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Old 11-28-2012, 05:03 PM   #1 (permalink)
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What about port matching?

I've done alot of searching on the subject and all I've found was just in casual speaking that it needs to be done.

Why not as much talk about port matching as there is on head porting?

Harley leaves a hell of alot to be desired in port matching, honestly.....

Isn't there as much CFM gain in port matching, valve seat blending that there is in a street port?
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Old 11-28-2012, 07:24 PM   #2 (permalink)
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Port matching for size is important. Using 1.8 ports with a 1.625 manifold will kill you. Port matching when they're both the same size makes it look nice but you won't see any improvement on the dyno. The little edge you see makes you think that you're losing airflow when in fact it might be helping to reintroduce fuel that has fallen out of suspension or help the air to reattach itself to the port wall. There's a lot more going on in there to worry about than a little protrusion in the port.
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Old 11-29-2012, 07:38 AM   #3 (permalink)
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Thumbs up

i agree with Larry.
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Old 11-29-2012, 07:45 AM   #4 (permalink)
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Quote:
Originally Posted by wfolarry View Post
Port matching for size is important. Using 1.8 ports with a 1.625 manifold will kill you. Port matching when they're both the same size makes it look nice but you won't see any improvement on the dyno. The little edge you see makes you think that you're losing airflow when in fact it might be helping to reintroduce fuel that has fallen out of suspension or help the air to reattach itself to the port wall. There's a lot more going on in there to worry about than a little protrusion in the port.
Larry, the general consensus was always to have a smaller intake so the air wouldn't hit that "lip" but a while back you explained it to me on the phone and it makes perfect sense about the smaller air column slowing down as it hits the bigger port.
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Old 11-29-2012, 09:01 AM   #5 (permalink)
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Waterfalling, as BVBOB explains can be a bad thing. Also, when we had a flow bench here and created a little air gap in an inlet collum the cfms would often climb. It helps to remember that in most instances the air is lazy at the wall.
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Old 11-29-2012, 04:52 PM   #6 (permalink)
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Very good answers, thanks.
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Old 11-29-2012, 09:46 PM   #7 (permalink)
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Depends on how much beer ya got. Wut they said.
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Old 11-30-2012, 11:25 AM   #8 (permalink)
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Depends on how much beer ya got. Wut they said.
Dennis, where have you been hiding, any new girl friends?
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Old 11-30-2012, 12:14 PM   #9 (permalink)
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Hey randy. Yu know it! The current one tastes like possum.
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Old 11-30-2012, 01:09 PM   #10 (permalink)
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Better trade that one in for a newer model.
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Old 11-30-2012, 09:15 PM   #11 (permalink)
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Lol. Hey unk! You know its like wine man.
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Old 11-30-2012, 09:41 PM   #12 (permalink)
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& another perspective ...

http://www.v-twinforum.com/forums/tw...nder-port.html


now I know this engine is not totally realitive to a harley intake but think ahead it is a scientific formula that applies to all intenal combustion engines.... I mean we were doin this chit back in the 70's without computerization go figure


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Old 12-01-2012, 02:36 AM   #13 (permalink)
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Cannot believe that Branch still polishes the intake ports and manifold ports much less does all the welding to the combustion chamber to make the head worse than it was before.

They also cut between .070 and .080 off the deck

I have a set of early twin cam heads that you could pop the seats out with a screw driver,the customer still has not picked them up
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Old 12-01-2012, 05:41 AM   #14 (permalink)
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Well the reason I ask the question was that your always looking for a seamless flow thru the transition points, no matter what the engine.
In breaking down my engine I noted the off set of the carb to the intake and then the off set of the intake to the head, it just struck me as pretty crappy port matching.

But not realy in tune with performance and harley's I'm finding that a lot of things I've found on other high performance bikes I've had through the years don't apply to harley's.

I understand the explination, just goes against what I've learned through the years, but it isn't the first thing that done that to me either.....
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Old 12-01-2012, 06:59 AM   #15 (permalink)
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This is all very interesting reading but what were the engineers thinking when they designed the heads in particular the ports, or should we say ports relative to valve size, and stock cam lift? All of which I would have thought would work together for maximum air flow efficiency. I could also see making changes to port size or shape if increased air supply demanded it. What do the aftermarket performance heads look like in this area?
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