Board index Flathead Power-Technical Questions, Answers, and Suggestions Big Twin Flatties OOPS!!

OOPS!!

Moderators: Curt!, Pa

Post Mon Apr 18, 2011 5:43 pm

Posts: 536
Location: Wa, USA
Last year I bought a new set of S&S/FHP heads. Since my cylinders are quite heavily relieved, I went for the high compression option thinking that it would make up for the loss from the relieving. I was assembling the valves in the cylinders yesterday and decided to put a head on and check how much valve travel I have. Not enough :cry:.

I am thinking of using a cutter to make the radius of the valve pocket in the head smaller to give more room for the valve. Does anyone see any problems with this? Any other suggestions? I would consider selling these and buying new with different compression if anyone was interested. Trades OK also.

Post Mon Apr 18, 2011 7:28 pm

Posts: 1660
Location: Interlaken, NY USA

The KR racing manual suggested brazing a cutting tool to an old valve inserting in guide, and then turning the valve to gain clearance in heads that lacked a deep enough pocket for valve clearance. Sounds like a back yard fix, but can't be all that bad for them to put it in the racer manual.
DD

Post Tue Apr 19, 2011 7:26 pm

Posts: 536
Location: Wa, USA
Dr.,

Thanks for the reply. I am aware of the remedy you describe. It is a common fix for valve to piston contact in OHV car engines. I have a fixture that I can bolt the head to and tilt it in a mill to match the valve angle. My concern is that reducing the valve pocked radius (sharper corner) will effect flow. Am I overthinking this?

Post Tue Apr 19, 2011 9:13 pm

Posts: 387
My concern is that reducing the valve pocked radius (sharper corner) will effect flow. Am I overthinking this?

Just grind a radius on the tool! :roll:
Robbie

Post Wed Apr 20, 2011 5:14 pm

Posts: 536
Location: Wa, USA
Robbie, thanks for the reply. I am apparently not being clear as to the what I need to know and I don't want to be an jerk about it, so maybe some background is in order. I have been a toolmaker/tool designer for nearly 30 years and have a fairly complete machine shop in my garage. I also have access to CNC if I need it. My problem is not the tool to use or its design. I just want to know if making the radius smaller in the valve pocket of the head will interfere with flow.

Post Wed Apr 20, 2011 5:40 pm
don User avatar

Posts: 573
Location: Spokane WA USA
Leonard Andres used clear heads and smoke flowed his motors to find this answer.
don

Post Wed Apr 20, 2011 6:51 pm

Posts: 536
Location: Wa, USA
Don,

Do you have any idea what his results were?

Post Wed Apr 20, 2011 7:46 pm
don User avatar

Posts: 573
Location: Spokane WA USA
No, but seeing is believing to optimize flow.
Given the "Heavy relieving" that you state, You may not find an easy answer from anyone.
don

Post Thu Apr 21, 2011 4:32 am
jib

Posts: 575
Location: devon,england
why not , get the desired clearance above the valve heads 120 abd 80 if i remember right and then reradius the pockets, thats what i did with the 45 heads after milling then to 6 spec and installing kh cams. regards jib
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years

Post Thu Apr 21, 2011 6:29 am

Posts: 131
Location: BRANFORD, CT

Hi Woody,

I have some old HD instructions on modifing older KR heads to take the latest dome piston.
Valve to head clearance MINIMUM.
Intke = .120"
Exhaust = .080"
Corner radius 1/8"
This radius actually forms a undercut in the head by 1/16 max on the backside of the valve to prevent shrouding.
Good luck,
Bruce
http://www.enfieldracing.com
Bruce Argetsinger
AHRMA Dirt Track # 67J
www.enfieldracing.com

Post Thu Apr 21, 2011 6:19 pm

Posts: 536
Location: Wa, USA
Thanks, Bruce. That is the information I was looking for. It looks like I have a lot of cutting to do. I am using oversize valves and they hit the heads before full lift. If anyone buys the S&S heads, do not get the high compression.


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