A few things that really stand out for me on that test info from D & A Machine:

1. It appears they are comparing it to the GMPP single plane, not the Victor Jr.. While I have not seen back to back dyno tests, I have read several times that the Vic Jr. out performs the GMPP intake.

2. The camshafts in the test have an extraordinary amount of advance. One has a 102 ICL and the other a 103 ICL.. In addition, they are on a very tight ICL.. These cams are going to need a lot of compression and will have very poor vacuum and drivability characteristics. Not to mention very poor fuel economy.

3. The test engine is a short stroke, big bore custom combo that most likely no one who reads this will have. The camshaft that they created was custom designed for this odd ball combo. What they did is reminiscent of the old Boss 302 and 351 Cleveland engines from the 70s. The narrow lobe separation angle and early IVC are necessary to get the big, high volume port a/f charge moving and closes the intake valve quickly before the momentum stops. Without high compression there to help this combo out, I am afraid it might be a dog.

 

Dual plane and square port heads together, is a waste of time in my opinion.
The big square ports are happy with big cubes, or high rpm , and the dual plane wants completely the opposite

 

Tigger, the 409 they used in the Engine Masters was a .030 6.0 block w a 4" stroke according to the spec sheet in Popular Hotrodding Mag. Not sure where 409 came from, instead of the common 408. But it wasn't a odd ball big bore /short stroke deal. 224/228 at .050, 607 lift and a 108, installed +6. That's not that crazy a combo, is it? Mine is 108+4, 220/230. Idles great!

 

Have you run that combo in the 1/4 yet?

 

Went 12.15 at 112 in 90+* heat. I did a 1.86 60ft spinning. At the same time my converter was going away. The converter cracked and on the second pass it lost .2 and 2 mph. I limped it home. the 12.15 was with a 2100 stall w 3.42 rear gears. I have a shiny new EA stage 2 2004R and a 9.5" 2800 stall in it now. Im waiting for cooler weather to go back. I don't for see any issues going into the 11s with this combo. This car has road racing suspension, power everything including AC. I didn't build it for 1/4 mile duty, but would like an 11 sec time slip for the glove box, LOL.
It also pulls enough vacuum for my 4 piston, 13" 4 wheel disc brakes. The manufacturer says I need 16" of vacuum to function properly and they do. My cranking compression is 228, but runs good on pump 93 with 34* advance. The rest of the engine is bone stock GM crate LS3.

 

Sounds like your mind is made up with the heads. Go single plane since you are using nitrous and get a larger converter to flash the engine higher. A 4500 nitrous converter would do great. Will be right on motor but great on dope.

 

At 112 MPH, it should produce that no problem.

 

Yea, I think its there the next time out. I will be interested to see how much, if any, MPH I pick up just because of the trans issues. The car felt like it was in a bind on both of the passes I made. Im looking forward to seeing what happens.
Sorry OP, about the jack. But back to topic, Im a fan of the dual plane, I just wish one of the cam gurus on here would give it a go and see what happens with the right grind compared to the singles.

 

Lol its not gutless by any means. Its just not a torque MONSTER. It loves RPM. Not like My old lt1 383, That sob would shred tires in the bottom end of the gear, it was a torque monster, but had 0 top end.... But then again most races are won on the top end.

 

The BBC has benefited from the dual plane in street apps for years . That is the closes thing I can think of to compare the dual on the big heads. BBCs have huge head volume and need some help down low in smaller cube apps. Same thing for my situation, 376cid with heads that have a 260cc port. In my situation, a mild street build, I benefit from anything that will bolster low end grunt. This is why I built the package the way I did. Short duration, tight LSA, dual plane, 2 1/2" exhaust. It all works together really well. If I build an LS engine for my 68 Camaro in the future, it will be more purpose built for track duty. Big cubes, single plane, freer flowing exhaust, loose converter, and a cam designed to take advantage of the high RPM air flow of the LS3 heads. That being said , I disagree with you on the dual being a waste of time on the LS3 heads. It is just a means to a different end. Optimizing your setup for your intended use.

 

I don't get your comparison of his car to your car. Your car is lighter, daily drivability is a factor and shows in your camshaft pick. His cam is larger, smaller cubes, not worried about daily drivability so much as he wants to kill stangs. Your trying to use the dual plane as a crutch for a bad set-up IMO. You will end up compromising more than the gain also IMO. Really the original poster would have been better off staying cathedral but if he is going to go the high hp route you shouldn't half-way do it. You want those heads to shine put a single plane on it and bump the revs up.

 

IMO the dual plane will spank the single up to 6K, maybe higher because the cross section of the intake is HUGE. It isn't the twiggy dual plane that you see on the cat head engine. In the only tests Ive seen the LS3 dual made more power to the 6500rpm redline at every RPM. I guess the question the OP needs to answer is how hi is he going to spin it? Factor that with the OPs heavy car and smaller cubes and I see the dual winning over the single in the OPs app every time.
I think the point that everyone is missing is the LS3 heads love to move air, BUT the GMPP dual plane is a huge intake that can move as much air as the average 6.0 or 6.2 can swallow. You can gain torque down low and still move all the air that 6.0 will take with the dual. Is the OP going to spin his 6.0 to 7500 rpms? If so ,he may see a small advantage with the Vic Jr. Below that RPM Id bet my box of donuts on the dual.

 

Sorry been dealing with school.. Ok my max rpm will be 7000-7200rpms...I'll have my car on a 4 hr drive once a month...max spray i will be using is 150 shot, thinking on motor i will be just fine and the 150 will be just enough for when i need it...my previous setup had beaten a few stangs but now they want to spray me...how can i post pictures of the pistons stock valve reliefs so you all can see them....they're cut all the way to the edges of the pistons and pretty deep...how can i measure depth? Dial caliper??

 

stick a piece of clay in there to get a quick mold then cut it in half and measure with a caliper.

 

Yea, Im thinking the single will be the ticket with that high of a redline. What are you doing for a converter?

 

Ok on my way to shop to pick the heads up..had to get them checked and he milled them .020...will get some clay from him to measure and he also recommended doing a "valve drop" method to get ptv clearance, same method as EPS..ANOTHER thing, even though I'm saying 7k shifts, would i really need to shift it there? 6800-7k, might live a little longer there....really thank you guys for your help btw...

 

My converter is the 3600 built from Revmax..thinking going from 3.42 to maybe 3.73...have all parts already, it'll just be my time which i have no problem with..

 

With the 3600 stall/big ports/heavy vehicle weight/large cam its not going to leave hard. Need 4500 stall and 4.10's to keep the combo happy IMO.