Dual Plane Intake

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   Looking at the engines I have ran on the dyno, I think I can say that the Air Gap intake has it on the performer and R4B. 
I do not have back to back testing but the average power seems to better with the Air Gap. 

Looking at a 401 and the last 390, 401 with Air Gap, 390 R4B, the 401 the considerable more power throughout the curve with the same cam. The 401 had Edelbrock heads moving similar to the iron heads on the 390 and about .5 more compression plus the extra stroke of course but I thought the 390 would have made closer to the 500 ft /lb TQ mark with the same cam the 401 made 520 ft/lbs with. 

The dyno sheets show the 401 and 390 results

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jcisworthy Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/23/2009 Location: North Carolina Status: Offline Points: 2805	Post Options Post Reply Quote jcisworthy Report Post Thanks(2) Quote Reply Topic: Dual Plane Intake Posted: Jul/07/2018 at 6:50am
	Looking at the engines I have ran on the dyno, I think I can say that the Air Gap intake has it on the performer and R4B. I do not have back to back testing but the average power seems to better with the Air Gap. Looking at a 401 and the last 390, 401 with Air Gap, 390 R4B, the 401 the considerable more power throughout the curve with the same cam. The 401 had Edelbrock heads moving similar to the iron heads on the 390 and about .5 more compression plus the extra stroke of course but I thought the 390 would have made closer to the 500 ft /lb TQ mark with the same cam the 401 made 520 ft/lbs with. The dyno sheets show the 401 and 390 results
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billd Members Profile Send Private Message Find Members Posts Add to Buddy List Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894	Post Options Post Reply Quote billd Report Post Thanks(1) Quote Reply Posted: Jul/07/2018 at 8:44am
	Isn't it hard to compare unless it's the same engine with only an intake swap? I mean - different carburetors - even if the same, won't BE the same due to slight differences in fuel bowl levels, and other factors, different engines responding differently to timing due to stroke and rod differences (14 degrees after TDC is a generic rule for peak combustion pressures, which means a slightly different stroke and slightly different rod length will matter as would a degree or two of timing) I saw a test on a MOPAR where it was the same engine and the results flew in the face of the same sort of test done with a SBC - where the dual-quad intake actually did a little bit better (meaning about 3 HP and about 5 higher on torque) vs. a good Edelbrock single bbl intake. I saw the same sort of test done earlier on a Chevy engine and the torker did better, but on this mopar engine, the Offy dual quad did better. I can see "getting close" in comparing, but really, is it fair to say "this intake does better, period, unless it's a swap on the exact same engine? If one could say "this intake always does better" then the others wouldn't sell and yet others use them for reasons. No offense, but the scientist in me (yeah, I did science stuff waaay back) says it's not a fair comparison using different engines even if "built the same" as they are never truly the same.
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purple72Gremlin Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Charter Member Joined: Jul/01/2007 Location: Illinois Status: Offline Points: 16615	Post Options Post Reply Quote purple72Gremlin Report Post Thanks(1) Quote Reply Posted: Jul/07/2018 at 9:18am
	Only way its a fair comparison is everything has to be the same.. except the intake.. Guessing doesnt cut it for me. However, had one gentleman tell me he compared the airgap and torker. He ran the intakes, same day, same car on a chassis dyno....no changes other than the intakes...the torker put out about 6-10 more HP at the rear wheels. However, he did say the air gap was smoother....ymmv.

