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What’s the difference between the 6.2 vs 6.4 short block for forced induction?

7422 Views 9 Replies 5 Participants Last post by  Xylander
It looks like both have cast pistons and rods. Procharger says their supercharger is designed for the 392 and the latest design does over 200hp putting it in HC territory and the SP already has the 3.09 LSD rear.

What am I missing?
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It can DO over 200hp, but it won't on the 392 unless you swap the pistons. The max load the 392 can take is 5-6psi. 5 being relatively safe and 6 being in the hard yellow danger zone. A P1SC or P1X head unit won't make 200hp on 5psi. You'd need around 7-9psi for that (7 if you find a way to greatly increase the charge air cooling by way of something like a race intercooler) and 9psi will grenade the stock 392. Keep in mind that ProCharger is not going to warranty your engine if it blows up. The general consensus is 5-6psi is in the safe range. Any higher and you're on your way to building a hand grenade.

Now, I used to own a shop that was a certified ProCharger and Diablosport installer and they were one of my sponsors. I know the ProChargers very well. One thing the marketing stuff you're reading doesn't tell you is that if you do get 700 crank hp out of it, it only makes that figure at the extreme top end of your RPM band. ProCharger is similar to a turbo in that it makes boost in direct relation to the engine RPM (which is why ProChargers on Mustangs make so much more HP because they run at a lot higher RPM). Thus, the Hellcat makes most of its available power off-idle, where the ProCharger equipped 392 only makes that power between 5,500-6,100rpm. It offers very little gains below 3,000rpm in the case of the P1SC. The P1X makes gains closer to 2,000rpm. It's also a helluva lot more expensive.

In terms of engine design, the Hellcat has a lower compression rating and different pistons. The 392 has shallow ring lands which can't inherently take much boost. Heck, they have problems with the same issue on larger cams. Another difference is in the rod and crankshaft design in how they allow for crank journal overlapping. This greatly increases the inherent strength of the internals.

And another thing you're missing is that the stock 8HP70 transmission in the 392 is only rated for around 590lb.ft. of torque and something like 650hp. Anything beyond a very minor boost increase is going to overmatch the transmission. Some people swear the 8HP70 can take it, but I can also point out more than a few dead transmissions that failed with a P1SC ProCharger. If you have to swap the transmission, you're going to easily double the price of a build.
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I had a supercharged 2011 Challenger srt8 with a Magnuson running 6 PSI. It ran fine and I had no issues at all, but don't dare go over 6 PSI. Nothing wrong with building your car at all, just ensure your tuner has serious street cred. Many of these shops have zero clue how to properly tune a Gen 3 Hemi and do not adjust the fueling to keep the engine from detonation.
Detonation is an issue, but the real problem is the 392's shallow ring land on the piston. Too much boost can force a ring land failure (piston goes up too high,and kablooey goes your entire engine). The RIGHT way to build it to swap the pistons and rods, upgrade the trans and do your FI. The ProCharger is a fine unit, but if you cut corners you're left with one of two things: 1) A low hp build with a blower that can flow 30% more, but isn't being allowed to in order to save the motor, or 2) You end up building something of questionable reliability. Option 1 is extremely expensive (around $20 grand all in), Option 2 only costs about $8,000 until something breaks... then add either $15,000 for a new engine or $10,000 for a transmission if one of them fails (not including labor).
Great post!

The P1-X upgrade is only +$200 add to the standard HO kit.

At 6psi what does the HP gain drop to?
Isn’t the supercharger always on? What happens at 2-3000rpm vs lower rates?
I haven't dyno'd many 392s, but on a Mustang @ 9psi, they make around 680whp. At 6psi they do in the ballpark of 550whp.

Yes, the supercharger is always on, but it's a belt driven unit. Below 3,000rpm, it's only making 10-15% of its max horsepower. The power of the unit (boost) isn't set in the tune. It's set via pulley selection and the tune is configured for the fuel delivery and timing settings for the chosen pulley.

If the P1X is only a $200 upgrade, that's a good deal. I've been out of the game for 4-5 years and they were much more expensive back then. IMO, the P1X is the way to go as it gives more boost at lower RPM.

One last thing, some folks love the ProCharger sound, others hate it. In the video below, this was my Mustang that was later boosted to over 17psi. This is very early on its in build with just a P1SC that dyno'd a shade over 700whp. The ProCharger with the straight cut gears (loud version on this car) makes around 90 decibels at idle... which is louder than most cars at WOT. The helical gears are about 30% quieter:

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