Mike Lewis head porter

Oh, you're that Steve!

Joe, It would be nice to get the heads flowed, just have to find a place. Lancaster is do-able, about 2 hrs west of me. I'm between Philly and Allentown. I'll ask my machinist when I drop the heads off.

 

it will tell us all a lot. I am sure they will flow really well. would eliminate any concerns about head performance.

 

looked at that chart over the years always at the intake numbers. just notice the exhaust numbers on Magnotti heads are the best wonder what size exhaust valve.

 

Found an older thread (2009) that Roger (aka Riv1964) posted on his diy port job.
He used 1.94 Manley Intakes and got some great numbers.
https://v8buick.com/index.php?threads/nailhead-head-porting.167546/page-2

 

if going with after market push rods or not i would open the push rods holes a little.

 

Unfortunately you can't just use the common/ standard valve opener that works on a ton of heads to do a flow test on Nail heads.
I had to spend 2.5 hours to make a adapter to bolt my valve opener to so to be able to do a accurate flow test on these heads.

 

These last posted Intake flow numbers are good, but for a flow test done @ 28" the port velocity is too low .
One needs to keep in mind that your moving a long mass of air from the Manifold plenum into the cylinders, and in a idle world that air mass would be large enough to fill the cylinder.
The problem is moving that air mass takes time and the higher the rev's the faster that air mass needs to move to fill a cylinder.

The start of the limit for this Intake flow wise in a NA motor is 550 fps at standard temp and pressure.

When testing for velocity at the Intake flange at max lift for the Cam that will be run I like to see a minimum of 325 fps , that's for a flat out race motor that is geared to its Cam well, and then no more then 375 on the other side of the coin.
For a 80% street 20% strip motor that needs a wide power band to make up for less then idel gearing I might want to see a peak number of 425 fps.

 

will low velocity hurt at the upper rpm ?

 

Is this measured at the inlet to the head (Intake flange)?
Velocity would vary depending on where in the port it's measured. Can be faster in center, lower at wall, etc.
And it would be faster in the narrower 'pinch point' before to goes to the larger bowl, where velocity needs to slow to make the turn to the valve opening.

I would think more cfm= higher velocity unless the cross section area of the port is enlarged.
But to provide enough flow for rpm's over the stock limit of around 4800 rpm, the area at the pinch point needs to be opened up a bit.

I'm trying to learn, tell me if I'm on the right track.

 

Steve, what 'velocity' in the chart what you are referring to? I only see 'valve velocity' which is no where near the 325-425 fps you mentioned.

You mentioned 'velocity at the intake flange'. I assume this is the average velocity of the air entering the port.
I believe I see your point....
Take 2 different guys, one an experienced guy that knows how to massage the port just right, and an amateur that goes in and hogs more material out. Both get 220 cfm flow @ 0.050", but the experienced guy gets 375 fps avg velocity and the amateur 'hog-out' gets 275 fps.
The higher velocity 375 fps would perform better at all rpm ranges.
Would both perform similarly in 1/4 mile race use? (as Joe asked)

 

Painfully slow is an understatement!!!!!!

 

Many times I see where somebody has paid for a service such as an engine build or head porting or something along that line and paid up front and the person performing the work dies whether it be old age or illness and the customer is out of luck. I will never put myself in a position to not have some form of recourse should things go wrong.