Red Devil Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/10/2007 Location: Canada Status: Offline Points: 1743	Post Options Post Reply Quote Red Devil Report Post Thanks(1) Quote Reply Posted: Jul/07/2018 at 11:03am
	I assume jcisworthy is saying the trend shows better overall average power with the RPM AirGap in his dyno tests of a few engines using dual-plane intakes and the same small-cam. I respect that opinion as a general observation since he has actually done the work in building and dyno testing the engines. I also find it interesting since the AirGap often does poorly on the flow bench. People choose intakes for many reasons: nostalgia of an R4B, cool looks of a dual-quad, cold-weather performance of a Performer, proven all-around versatility and top-end of a Torker, stock for sake of stock use, latest design for sake of wanting the latest technology, etc. I appreciate the work jcisworthy has done and the details and opinions he shares. Ultimately, up to the reader to analyse the results and decide for themselves. ... but that's just my 2 cents, which doesn't get you much nowadays

jcisworthy Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/23/2009 Location: North Carolina Status: Offline Points: 2805	Post Options Post Reply Quote jcisworthy Report Post Thanks(1) Quote Reply Posted: Jul/07/2018 at 1:56pm
	Only an educated guess based on running different combinations on the dyno. I could be totally wrong. This is what figured may account for the 390 not making as much torque as I expected but it is in no way conclusive because of the combinations, although close, are not the same. The Air Gap, performer, and the R4B hurt the heads similarly on the flow bench so as far as that goes, I would think they would make about the same power Maybe the half point of compression and extra stroke makes more of a difference in the zone it is in more so than if it was 11 to 11.5 compression with more stroke for example. I just never expected a 60 ft/lb of torque difference
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jpnjim Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Nov/25/2007 Location: New England Status: Offline Points: 2752	Post Options Post Reply Quote jpnjim Report Post Thanks(0) Quote Reply Posted: Jul/08/2018 at 9:42am
	Thanks for posting up John! (again!) I like this comparison a lot because there is very little dyno data out there that I could find on R4B's, and I'm interested in exactly where R4B's might fit with it's good sized runners, but it's ages old design. Since this is two different engines with the same cam, we have to make a few assumptions to directly compare the results. 1) the 390 (395?) is smaller than the 401 (406?) 406/395 = 1.03 correction factor. If I use a 1.03 correction factor it's not entirely fair since the slightly smaller 390 "see's" the small cam and intake as being larger (in comparison to it's cubic inches) than the 401 does. Meaning that small cam is bigger in a 390 than it is in a 401. ^so using a 1.03 correction factor on the 390 actually gives it a slight advantage here, but it is what it is. 2) Cylinder heads, worked over iron heads vs worked over(?) Eddy's. Since the head porter (John) said they are very similar I'll take him at his word and make that a wash power wise. 3) .5 compression increase. The aluminum head engine has .5:1 more compression than the iron head engine. The school of though I was taught years ago was the Aluminum heads disipate heat (energy) so much better than iron, that all things being equal, the aluminum head engine is at a disadvantage power wise. Since this comparison gives an extra .5 compression ration to the aluminum headed engine I will also consider that a wash. So, with less than perfect comparison, using a 1.03 correction factor on the 390 gets us a little closer to a perfect comparison. If you do that: Torque R4B vs Perf RPM 3000 RPM +29TQ 3100 RPM +33 3200 RPM +39 3300 RPM +40 3400 RPM +46 3500 RPM +45 3600 RPM +39 3700 RPM +40 3800 RPM +41 3900 RPM +38 4000 RPM +40 4100 RPM +34 4200 RPM +34 4300 RPM +38 4400 RPM +33 4500 RPM +26 4600 RPM +21 4700 RPM +24 4800 RPM +20 4900 RPM +19 5000 RPM +15 5100 RPM +8 5200 RPM -7 5300 RPM -10 5400 RPM -19 5500 RPM -18 ^this tells me that the Performer RPM makes more torque over the R4B until 5200RPM, when the R4B starts to pull ahead. This is slightly unfair to the 401/Performer RPM because the 401's drop could just be the 401 "running out of cam" at that point, and the 390 staying on power with the same cam for a few hundred more RPM's. 390's torque starts dropping sharply at the 5400 point vs the 401's drop at around 5100. Both engines had peak torque 3800 so a good guess is thats a function of the cam, and the later drop off is a function of the intake, but it's only a guess. ^thoughts? With this one test I'd personally lean towards the R4B giving up a chunk of mid range for a bit more on top, but really the test only scratches the surface here.
