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  #1  
Old 03-18-2002, 10:33 PM
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440dart_72 440dart_72 is offline
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Default header bung question

how important are header bungs for the crankcase ventilation? does it help much? if i weld them on my headers should i do one on each header or just one header. the motor is a 440 in a dart.

thanks for the help
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Old 03-18-2002, 10:49 PM
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I hear they are great, lots of vacuum that is not bled off into your intake, that means more vacuum for the carb, more velocity, more A/F. If you run 2, you will be sucking mostly through each valve cover. If you run one, youll get a good cross flow from the opposite breather through the valley pan, etc. Make sure you baffle your valve covers, you dont want to pull oil into those!
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Old 03-18-2002, 11:06 PM
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ring flutter may decreas and ring seal may be enhanced buy using the evacuation system.However youll get info from moroso's site if you like.Each engine responds a little different,based on leakage past the rings and windage.
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Old 03-19-2002, 10:21 AM
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I just installed a dual set-up on the fish and I look forward to some improved performance. We were developing some pretty big pressures in the crank case with a single breather and pushing oil up into the unbaffled cap. Our first clue was when we blew a cap off on the race track....hummmmm?

You'll never feel a change like this in the seat of your pants, but it may show up on your time slip as a .003-4 improvement....add 4 or 5 of these together and you've cut a couple of hundredths and that's worth it.

I don't like the Moroso clear plastic lines that come with the kit, I used -12 stailess braided line....looks tough, like a couple of ram horns coming off the valve covers.
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Old 03-19-2002, 01:46 PM
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It should theoretically help power by increasing the pressure differential across the piston... the amount of torque your engine makes is due to this differential. The usual way to modify the pressure difference is to increase the pressure on the piston top (higher CR, more air/fuel, etc etc) but decreasing the pressure on the bottom side has the same effect. Of course the pressure on the bottom side of the piston is usually almost zero compared to the pressure on the top side so decreasing the pressure on the bottom typically doesn't help noticeably. If you have high pressures inside the block (like Cuda66273 noticed blowing his cap off) you would notice more of a difference. The top fuel guys used to use vacuum pumps (originally intended for emissions control) hooked directly into the crankcase to evacuate the case, until they found that the breathers hooked into the headers worked better. I think the big reason it has such an improvement on the top fuelers is because they are running such high boost pressures and so have a fair amount of blowby.
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Old 03-19-2002, 09:19 PM
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to expand a little on this theory...

The shape of the piston top ring forces it out against the wall of the cylinder creating a tighter seal on the power stroke. The theory is that if you have pressure on the backside of the ring the opposite occurs causing the ring to not seal tightly against the cylinder wall. Hence losing cylinder pressure and down force to the crank.....

Anyhow that's all I have to say about this....pass the cherries please.
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Old 03-19-2002, 11:08 PM
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Cool good for street engine?

Would this work O.K. on a street engine, or is this strictly race. And if so, how do you hook the line to the valve cover? Pipe tap right in the cover, or what?

What about emissions testing?

Just curious.......Joe
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Old 03-20-2002, 02:55 AM
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The DEQ! The mortal enemy...
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