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Stock heads what's too much milled off?

Started by ReapersWG, September 15, 2020, 01:56:15 PM

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ReapersWG

Found a set of heads that were ported but the guy that has them for sale says they measure 70cc now I know 83cc is stock. He ran KB flat tops. He said the KB pistons even though flat top were .8cc? Thought most flat tops were -1.5cc? Even with flat tops at 70cc I would think there would be a risk of piston to valve clearance especially running a .030 HG. He also said his build had a .028 squish. Thought .030 was the lowest most would wanna go with a street carbed evolution. Thanks

thumper 823

I know nothing most the time but my guess is you are way way safe
Unless you are running all sorts of lift/overlap.

Measure and you will know.
D Troop 3/5, - C/16 ,162AHC, Mekong delta.
Rising from the Ashes  UHIH

ReapersWG

I'll be running a Woods W6H cam. Have Jim's rollers new tappers from Larry and brand new S&S tappet blocks. I am milling the pistons a little to achieve zero deck height with a 030 HG. With my current heads which are 73cc I'd be in the 9.8 to 1 range but I know the 6H likes 10.2 so if I used these heads I'd be much closer. I'm also wondering about the Keith Black flat tops. Online says they are +.8cc but then they list their domed pistons - vs everyone else lists their domed + example 12.9cc on a Weisco and a KB domed lists -9.9cc for a domed piston. Just want a little clarification I'm not engine builder thanks

Don D

Sounds like a candidate for compression releases

ReapersWG

Ok let me ask this my heads measure 74cc can I have them milled to 70cc without any issues? I already have releases

Hillside Motorcycle

Quote from: ReapersWG on September 15, 2020, 07:13:12 PM
Ok let me ask this my heads measure 74cc can I have them milled to 70cc without any issues? I already have releases

May need to surface intake manifold pads, and increase valve reliefs in the pistons.
Otto Knowbetter sez, "Even a fish wouldn't get caught if he kept his mouth shut"

Don D


aswracing


Hillside Motorcycle

3.750" is the O/A dimension for the thickness of OE Evo, and T/C heads.
Otto Knowbetter sez, "Even a fish wouldn't get caught if he kept his mouth shut"


Hillside Motorcycle

I disagree.
I have measured them more times than I can ever remember.
That dimension is in fact 3.750", unless a mis-machined from HD.
A Screaming Seagull performance head will usually measure 3.690". (minus .060"), and the intake pads are also cut deeper. :smile:
Otto Knowbetter sez, "Even a fish wouldn't get caught if he kept his mouth shut"

Buglet

   Have a set on a bike that measures 3.590 no problem fitting. being running for ten years plus. All the stock ones seam to measure 3.750, had a couple old ball ones that measure bigger.