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jpnjim Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Nov/25/2007 Location: New England Status: Offline Points: 2752	Post Options Post Reply Quote jpnjim Report Post Thanks(0) Quote Reply Posted: Jul/08/2018 at 9:51am
	I thought about running the numbers using HP and not Torque, but since HP is also a function of RPM that would make the 390 (+1.03 correction factor) look even better at the top end after the 401 started to fade, torque curves are much flatter, and don't make a little bump at the top end seem like it can make up for a big canyon in the midrange the way looking at horsepower alone can.
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jcisworthy Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/23/2009 Location: North Carolina Status: Offline Points: 2805	Post Options Post Reply Quote jcisworthy Report Post Thanks(0) Quote Reply Posted: Jul/08/2018 at 11:07am
	Jim, my guess is the Ari Gap is good for 10-15 numbers mid range but only a guess right now I do have a 401 build coming up with an R4B and the same cam which will have similar compression to the 401 previously tested. That will be a much closer test although it will have ported iron heads instead of the Edelbrocks.
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Ken_Parkman Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jun/04/2009 Location: Ontario Status: Offline Points: 1814	Post Options Post Reply Quote Ken_Parkman Report Post Thanks(0) Quote Reply Posted: Jul/08/2018 at 10:38pm
	Fascinating data jcis - my thanks as well. Really good info; you've done a test I wanted to do. I agree with the conclusion on the air gap for a street car, but I've got a few qualifiers. Gotta say up front I don't really like the air gap. It confuses me a bit, why have the race type no manifold heat, yet put a really small csa that cannot make a lot of power? Is it street or race? It seems like that may have been optimizing it for the 360, not the 401. I've run them all on my street Rambler, and dynoed the air gap and torker - but not the same day Purple; however I tried to control the variables as much as possible. No question the air gap makes a terrific torque curve. Really good for scaring the wife when you roll into the throttle, but it's not actually any faster. That's why I always go back to a torker - it's faster and I'm a performance guy. Your data tells me that an air gap will feel better for the average guy who does want to scare the wife, but is not likely to go to the track. Those small csa runners really boost the mid range. But those same small runners are too small for a 401 much over 5200 rpm. The power flat lines too early - it's choked. It might help an auto with a mild converter cause the shift rpm drop is so much, but not so good with a stick or an auto with a race converter. The R4B data is real interesting, and to me shows it to be a better performance manifold. Makes sense with the bigger csa. You have 11 less inches, .5 less compression, and probably not as good a combustion chamber (dyno them with the same headers?) yet it made more power even with those limits. It's still gaining big time above 5000, not choked. Is the 5500 rpm the cam limit, (hydraulic?), or do you think it was a head csa limit? With the limits of the inches and compression the R4B shows well and a better power intake. On the 401 I'd bet you would have seen more power. Probably faster at the track with the R4B, but the butt dyno will like the air gap. A great test would be a R4B vs a Torker.

jcisworthy Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/23/2009 Location: North Carolina Status: Offline Points: 2805	Post Options Post Reply Quote jcisworthy Report Post Thanks(0) Quote Reply Posted: Jul/09/2018 at 3:42am
	Thanks for the input Ken. I used the same headers on both and it is a hydraulic flat tappet cam. The R4b does have a larger CSA compared to the Air Gap and the air through the intake on the flow bench is similar between the two. That is why I thought the 390 would make more power than it did. Maybe my expectations were too high for this combination. Not that i am disappointed in any with the power of the 390 for what it is. Without having all three intakes here. I want to say from memory that. I liked the shape of the Air Gap runners better than the R4B or Performer/ I would need the three in front of me again to confirm. I have an R4B and a Performer here now so I can check them out side by side better later. As far as the Torker goes, I am a Torker guy also.
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