Fuel distribution in Performer RPM intake

[Joe-JDC]

I have done wet flow testing, sonic testing, and always go back to individual runner testing before finalizing the averages.  IF and I say IF the individual runner is optimized first, then opening up the manifold for all eight runners to flow through the one port, the flow will be nearly identical in flow.  I have tested that on single plane intakes, dual plane intakes, 6V intakes, 8V intakes, and TW, TR, HR 4V, HR 8V, TP intakes, etc., and every time if the one port is properly blended in the plenum, shaped with taper, the individual flow will be the same as all eight open ports.  BTDT too many times to argue any more about it.  I have flow tested Wilson CNC'd $2500.00 intakes that folks were having problems with fuel distribution on, and found as much as 80 cfm difference between end ports and center ports.  I always try to get the end ports on single plane intakes to match the flow of the center ports, and on dual plane intakes I try to get those within 5% of each ports flow.  The RPM mentioned above has a difference of less than 9 cfm between ports in a dual plane manifold that flows 383.27 cfm.  If that is not respectable, than I surrender to anyone who can do better.  Signing off.  Joe-JDC

[TJ]

I have done wet flow testing, sonic testing, and always go back to individual runner testing before finalizing the averages.  IF and I say IF the individual runner is optimized first, then opening up the manifold for all eight runners to flow through the one port, the flow will be nearly identical in flow.  I have tested that on single plane intakes, dual plane intakes, 6V intakes, 8V intakes, and TW, TR, HR 4V, HR 8V, TP intakes, etc., and every time if the one port is properly blended in the plenum, shaped with taper, the individual flow will be the same as all eight open ports.  BTDT too many times to argue any more about it.  I have flow tested Wilson CNC'd $2500.00 intakes that folks were having problems with fuel distribution on, and found as much as 80 cfm difference between end ports and center ports.  I always try to get the end ports on single plane intakes to match the flow of the center ports, and on dual plane intakes I try to get those within 5% of each ports flow.  The RPM mentioned above has a difference of less than 9 cfm between ports in a dual plane manifold that flows 383.27 cfm.  If that is not respectable, than I surrender to anyone who can do better.  Signing off.  Joe-JDC

I don't think anyone is arguing with you.  It's just you're only addressing one piece of the issue.  I clumsily asked a similar question quite a while back and though I got a lot of useful feedback I didn't get to the heart of the matter in the way folks are discussing it right now.  Fuel distribution involves bringing a gas (air) and a liquid (gasoline) to the combustion chamber in equal, homogenous proportions. 

It helps that gasoline is so volatile but it's density is significantly different than air so complete atomization of the fuel and homogenous mixing with air is difficult to achieve in every runner across the rpm range. 

I found Jay's painstaking efforts on the SOHC dang interesting.  I'm more concerned about balancing for engine longevity than I am about performance but I think it's all tied together.

[mike7570]

What can you guys tell me about photo of spark plugs below?
Shelby intake copy of RPM, Break in time plus about 6 1/4 mile passes.
428 stock eliminator motor - Autolite plugs, MSD, VP-110, 36 degrees, 89/90 jets, 1” open spacer, 850 vac.
I changed up to NGK plugs 90/91 jets and they look a little better. I’m seeing 2, 6 & 8 slightly lean?
Can’t touch intake but can change up spacer, timing and jets. I’m still experimenting with timing and jetting but would like to bring #8 around. Staggered jets?
Thanks, Mike

[XR7]

Hi Mike, I didn't think that intake was legal in Stock Eliminator. I thought only the 428 CJ iron intake and the C7 PI aluminum intake was all that could be used? They are always changing rules so maybe NHRA now accepts the Shelby lettered (Edelbrock RPM style ) intake? Curious if and when they changed that. I could be wrong, have been before LOL.

[mike7570]

Not sure what year, my manifold has Shelby name plate cast in manifold with no Edlebrock identification.  The Shelby name plate manifold comes with a cut down divider. For a ‘67 Shelby in stock eliminator a Holley #3418 850cfm is also legal.
I’m surprised at the jet sizes I’m running and it appears I can go larger although my experience with FE’s is leaner is usually a little quicker.

NHRA Notes:
Cylinder Head Castings
1 - C7AE-A, C6AE-A, R, C8OE-N,(F5WE-A Stock Only)
2 – Carb sizes 1.750 X 1.750/1.562 X 1.562 or 1.686 X 1.686/1.375 X 1.437
3 – Alternate intake manifolds C7AE-C, C7AE-F and Shelby (nameplate cast in manifold)
4 – Alternate intake manifolds C7AE-H and C5AE-E Shelby nameplate cast in
5 – Carb number C5AF-BC  1.686 X 1.686/1.313 X 1.375 or BU & BT  1.686 X 1.686/1.375 X 1.437