So, if I'm understanding the previous low-flow comments, the port velocity is determined by the smallest cross sectional area (CSA) of the port, which in this case is the pinch point around the pushrod tubes. If I use a set of machinists dividers to measure and compare this pinch point, the #7 heads and the ProComps will have approximately the same CSA?

 

What did the ports opening measure? Even if it 190CC, it will be fine. Olds is a torque motor, tough to kill the bottom end power.

 

I'm going to my shop this afternoon to size up the port differences between the stock #7s and the ProComps. I'll post my findings here.
Rodney

 

I didn't make it to the shop this weekend but managed to run by after work today. Here's what I learned as I compared the ProComp heads to a stock pair of '72 7a heads. First, the raw data:

Intake port size (at gasket surface)
7a - 1.31"x2.0" CSA=2.62 sqin
PC - 1.44"x2.5" CSA=3.60 sqin

Intake runner size (at smallest pinch point)
7a - 1.08"x1.83" CSA=1.98 sqin Vol=160cc
PC - 1.06"x1.63" CSA=1.74 sqin Vol=188cc

Although the intake port opening (at the gasket surface) is larger than the 7a heads, the ProComp runners are actually smaller when measured at the smallest point. The ProComp intake runner appears to have a raised floor whereas the 7a floor is more flat, and the ProComp roof drops gradually into the bowl whereas the 7a slopes upward from the port opening and then gets smaller at the bowl.

Here's a questions for the engine builders (remember I'm not building a big-*** race motor). The Edelbrock 7111 intake manifold ports are only 1.22x1.88". Is it absolutely necessary to open these up to match the ProComp ports, or is the mis-match OK? I guess there could be some turbulence because of the larger port in the PC heads. Would this have any adverse effects on the air-fuel mixture as it moves through the intake tract?

 

Builder said he saw no need to port match intake on my RPM w/ Ed heads. I think there would be improvement to top RPM range if matched but for street driving I guess it wouldn't do much.

 

Sensei, tell me more about this Honda rodded, 385 cid, SBO stroker! LOL. I'm thinking 10 more cubes can only help in my pursuit of torque and should work even better with the ProComp heads. Are these Honda rods from a 4-cyl engine? The 2013 Scat catalog lists a Honda, 4340 H-beam rod that's 5.984" long with a 1.89" journal size for a K24 application. Is this the correct rod for the 385 stroker? I'm guessing that custom piston would be required too. Does the additional 0.100" stroke require more clearancing in the crankcase than the 3.5" stroke? Questions, questions!

 

Eagle and K1 make Honda journal sized rods for SBC with SBC wrist pin sizes in various lengths. That's what he's talking about.

 

I downloaded the Eagle catalog this weekend to check out those Honda-sized SBC rods...boy they are pretty spendy ($$$). Is it possible to get to a 3.6" stroke using oversized rod bearings (for more offset on the crank throw) and use the less expensive 2" SBC rods from Scat?

 

No, no one makes that type of spacer bearing.

 

I rechecked my math behind my last post. I was thinking a 20-oversized rod bearing would allow the extra stroke...but I used .200 instead of .020 - Duh! I guess the decimal point makes a big difference! Can't buy a .200 oversize bearing. Just out of curiosity, What is the largest oversize bearing available?

 

Subbed for info and learning...

 

Pretty sure you are limited to around a 3.5" stroke. My 330 crank is stroked to that, will make my 403 a 425. Get your block sonic checked, see where you can go on the overbore. I thought Scat made rods in the Honda journal? I believe .030" is the max for most bearings but some go .060".