, 10.5:1 with flat top pistons.

Title: Re: Head cc question.
Post by: Ohio HD on May 17, 2022, 12:02:10 PM

Need to know is the piston flush with the top of the cylinder.
How many CC's are in the valve reliefs in the pistons.
What thickness is the head gasket.
I'll assume late model 7.659" rods
85cc OEM heads with an 0.030" HG would be "about" 10.2"1 compression.
82cc heads with an 0.030" HG would be about 10.5:1 compression.

But! You need to know the other items I listed above. They all play into the compression ratio.

Title: Re: Head cc question.
Post by: Jim Bronson on May 17, 2022, 12:25:30 PM

I'll need to verify some of the items mentioned. Thanks.

Title: Re: Head cc question.
Post by: Ohio HD on May 17, 2022, 12:56:06 PM

Also confirm if those pistons have a dome or are flat tops.

Title: Re: Head cc question.
Post by: Jim Bronson on May 17, 2022, 01:02:31 PM

Hey I know that one. They are "3cc pop-up dome" pistons.

Title: Re: Head cc question.
Post by: Don D on May 17, 2022, 01:07:41 PM

S&S pistons 110 kit have +.7cc net, just FYI, not 107

Title: Re: Head cc question.
Post by: Jim Bronson on May 17, 2022, 02:11:17 PM

I can't get a 110 kit for 6-8 weeks, so I'm going with a 107 kit.

Title: Re: Head cc question.
Post by: Ohio HD on May 17, 2022, 02:27:49 PM

Drag Specialties shows the S&S 110" kits in stock. Get with your supplier.

I don't know where the 3cc came from. On the web site they do show as 0.75cc for the 110 kit.

Never mind, the 3cc is the 106" S&S kit.

(https://i.imgur.com/2z973nM.png)

Title: Re: Head cc question.
Post by: Ohio HD on May 17, 2022, 02:44:26 PM

I was also mixed up with the 110 and 106 motor.

S&S 106" kit, 3cc piston, 0.030" HG, pistons zero deck, heads 87cc = compression 10.53:1

S&S 110" kit, 0.75cc piston, 0.030" HG, pistons zero deck, heads 87cc = compression 10.57:1

Title: Re: Head cc question.
Post by: Jim Bronson on May 17, 2022, 04:00:15 PM

Keep in mind this is The Peoples Republic, and it is illegal for companies to ship performance parts here that alter the emissions. I happen to be on good terms with a performance shop near here, and they are an S&S dealer. They can order parts and have them forwarded through their 'agent'.

My tech was able to convince them to ship a 107 kit directly to him, and he will return the bad 110 kit. For some reason, they told him that the 107 is a better kit. I don't really care. I am looking to replace the heads down the road, so hence the cc question.

Title: Re: Head cc question.
Post by: Don D on May 17, 2022, 04:52:05 PM

Best 107 kit in my opinion is bored stock cylinders and kb forged lca coated pistons. They are flatops at -1.6cc

Title: Re: Head cc question.
Post by: cheech on May 18, 2022, 07:52:33 AM

Quote from: Jim Bronson on May 17, 2022, 02:11:17 PMI can't get a 110 kit for 6-8 weeks, so I'm going with a 107 kit.

Quote from: Jim Bronson on May 17, 2022, 04:00:15 PMand he will return the bad 110 kit.

:scratch:

HarleyTechTalk

Technical Forums => Twin Cam => Topic started by: Jim Bronson on May 17, 2022, 11:35:26 AM