Magnum VS Hemi
Gen 3 5.7 Hemi heads flow 261 cfm at .500"
Maybe for the 03-08 5.7 head (the baby of the four OEM heads), but a Magnum head couldnt compare to any of the other 3 heads.
Ranges of 320-340 cfm for the Eagle, 6.1 and Apache are pretty hard to compete with, without porting. Even Dr. Js Airwolf 220 CNC ported heads dont make the cut.
The stock intake is not to blame, its the ignition. Replace the champion plugs gapped at .035 and they will pull well past 4500.
I find it hard to believe that plug gap would affect the RPM potential of a motor much. Maybe a couple hundred RPM, but a 1000 RPM?
Also, you cant expect an engine with a .439 lift 114 deg center cam to pull past 5000 but if you swap out the cam with say .550 on 112 or 110 then it should pull up to 6000.
Doubt it would pull that high with a kegger intake (shortened runners or not), but I never said I was blaming the lack of higher RPM potential on the intake exclusively. My focus on the intake is really only because it is the only part not available. There are plenty of cams, and heads, but nobody that I know of makes a dedicated EFI intake (meaning not a converted carb intake) for the Magnum. Im not saying a converted carb intake doesnt work, but a dedicated EFI intake is just something that has captured my imagination.
The beer keg manifold has over 16" runners. Remember when John Lingenfelter was building 180 + mph vetts and camaros? His signature manifolds were 15-16" runners. Those might have been GM mills but not one you would want to screw with in a small block Dart.
Info I have found says the 6.1 intake is about 3 inches shorter than the kegger. The LS1 is about 2 inches shorter than that. The later GM LT1 intake is supposed to be about 6-7 long in the runner, about the same as the more recent GM RamJet intake. Based on that, I am speculating that shorter runners would be useful.
Also, just a guess, but I would bet the kegger intake runners are pretty small in volume. Even though the 6.1 intake is only 2 shorter, I bet it kills it in volume. So, I am guessing, making the runner shorter would help with the lack of volume.
Lastly, the Allpar article where they flowed a bunch of Magnum intakes showed the stock kegger intake flowing about 180 cfm, and a modded one only flowing 10 cfm more. 180 cfm is good for maybe 340 hp based on one of the calculator I found (one said 180 was only good for 260 hp), but I bet that is the extreme and 300 hp is about the best you would see in the real world. And virtually everything I have read says the modded kegger help some in the middle of the RPM band, but doesnt help much on the top.
Longer runners make for more than atmospheric pressure at the port ie a small supercharger.
Not at high RPMs where they starve the engine for air. I'm sure you know all this but, runner length is tuned to a certain RPM range and outside of that it hurts it. Long runners are great for low RPM and for making torque, but not high RPM or horsepower. Short runners work well for higher RPM hp, but dont make as much low end torque. Its a trade for sure, but if you dont need the low RPM torque because you arent trying to get a 4500 lb truck moving, and you have the RPM potential to use a deeper gear to make up for the loss of low end torque, I think it makes for a more enjoyable motor (within reason).
Dont know about you, but I dont typically take my V8 cars in the 6K RPM range, more power and torque at say 4800-5200.
Im not looking rev it past 6K, but it would be nice if it pulled to some RPM close to that (there is a difference between rev-ing to an RPM and pulling to an RPM).
In their apps, it was unnecessary. The vast majority of trucks did not have enough gear to have more cam- that's why Ford, Chevy, and the Hemi trucks didn't make them look horrendous stock.
No argument. Not wishing they had build a car version for a truck, wishing the past had worked out different and there had been a RWD Mopar that needed a good performing V8, in the later 90s.