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I am inching closer to having my Glide put back together for the upcoming riding season. I am almost there, have pretty much the single biggest part of the project near complete, the head work. I have the flow data for them and thought that I would share the information with all of you. There are two charts, Before the head work and after the head work was done. Enjoy!:cool:



 
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heads that the flow drops off at .450 lift wont work that good at all.what he`s saying is,sometimes more work can be done & more air flow can be had,other times,the heads FUBAR`ed.decent heads will have the CFM climb atleast to .600".heads that stop flowing @ .450" will make for a very flat,soft build
 

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What prodrag said sums it up perfectly.
Too much or not enough material removed and or in the wrong spots. Too little is easy to fix. Dewey Jelen (my predecessor) used to turn down the $299 Street Port heads done by others for rework. I will take them all day long. They don't do much to them. The polish doesn't hurt (doesn't help either)

There are about a half dozen things common that can cause what we see and many other not so common ones. Measuring and testing would tell the story plus just a look by an experienced eye. If the person that worked the heads put an oversized valve on the stock seat it would do that. IME one that runs out the back door a little (still increasing flow) at .6 and .7 will work better even if the cam is .5 lift assuming the low lifts weren't murdered to get the top lift numbers and the port is quiet (not turbulent).

YMMV and..
They may be OK
We don't have a clue what was used for test fixtures or other factors that can skew the numbers.
 

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If material has been removed from the wrong areas of the intake and-or exhaust track, you can cause a turbulence that will stall the air flow causing no gains beyond a given lift. Depending on what has been done to the head, it's hard if not impossible to correct the mistake. It may be more cost effective to start over with other heads. A good head porter will be able to make that call.
 

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As Don said, port turbulence, or the fact that they are restricted, will cause that.
You can actually hear that noise, when working with a head that has been "ported", prior to resurecting it.
We've able on many occasions to "pull a rabbit out of our hat" when re-working, others, port work.
Scott
 
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