Big difference in an 4.500" bore engine and a 4.310" bore engine. A single plane is better suited for a Big Bore engine due to the amount of cylinder fill area you have initially. The Dart intake is a good piece. It is currently getting "tweaked" by an intake designer and I look for Dart to introduce an next generation in the up coming months.

Chris

I have both victor jr's now. I'm still on the fence as to putting the motors on a dyno simply because of cost. I am very curious as to what horse these motors will make. The set up seems to be a solid one without being overly aggressive.
I have also heard that the larger bore is FAR better suited to airflow as the 454 or 468 even, still crowds the valves. So in the end, maybe the difference will not be all that significant...

Brian,
The following dyno chart will provide some interesting information regarding your decision as to the correct intake manifold for your 468 cid engine. The test was performed on the same engine as yours (468 CID Chevy big block/hyd flat tappet), the only changes from test to test was a swap of the RPM Air Gap manifold for the Victor Jr manifold, both with 1” spacers, for a basis of manifold comparison only. There were no other tuning or component changes. It is “apples to apples” with no other variables to be considered. The test engine is nearly identical to yours, however what differences there are may affect the total HP/Torque figures, it will be a clear indicator of what manifold will operate the best in your particular application and required rpm range. Your cam has slightly more lift and duration and a wider LSA than the test cam (236*/246* .553/. 571 on 114* LSA vs. 230*/236* .552/. 555 on 110* LSA). Keep in mind these will move your engines HP/Torque peaks higher in the rpm range than the test engine.
The results.
The Air Gap produces significantly more torque (nearly 30 lbs/ft @ 3900 rpm) and HP (20 hp @ 4200 rpm) throughout the entire rpm range until 5000 rpm. The Victor Jr does not surpass the Air Gap in either category until above 5400 rpm. The Victor Jr does make 6.3 more hp and 8.8 lbs/ft torque @ 5700 rpm.
This test would indicate that unless you are propped for 6000+ rpm @ WOT, and do the majority of your running @ 4500–5700 rpm, the Air Gap would be the clear choice for the 468 CID. The full test and build sheet are at this link.
http://www.carcraft.com/techarticles/116_0109_big/
Bob

Good read Bob, as I stated in No.8 post on this thread. . .Airgap.

Chris Straub
Stef's Performance

Bob and Chris,

I should have known better...

I'd still like to dyno them because of all the reasons Bob gave me...

Brian,
It depends on what type of running you want to do, RPM range you run, and how much pain you want to put your wallet through. Like they said earlier, dual plane works good under 5000 RPM, but start to lose some power as they climb. The single planes are made to produce power all the way to the uper RPM range around 9 grand. with a bigger motor, especially a 468, I'd go with the dual plane. You might sacrifice a little low end, but whoever wnats to run you will deffinantly get smoked!! Have fun!

Ran stock hi-rise dual plane manifold(Winters)with 1" spacer on a 468 with 9.6:1 compression.
Had Crane 731 cam,800 Holley,Stainless exhaust.
Engines ran out at 5,600rpm with 475HP
Went with port matched Victor Jr. and saw no increase on top.
Actually boat planed out easier with dual plane.
Had better torque on the bottom with dual plane manifold.
Mo money wasted.............:rolleyes:

Brian,
Hey we all have to learn, I over cammed my first hotrod. I am a nobody and a "Who" to most on this board. I work with engine builders only across the nation and the world. We make oil pans. But I get the "low down" from the top engine builders in the country, hell on most sundays 37 out of the 43 have our stuff on them. So when I say top, I mean the professionals. Since I have to live with my customers, I have to have the right answer or they loose trust in you.

Chris
Stef's Performance

I'm running Brodix single planes w/1050 Dominators. Valves are .225/.188. Runs good, idles good:cool: :cool:

Very impressive article on the Air-Gap vs. a race prep single plane. I would like to see an extrude honed AirGap used. Best of both worlds.