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I beleive its due the tuning, better rear end, and more efficient use of the accessories (a/c, alternator, etc.) on the SRT. I also think the 6.1 makes a little better than 425hp, maybe more like 450hp.
 

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Traditionaly manual transmission cars have less drivetrain loss then automatic cars. This is due to a few things. 1) The manual car will fully engage the clutch while the automatic cars have a torque converter that slips-(not directly connected) 2) The additional weight of the converter saps up some power. Quite often an LX transmission has approx 19% loss and the new 6speed manual should have approx. 15% loss.
 

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I believe its due the tuning, better rear end, and more efficient use of the accessories (a/c, alternator, etc.) on the SRT. I also think the 6.1 makes a little better than 425hp, maybe more like 450hp.
Wouldn't be the 1st time a car company underrated the power of their engines.:bigthumb:
The IRS on SVT vehicles from 99 to 04 seemed to work well for open track racing but did not hold up to the rigors of drag racing. Wheel hop was an issue along with lots of broke half shafts when sticky tires and power adders were used. Seems to me even the so called heavy duty after market half shafts were failing at the CV joints just like the stock pieces. Numerous companies sold braces along with a lot of other junk that was supposed to fix all the problems but at the end of the day it was still a light weight aluminum axle set up. Most serious street/drag racers were ditching the IRS in favor of the Ford 8.8 live axle (SRA suspension), that bolted right up. I'm not sure if MOPAR offers a live axle for the Challenger, Charger, C300 & Magnum platform.
Also be aware of chassis flex that can occur with unibody vehicles. If it is a problem I'm sure the aftermarket will come up with a solution.
Just trying to give you all a heads up.
 

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So far the LX chassis has been able to handle 500-550whp without much issue. But I think this is due to a couple limiting factors. We havent had a transbrake option, and we are limited on what drag radial can be easily run. -- Therefore when these cars have lanuched, it has been rather gentle vs a hard 4000+rpm slam of a transbrake or manual transmission.

Sure we have a car here that consistantly pulls 1.5s 60ft time. But once people get a better hooking tire, and a transbrake/or manual transmission - then we will really see what parts break. The driveshafts are tiny, I cant believe they have held up so long. So far we have not had even one broken driveshaft though. Axles are a proven weak link, we recommend they be replaced with anyone running over 430whp and drag radials.
 

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So far the LX chassis has been able to handle 500-550whp without much issue. But I think this is due to a couple limiting factors. We havent had a transbrake option, and we are limited on what drag radial can be easily run. -- Therefore when these cars have lanuched, it has been rather gentle vs a hard 4000+rpm slam of a transbrake or manual transmission.

Sure we have a car here that consistantly pulls 1.5s 60ft time. But once people get a better hooking tire, and a transbrake/or manual transmission - then we will really see what parts break. The driveshafts are tiny, I cant believe they have held up so long. So far we have not had even one broken driveshaft though. Axles are a proven weak link, we recommend they be replaced with anyone running over 430whp and drag radials.
500 to 550 RWHP is just the beginning for these cars. I agree that so far drive line shock and stress haven't been fully realized on this platform yet for the reasons stated. The weak links will show themselves as the power levels increase, stickier tires are used and launches become harder. 4100 lbs is a lot of mass to get moving. While on the subject of hard launches Tremec, Lakewood, Hayes or somebody needs to come up with a safety bell housing that is capable of containing a clutch explosion and will integrate with the T56 transmission. I haven't followed the T56 product line closely so maybe that has already occurred.
 

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Are the internals forged in these engines?

Any guess as to what they will hold on a stock bottom end or where the weak points are that need to be built for near 800 rwhp?
NEW factory 425HP 6.1 HEMI SRT8

This doesn't answer your question directly but is interesting none the less. Below are some specs I found and copied into a Word file. I've had this for a while and don't recall where I got it from but I would contend the bullet points are accurate or I never would have copied the info. In addition I've read in a number of places the pistons are indeed hypereutectic. Probably due to the fact they do not expand and contract like forged aluminum thus providing better emissions regardless of engine temperatures (when cold).
Some good engineering has gone into this engine.

The SRT version produces another 85 horsepower and 30 lb-ft of torque than the 5.7 liter Hemi, and only some of that comes from the extra .4 liters of displacement. The Hemi produces more power per liter than any past Chrysler V8, including the 1966 Street Hemi, though with the technology available today, that's not surprising. Changes to the 5.7 include:
· The basic, deep-skirted engine block structure was redesigned with reinforced bulkheads to handle higher loads.
· To get more air in and out of the cylinders, SRT engineers bored out the diameter of each cylinder by approximately 3.5 millimeters in order to increase the total displacement from 5.7 liters to 6.1 liters.
· Cylinders are honed with torque plates to ensure a truer bore, to reduce friction and increase power.
· Oil squirters, aimed at the underside of each piston, are added to aid piston cooling for engine durability.
· A special oil pump pressure relief valve is added to accommodate the squirter oil flow.
· The oil pan and windage tray are modified to manage oil return to the pan sump at high engine speeds and improve power.
· Larger-diameter, flat-top pistons with high-load capability are specified to handle the SRT 6.1-liter HEMI’s compression ratio, which was increased to 10.3:1 from 9.6:1.
· Connecting rods are redesigned and make use of higher-strength powder metal material.
· New floating piston pins are introduced to handle higher loads.
· The SRT 6.1-liter HEMI’s crankshaft is forged from micro-alloy steel and rotates in tri-metal main bearings for high-load capability. The crankshaft damper is retuned for higher engine speeds.
· The SRT 6.1-liter HEMI features cylinder head ports designed with larger cross-sectional area. This allows 11 percent higher flow in the intake ports, and 13 percent higher flow in the exhaust ports.
· A billet steel, high-strength camshaft features more overlap and lift for better performance.
· Intake valves feature hollow stems and 2 mm larger heads compared to the 5.7L engine, allowing more air flow. The hollow exhaust valve stems are filled with sodium to dissipate heat efficiently.
· Premium valve springs with external dampers enhance the SRT 6.1-liter HEMI’s valvetrain and enable higher engine speed operation to 6,400 rpm. The valvetrain system enhancements allow the peak output engine speed to increase to 6,000 rpm from 5,000 rpm — a 20 percent increase.
· Engine breathing is improved with specially designed intake and exhaust manifolds. The cast aluminum intake manifold is designed with shorter, larger-diameter and tapered runners for high-speed tuning. Internal runners are core-dipped to smooth the runner finish and improve air flow.
· Fuel injector flow capacity is also increased by 14 percent over the 5.7-liter engine.
· Electronic throttle control is shared with the 5.7-liter HEMI, but breathes through a revised high-flow air cleaner box outfitted with a tuned resonator delivering a deep performance sound character (and good for an extra eight horsepower).
· Exhaust headers on the SRT 6.1-liter HEMI are individual tubes encased in a stainless steel shell. Exhaust runners allow increased gas flow while maintaining fast catalyst light-off, while adding 12 horsepower over the 5.7-liter engine’s cast manifolds.
· To control the combustion process, SRT engineers fine-tuned the engine management system using dual knock sensors with premium fuel.

