BBC output overview.

[user-17438]

OK you head porters out there. I have just been playing with an
Edelbrock big port head (started life at about 355-365 cc) I have ported one of each port looking only at the airflow gains with the intent to get the most that is practically possible. At this moment in time I have 452 cfm on the good port and 433 on the bad port at 1.150 valve lift. Good port vol is 384 cc and the bad 380 cc.
Valve is still 2.3.

Any comments on this before I throw in my $2 worth of thoughts?


DV

What head?

Don't have a part # - Edelbrock is still trying to identify a match would you believe!
Anyway here are some shots that might help.
DV

That's the Victor 24 casting. I have lots of flow data for different sizes of that casting. 345cc - 390cc. Fun head to work on. Stupid fast if you want. Lol

2.400/1.850 0work on the seats. Otherwise your throat will be huge on the exhaust if you go smaller.

[David Vizard]

What head?

Don't have a part # - Edelbrock is still trying to identify a match would you believe!
Anyway here are some shots that might help.
DV

That's the Victor 24 casting. I have lots of flow data for different sizes of that casting. 345cc - 390cc. Fun head to work on. Stupid fast if you want. Lol

2.400/1.850 0work on the seats. Otherwise your throat will be huge on the exhaust if you go smaller.

MT,
How about some flow numbers and port vols that achieved such.

Did the 2.4 inch intake get tangled with the 1.85 valves too early to use a lot of overlap?
Thanks
DV

[gowest]

Hope your recovery goes well David. Would be nice if aftermarket parts worked as well for us as it does engines !
Are you still planning to make Race Engine Challenge ? Time is getting pretty thin.

[David Vizard]

Hope your recovery goes well David. Would be nice if aftermarket parts worked as well for us as it does engines !
Are you still planning to make Race Engine Challenge ? Time is getting pretty thin.

Thanks for your kind wishes. AS for the REC I covered my position on that in the initial post.
Thanks
DV

[jed]

There's some pretty interesting work in the chamber as well. I like it

Yes very interesting chamber. Resembles a soft head (maybe maybe not). Could you show us the piston top please.

[Erland Cox]

Erland,

Here is a graph of the curtain area per cube displacement. 2.62 only beats out the 2.02 in the 350 above .25 D. At all other points below the .25 D for the 2.02 it is exactly equivalent.


DV

David, a big block has 1,7 rockers to lift its valves faster because it is a bigger engine.
You must compare real valve lift curves.
If a 2,02 valve lifts ,500" a 2,3" valve must lift 0,570".
Then the 2,3 valve gets a 30% greater curtain area equialent to the displacement difference.
If a small block har ,500" lift / 1,5 X 1,7 = ,567"

Erland

[Erland Cox]

OK you head porters out there. I have just been playing with an
Edelbrock big port head (started life at about 355-365 cc) I have ported one of each port looking only at the airflow gains with the intent to get the most that is practically possible. At this moment in time I have 452 cfm on the good port and 433 on the bad port at 1.150 valve lift. Good port vol is 384 cc and the bad 380 cc.
Valve is still 2.3.

Any comments on this before I throw in my $2 worth of thoughts?

DV

Fantastic flow for a 4,25" bore.
2,3" intake valve seems big to me for that bore and 2,4" will probably hit the cylinder wall.

Erland

[David Vizard]

OK you head porters out there. I have just been playing with an
Edelbrock big port head (started life at about 355-365 cc) I have ported one of each port looking only at the airflow gains with the intent to get the most that is practically possible. At this moment in time I have 452 cfm on the good port and 433 on the bad port at 1.150 valve lift. Good port vol is 384 cc and the bad 380 cc.
Valve is still 2.3.

Any comments on this before I throw in my $2 worth of thoughts?

DV

Fantastic flow for a 4,25" bore.
2,3" intake valve seems big to me for that bore and 2,4" will probably hit the cylinder wall.

Erland

Erland,
This was on a 4.5 inch bore.

DV

[David Vizard]

OK you head porters out there. I have just been playing with an
Edelbrock big port head (started life at about 355-365 cc) I have ported one of each port looking only at the airflow gains with the intent to get the most that is practically possible. At this moment in time I have 452 cfm on the good port and 433 on the bad port at 1.150 valve lift. Good port vol is 384 cc and the bad 380 cc.
Valve is still 2.3.

Any comments on this before I throw in my $2 worth of thoughts?

DV

Fantastic flow for a 4,25" bore.
2,3" intake valve seems big to me for that bore and 2,4" will probably hit the cylinder wall.

Erland

Erland - it was a 4.530 bore.

DV

[David Vizard]

Back to same flow figs and port comparisons.

At the end of this post you will see the flow of the weird shape port Vs the rectangle port of the big port Edelbrock head. These are 322 and 382 cc respectively.
The thin graph lines are the Big port Edelbrock head (blue intake and red ex) The thick lines are the 322 cc weird port. The tests shown here go tyo 1 inch lift and at this point there was little difference in total flow of either head. However above 1 inch the Edelbrock heads port kept increasing flow up to 452 cfm at 1.150.
On the other hand the 322 cc weird port topped out at the 1 inch point and still only flowed 433 at 1.150.

Based on just the flow figures these two heads don't look that much different in the up to 1 inch lift range.
Sure the exotic port is better in the 500 to 800 lift range but though significant it's not a super deal.

Take a look at the graph and then we will move on into that territory that encompasses the (incorrect) term ' a flow bench can only tell you so much'

I am going to show that such a statement is only dependent on how well you can read!!

DV

[David Vizard]

Whatcha selling?

At the moment I am dispensing a free cure for ignorance!
DV

[408 Nova]

Good to see you back Dave. Now about that third big-block Chevrolet book...you gotta write it! Just kiddin man, I hope you're doing well.

[cjperformance]

Whatcha selling?

At the moment I am dispensing a free cure for ignorance!
DV

[ozyfordman]

X2

[Geoff2]

X3