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Technical Forums => Milwaukee-Eight => Topic started by: Sunny Jim on June 22, 2020, 07:12:31 AM

Title: Heads CC’d
Post by: Sunny Jim on June 22, 2020, 07:12:31 AM
So I had a pair of 107 heads tidied up. The engineering shop measured the chambers at 85cc each after they faced them.  They tell me they faced the heads at .010 .
I am curious as to whether the chamber numbers stack up to only taking .010 off.
I would appreciate your input.
Title: Re: Heads CC’d
Post by: OldMike on June 23, 2020, 12:27:38 PM
Do you know what the stock CC is supposed to be for reference?
Title: Re: Heads CC’d
Post by: Hillside Motorcycle on June 24, 2020, 03:13:56 AM
Depends on what was done inside the chamber ie blending, radius top cut, etc, and if the valves had reversed tulips on them, etc, etc.
Many variables.
Title: Re: Heads CC’d
Post by: Sunny Jim on June 24, 2020, 07:56:35 AM
The heads were standard 107 heads that had been faced. No chamber work or valve work.
The original fly cut marks were as deep as .003 - .004 thou.
The original measurement was 89cc.
After the heads were faced they measures 85cc.
I guess I am trying to equate how many thou removed would give me 85cc.
Title: Re: Heads CC’d
Post by: Don D on June 24, 2020, 09:00:56 AM
What is the head thickness?
Title: Re: Heads CC’d
Post by: Sunny Jim on June 26, 2020, 08:05:48 AM
Quote from: HD Street Performance on June 24, 2020, 09:00:56 AM
What is the head thickness?

I have no idea. Heads are back on.
Title: Re: Heads CC’d
Post by: Don D on June 26, 2020, 08:52:11 AM
That is the fast way to tell what was milled off. So what is the number for the M8? I would have to check a set, 3.750" on most other big twins with OEM heads
Title: Re: Heads CC’d
Post by: KiwiRob on August 19, 2020, 02:22:58 PM
Quote from: HD Street Performance on June 26, 2020, 08:52:11 AM
That is the fast way to tell what was milled off. So what is the number for the M8? I would have to check a set, 3.750" on most other big twins with OEM heads

I get 2.450" ish with verniers on the heads I have here. - Rob
Title: Re: Heads CC’d
Post by: Jmd897 on August 19, 2020, 03:54:56 PM
Mine measured 89cc too.  With my FM kit the compression comes out to 10:75:1.  If i bring it down to 86-87cc I can get a 11:1 but decided that later on I will upgrade the valve springs when I get it milled.
Title: Re: Heads CC’d
Post by: Don D on August 19, 2020, 05:14:26 PM
I have a nice set of springs that are 70lb seat at 1.57 and good for. 600 lift.
Title: Re: Heads CC’d
Post by: Sunny Jim on August 20, 2020, 07:26:16 AM
Quote from: KiwiRob on August 19, 2020, 02:22:58 PM
Quote from: HD Street Performance on June 26, 2020, 08:52:11 AM
That is the fast way to tell what was milled off. So what is the number for the M8? I would have to check a set, 3.750" on most other big twins with OEM heads

I get 2.450" ish with verniers on the heads I have here. - Rob

Just consider the heat when you
Raise that compression.
Title: Re: Heads CC’d
Post by: mike jesse on August 27, 2020, 10:51:19 AM
As a side ?, what are the stock base and head gasket thickness?
Title: Re: Heads CC’d
Post by: KiwiRob on August 27, 2020, 12:46:25 PM
Used set of 107 head gaskets I get 0.043" and base comes in at 0.013". - Rob
Title: Re: Heads CC’d
Post by: mike jesse on August 27, 2020, 05:03:42 PM
Thanks for the info Rob.
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