Porting feedback

[broken-wheel 659]

I've taken 2mm out of the aussie speed and still got it to flow within 2% across all ports, low lift flow down not relate to low rpm punch at all, the aussie speed manifold is good but it's not made for people who port above 185 cfm, it's mainly aimed at basic cleaned up ports and mild flat tappet cams, you want more you have to look at making if flow a little more.

 

You are not going to get a crossflow to flow past 220 cfm while making power and expect it to behave, that's simply silly. If you want low rpm punch then buy a TDI, else use gears, that's what they're there for, on my gti I never get past 4th through the mountains, it's mainly 3rd and 4th and some corners a quick bump to 2nd.

 

nothing wrong with that head, you just use a dual pattern cam which everyone here hates.

[Mustardxf 29]

 

 

nothing wrong with that head, you just use a dual pattern cam which everyone here hates.

How do you know I run a dual pattern cam?

[broken-wheel 659]

because whoever ported that head for you would of recommended a dual pattern cam with longer exhaust duration out of courtesy 

[slydog 7,873]

And the longer exhaust will most likely just leave part of the previous cycle in the bore/chamber anyway which is not good. Still needs to be able to flow good enough to use it.  

[ando76 4,354]

Yeah not sure I agree with you on your summation of the aussiespeed manifold broken wheel.  I run one on the burnout car on a head that flows 193cfm and its basically untouched.  The ute makes 255@ the treads on the toughest dyno in town.  It wouldn't make that if the manifold wasn't right.

 

A lot of people get hung up on airspeed on the flow bench and making improvements to get the biggest number on the bench.  I have no problem with this as long as the low lift gains are not destroyed in the process. 

 

It is important to understand that the flow bench is a constant pressure - not at all like what actually occurs inside the engine.  A head that shows good low lift airspeed gains will almost always out perform what the bench says it will.  Why.  Because the rush created in the low lift areas is enough to overcome the 'restriction' in the manifold up top.  Seen it way too many times not to believe it.  What did old GT like to say 'You want the smallest port, doing the biggest job". 

 

Good low lift airspeed gains equates to good torque early on the dyno and with the right tuning the torque can be maintained.  That's what makes a punchy (torquey) engine off the bottom.  When you get this right the difference under foot is so noticeable.  The things are just so grunty.

 

When my ute was on the dyno, old Cliff just kept repeating how strong the engine felt.  He had it on the hardest ramp rate and he just kept saying that the ute was eating it. 

 

Oh and for the record - I have absolutely nothing against dual pattern cams.  My 'holy roller' cam is dual pattern.  Nothing wrong with them if used correctly. 

 

Oh and next time your at the flow bench - put a carby on top of the manifold and wire the throttle open and have a look what that does to your flow figures.  Even just put a good 4 hole carby spacer on top and watch what happens.  Very scary indeed. 

[PRO250 1,506]

While where talking about it whats peoples ideas on how far you can blend back into the valve seat I had a 3 angle set cut done on a head I did a little while ago and he did make the comment that he did think I went to far ive got 4 other heads that ive done that are just as far. Now im a unsure if I just made it harder for him to cut the seats or he thort the seat will fall out of the head or what as I was in a hurry that day and did not have time to talk about it

 

[ando76 4,354]

I see no problem whatsoever in moving into the initial part of the actual seat where it meets the throat.  Sometimes it is necessary to get correct throat percentage.  On the Holden heads I just did I had to step into the seat a bit, but I did it on the high speed side and left the short turn alone. 

Cam does my seat cuts and he has no issues with stepping into the seat a fraction - especially if it is to get the throat percentage up.

It is more common to have to step into the seat on a single seat cut.