What about port matching? : V-Twin Forum: Harley Davidson Forums

Gaff · 11-28-2012, 05:03 PM

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?

wfolarry · 11-28-2012, 07:24 PM

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.

**dsvracer** · 11-29-2012, 07:38 AM

i agree with Larry.

BVBOB · 11-29-2012, 07:45 AM

Quote:

Originally Posted by wfolarry

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.

**KingofCubes** · 11-29-2012, 09:01 AM

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.

Gaff · 11-29-2012, 04:52 PM

Very good answers, thanks.

claydbal · 11-29-2012, 09:46 PM

Depends on how much beer ya got. Wut they said.

**KingofCubes** · 11-30-2012, 11:25 AM

Quote:

Originally Posted by claydbal

Depends on how much beer ya got. Wut they said.

Dennis, where have you been hiding, any new girl friends?

claydbal · 11-30-2012, 12:14 PM

Hey randy. Yu know it! The current one tastes like possum.

Uncle Salty · 11-30-2012, 01:09 PM

Better trade that one in for a newer model.

claydbal · 11-30-2012, 09:15 PM

Lol. Hey unk! You know its like wine man.

Rollmeaway · 11-30-2012, 09:41 PM

& another perspective ...

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

You Tube

You Tube

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

Enjoy

torqueinc · 12-01-2012, 02:36 AM

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

Gaff · 12-01-2012, 05:41 AM

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.....

Chief Davis57 · 12-01-2012, 06:59 AM

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?