[Half-Inch Stud]

Originally Posted by Half-Inch Stud

My Manifold thoughts are to grind the Manifold Dividers "paper-thin" an inch or more in, to improve the flow trajectory past the ported-pushrod-bulges. I plan to inspect that on me manifolds.

Enhancing my already-clear Post: Grind the Manifold divider, not the Head divider, for Flow trajectory improvement past the Pushrod bulge.

[steve25]

Grinding the common wall at the flange like that only helps out the inboard ports to provide more area, on the out board ports its the push rod buldge that piches things down.

In regards to testing above 28", no as my Super Flow bench (the 110 model like Jim Hands and Rock from HHP mag) can only do a max of 15"h20, we than have to do the math to convert up to 25 or 28".

[fasteddy]

I am not totally sure, but I think "Oinky" has hung up the grinders and wrenches. Health reasons. He will still talk your leg off if you call him. If you have a Pontiac question, he is always willing to help.

[Half-Inch Stud]

Originally Posted by fasteddy

I am not totally sure, but I think "Oinky" has hung up the grinders and wrenches. Health reasons. He will still talk your leg off if you call him. If you have a Pontiac question, he is always willing to help.

Say it isn't so.

Yea okay, Good Point. inner CYLs 3 4 5 6 benefit from grinding Manifold divider per me prior Post claim). I was thinking the outer CYLS 1 2 7 8, would benefit depending on the intake runner trajectories.

[tc]

Mr Half. I have ported to the felpro 1233 gasket size in the past ( 1.18 wide ) but a few years later decided that staying with less width is better (this is the street forum ).

I know years ago the some stock class racers, where you could not port the heads, would build up the intake manifold port to match the width at the bulge in the head. Making the smaller width a more gradual flow path instead of the bump at the bulge.

Many years ago I spoke with Pete McCarthy and he told me not to port the bulge at all. The idea is to have only one venturi in the flow path and he said have it at the bulge.

Jim Hand also told me the bulge is not much of a restriction, just reshape it. Again, thank you Jim for your help.

[steve25]

Let me detail more my reply on the FPS question some post back on this thread.

460 FPS would be concidered fast, too fast for a race only motor looking for a 1000 to 1500 rpm wide torque peak to hp peak power band.

That being said, for a street/strip motor ( a bit more street than strip and over 3300 lbs)that will not be called on to make more than 550 to 575 hp, then FPS number in the 460 to mid 470 range will work very well.

Again, that being said for a race only motor anything over 350 to 400 FPS dependant on port shape will cut into the torque and hp number that could be had in a 1k to 1.5k power band.

When I have a head for full race use on the flow bench and my peak flow numbers come in along with FPS numbers over the 350 FPS mark I will do what needs to be done shape and/or area wise to get the FPS numbers back in line, EVEN IF IT COST 3% OFF OF THE PEAK AIRFLOW NUMBERS, on the race track the car will be faster!!!

Many times in this situation its best to just slow down the air mass by knocking back the push rod buldge more if you have some left to knock back, but you need to let a velcocity probe guide you in this, by this I mean that dependant on your port width on the roof as you get to the window area, some times kicking back the push rod buldge more top to bottom will put you in a catch 22 situation by where making the this area wider has slowed down the air flow on floor and up to mid port height, but the increase in width from the mid point up to the roof just lets more air mass be admitted and hence the velocity difference between the floor at the crown/apex and roof is now even greater than before!
The result being your back at square one again.

Tom, in regards to Pete`s reply about the venturi area, a more proper term to use is port choke area.
To this regard in a full on race motor you want to have only one port choke in the whole Intake track, and this choke needs to be one stroke lenght up stream from the back of the Intake valve.
To this end and in regards to most stock Pontiac motor stroke lenghts, the choke ends up being in the location of the stock push rod buldge.
Another concideration to the max race motor is that this area from the back of the valve to the choke needs to contain the volume needed to fill the cylinder to atleast 100% VE.
Things start to get real crazy now math wise as you might invision!

[tc]

Steve,

You amaze me. Thank you for sharing yet another useful tip on the seemingly secret head porting technique. Just how many more do you have?

Many years ago the Pontiac was put down as a car/engine that was not fast, you older guys remember this. We had the heads, just not the knowledge to make them flow better. I wish I had properly ported heads back in the old days of young guys street racing.

Thanks again, Steve

[steve25]

Alot of these so call secrets where very kindly pass on to me by others so I`am just sharing, and hopefully doing the same good!

In some magazines and forums this info is referded to as tricks so as to generate sales.
That really pisses me off as the word trick infer`s magic, and their is no magic in making a car perform better above a certin HP level, you eitheir know what your doing or you do not and have to refere to other folks level of info to step you up to the next performance floor!
I too got into porting back in my younger days to keep up with my buddys cars that both had less lbs to drag around had heads that flowed way better than the 389 heads I had on my boat of a 65 GP.
I remember all too clearly saying to myself that with the amount of time I put into porting (grinding with a electric drill and some stones, lol) some 670 heads that I picked up for the motor that surely I now had some killer flowing heads!!

I came to find out that once I got my flow bench and testing those same 670 heads that a measly 230 CFM, or plus 25 was all I got extra out of them on the intake side.
Now lets fast foward to your heads Tom and on your first guided try picked up 75 CFM!!
It`s good to have friends no?