[62fatcat]

i have been playing with my test head thought i might try this for next season.
comb, 447"pontiac, f-2 procharger-27#boost, blowthrue 850cfm CSU carb.
for this season the intake ports on the car were 235cc, with a 1.20" x 2.40", and a port matched victor intake.
so,
if i use a victor-wide port intake, along with the added increase in head port volume(15cc). that all of that cc of mass/liquid could translate into a ton of velocity at poshrod bulge, and subcsequntialy throuh the rest of the port.
maybe i am just waisting my time?

thanks for any input.
brad.

[Jim Robertson]

Move the pushrod...you will be glad you did. Or send them down and we will...

:-)

Best of luck,
Jim

[62fatcat]

thanks,
that was very helpfull.

[blaktopr]

It's never a waste of time trying to do better for yourself. By how I am reading this you could be right, but it's hard to tell without knowing the rest of the port, where you would be putting the extra 15cc. Based on the numbers of the intake opening you stated, your pinch may be around 2.6's through and even less after it as the floor and roof converge, 2.4-2.5?? accounting for corner radius, At 330 cfm it gets pretty fast to the ssr. Make a mold Brad. The stuff is cheap and tells you tons. No need for the wide port intake. Don't worry so much about the opening size. Work those 15cc's inside where it counts.

[62fatcat]

thanks for the info blaktopr.
i spent most of my time on the roof and widening the short turn

i got some flow numbers on the port.
2.11" valve, 28", and a 4.20" bore.

.1" 76 cfm
.2" 150
.3 212
.4 261
.5 293
.6 317
.7 335
.8 344

[Region Warrior]

Now your talk'n!

[440GP69]

If you don't move the P-rod don't open up the entrance any wider than it starts out, The choke Point is still there so making the head larger before the pinch does little for you, Fwiw, Good flow numbers, Dividing CFM to Runner Volume is good when comparing similer or like cylinder heads fwiw

[65nss4spdGTO]

Brad,

What size is the cross section just under the valve seat?

Calvin

[62fatcat]

Calvin,
it is 2.008"

[blaktopr]

OK Brad. That 2.008 was measured at the smallest part of the seat at around the bottom cut or ? If that is your smallest part after the ssr right where the seat begins of a tad furthur but not part of the 45 seat cut then you are too big there for the valve you are using. That number shows me why the flow curve looks the way it does The more you open that area, the more the valve is not in the way changing the flow and port characteristics. I don't think anyone is running a 95% throat to valve ratio. Don't grind there no more. Your only tricking the bench. You should be in the 1.8 to 1.9's

As for moving the pushrods, who says the tubes have to be round?

These numbers are engrained in my mind. This may help.

FPS=(CFM*2.4)/Cross Section Area

You can measure parts of the port, subract the radius or try multiplying port size LxW by .95. This will give you close numbers for the CSA

For AVG CSA of the whole port. CC it, Then find the length with tape. Roof and floor and then divide by 2. Take the length, (5.1 to 5.3 probably) and CC and do this.

AVG CSA=(port CC)/(port length*16.387)

So if say you had these numbers...
235CC
5.2" centerline length
Your 2.008 "throat" 3.08 Sq in A
Your 1.20x2.40 entrance 2.88*.95=2.73Sq in B
Your possible pinch about 1.070x2.30 2.46*.95=2.33Sq in C
Your possible after pinch at 1.2x2.1 2.52*.95=2.39Sq in D
SSR apex at 2.9 square in E
317 CFM@.600
AVG CSA = (235)/(5.2*16.387)
AVG CSA= 2.75
FPS= (317*2.4)/2.75 FPS=276
FPS A=247
FPS B=278
FPS C=326
FPS D=318
FPS E=262
These are all "calculated" numbers of port centerlines of the whole or pieces. Not what you may measure throughout the port but enough to help.

Plus I am trying to make you think a little, of a bigger picture, to get you car going faster for yourself.

[65nss4spdGTO]

Originally Posted by 62fatcat

Calvin,
it is 2.008"

Brad,

Have you tried a 2.190 valve? Most of the heads I've work will have a throat around 1.900 to 1.970 using a 2.190 intake valve. I think a 2.190 valve would help and try to make the port as tall as you can.

Calvin

[BruceWilkie]

Hey Chris

At the extreme velocity his 27 psi is already creating would you just want the straightest path possible vs venturi effects?? Really curious about this.

[62fatcat]

thanks for the input guys, i apreciate it.

[62fatcat]

blaktopr,
I was going over the info in this thread again.
I was wondering what you recomended for the push rod tubes, that are not round??

Thank you for any input!

Brad