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BBM head chamber size

April 18 2017 at 4:25 AM
Kimmo  (Login kno1)
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What is the "nominal" chamber size for new BBM heads after the valves has been cut in place? Many Brocks seemed to have around 76cc. Of course the size can be changed quite a bit if needed, but is there a some sort of general size where they usually are. Thanks.

Kimmo

 
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Brent Lykins
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I'm generally around.....

April 18 2017, 4:36 AM 

70-74cc depending on the valve sizes and types. Most are around 70-71.

 
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Blair Patrick
(Login CaptCobrajet)
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Usually 75 to 76cc.......

April 19 2017, 8:42 PM 

The standard package that I use on heads I sell and the heads we prep for BBM "complete" is 75-76cc. Intake valve drop is .200 on a 2.200 intake valve and exhaust .270 on a 1.650 diameter. This works well with my valve job and the valves I had Ferrea make for us. The "drop" measurements may or may not be right depending on valve diameter, margin thickness, and top cuts on a valve job. This is where I settled in on my set-up, so take it with a grain of salt. CC-wise, at those depths, the volume will be close to that. I have milled the BBMs to low 60s with no issue, and even to 58cc on one pair, which was almost .110 milled off. No problem....they are THICK.
Blair Patrick

 
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Kimmo
(Login kno1)
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Reason why I´m asking is...

April 20 2017, 3:47 AM 

that I´m building a 390 stroker for a friend. We will build the short block first. I do have everything else for the rotating assembly (good block included) except the pistons. I need to determine the dish size before I place the order. Heads, cam etc will follow a bit later... happy.gif

Thanks!!

Kimmo


 
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