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These breather bolts are used for mounting the Harley Ventilator AC backing plate. Notice on the threaded side the hole is smaller, just at the end actually. Anybody think to open up the smaller end, drill it out for better air flow? A lot of folks keep these in place and use them as part of an external breather system. Especially in a big bore application, do the head breathers pass more air and would they benefit from opening up the hole in these bolts?
These breather bolts are used for mounting the Harley Ventilator AC backing plate. Notice on the threaded side the hole is smaller, just at the end actually. Anybody think to open up the smaller end, drill it out for better air flow? A lot of folks keep these in place and use them as part of an external breather system. Especially in a big bore application, do the head breathers pass more air and would they benefit from opening up the hole in these bolts?
Ill be following this thread....right now Im figuring out an external breather setup for my 128. I was looking to use these boots along with my S&S Stealth intake...
Ill be following this thread....right now Im figuring out an external breather setup for my 128. I was looking to use these boots along with my S&S Stealth intake...
The stock bolt is very restrictive. I have extra sets of these bolts and did drill out the small end on one set, the air flow change is huge. I wonder if it is worth it AND wonder why the stock bolts are necked down like that.
The whole bore of the bolt is .140", 9/64" ID except for the last 3/32" at the threaded end. I can drop a 9/64" drill bit down almost the full length and just drill out the last bit (3/32").
I want to know what the theory is, why is it metered (restricted) like that.
The whole bore of the bolt is .140", 9/64" ID except for the last 3/32" at the threaded end. I can drop a 9/64" drill bit down almost the full length and just drill out the last bit (3/32").
I want to know what the theory is, why is it metered (restricted) like that.
goofy @$$ guess? possible they want more velocity to spew the combustion goop thru the tubes and into the TB instead of dribble down? that's a stretch I know but what the hell it's raining so reading instead of riding today
goofy @$$ guess? possible they want more velocity to spew the combustion goop thru the tubes and into the TB instead of dribble down? that's a stretch I know but what the hell it's raining so reading instead of riding today
I will say it is thee bottleneck in my external breather system.
Every rubber tube and plastic tee or connector I use has a much larger opening.
Even if somebody was worried about disturbing the Harley "system" you could drill it out just a bit more to 1/8".
Maybe it limits the amount of oil vapor vs air that goes thru the bolts. With the rockers throwing oil everywhere there has to be some splashing going on. Just a thought.
Maybe it limits the amount of oil vapor vs air that goes thru the bolts. With the rockers throwing oil everywhere there has to be some splashing going on. Just a thought.
Seems like there was some kind of planning to the design.
On my 114" I'm only getting some water vapor out of the external vent hose while keeping my oil level at 1/2 up the checked area of the dip stick, I have the new 2020 oil pump on my bike.
The small end hole on the bolt is approx.092", I might try a .125 hole at first and keep an eye on anything coming out of the external vent hose.
Seems like there was some kind of planning to the design.
On my 114" I'm only getting some water vapor out of the external vent hose while keeping my oil level at 1/2 up the checked area of the dip stick, I have the new 2020 oil pump on my bike.
The small end hole on the bolt is approx.092", I might try a .125 hole at first and keep an eye on anything coming out of the external vent hose.
I too run my oil level half way and only get water vapor on my 114, I have a mechanical oil gauge and this level does not affect oil pressure.
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