ENGINE: 6.1-LITER, HEMI® V-8Displacement
370 cu. in. (6059 cu. cm)
Bore x Stroke
4.06 x 3.58 (103.0 x 90.9)
Compression Ratio
10.3:1
Power (estimated SAE net)
425 bhp (318 kW) @ 6200 rpm, (69.8 bhp/L)
Torque (estimated SAE Net)
420 lb.-ft. (310 N•m) @ 4800 rpm
Max. Engine Speed
6400 rpm (electronically limited)
Fuel Requirement
91 octane (R+M)/2 recommended (premium)
Oil Capacity
7 qt. (6.6L)
 

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Are the internals forged in these engines?

Any guess as to what they will hold on a stock bottom end or where the weak points are that need to be built for near 800 rwhp?

Only the crank is forged. The pistons and rods are the weak point for Forced Induction or NX. But that being said, if one wants to upgrade pistons and rods to forged parts to handle increased boost or nx, then it is recommeded that the crank be replaced as well because there are much stronger forged units available.


For 800whp you will need:
Forged pistons, rods and crank. - since this has to be done, it makes since to increase engine size to 392 or 426ci.
Ported Heads with larger valves.
Head studs.
Upgraded cam and push rods
Ported intake manifold.
90mm Throttle Body.
Underdrive Pulley.
Upgraded fuel injectors and boost-a-pump.
Headers, highflow cats, and catback exhaust.
Cold Air Intake-CAI.
Diablo Sport Predator programmer.

All of the above is a very common package we create weekly for customers. It will make 500-520whp on pump gas and can be daily driven.

To make additional power, will require a power adder of some sort. Ie. Supercharger,Turbocharger, or NX.

At 9si boost -NON Intercooled-, pump gas, daily driver: Our 426 will make 630-660whp

Adding an intercooler: 10-30 more whp.

Increasing boost: I would expect that 13-17psi would be needed to surpass 800whp. Boost needed will depend on how efficient the supercharger/turbocharger is. - There are many variables to consider, and I cant write 3 pages on here. lol.

Just a reminder: We sell all of the above componets and can create your dream machine.

Tim C
 

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Are the internals forged in these engines?

Any guess as to what they will hold on a stock bottom end or where the weak points are that need to be built for near 800 rwhp?
Iceman to give you another example of the modifications needed to get the kind of power you are asking about. Hennessey Performance Engineering has performed the following to a 2008 Challenger they call the SRT700 Turbo. Of course the drive line will need to be modified to withstand that kind of power along with the suspension upgrades necessary to get all that power to the ground.

SRT700 Turbo - 426 CID Engine Upgrade

Power:
  • 725 hp @ 5,200 rpm
  • 750 lb-ft @ 4,000 rpm
Estimated Performance:
  • 0 - 60 mph: 3.5 sec. *
  • 1/4 mile: 11.3 sec. @ 126 mph *
  • Top Speed: 190 mph
* with Drag Radial Tire Upgrade

Includes:
  • 426 Cubic Inch Displacement Stroker Motor
  • 9.0:1 Compression Forged Aluminum Pistons
  • Forged Steel Connecting Rods
  • 426 Stroker Crankshaft
  • Balanced Rotating Assembly
  • High Flow Cylinder Heads
  • Polished Intake Manifold
  • Single 67 mm Turbocharger
  • Stainless Steel Turbo Y-Pipe
  • Single 44 mm Wastegate
  • Stainless Steel Dual 3 in. Exhaust System with Polished Stainless Steel Exhaust Tips
  • Front Mounted Air-to-Air Intercooler
  • 3.5 in. Polished Inlet Tube with Blow-Off Valve
  • Upgraded Fuel Injectors
  • Upgraded Engine Management System
  • 180 degree thermostat upgrade
  • All necessary gaskets and fluids
  • Professional Installation
  • Chassis Dyno Testing
  • Road Testing (up to 100 miles)
  • One year limited warranty
 

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How much was hennessy asking for a package like that. I bet its as expensive as the car itself lol

Iceman to give you another example of the modifications needed to get the kind of power you are asking about. Hennessey Performance Engineering has performed the following to a 2008 Challenger they call the SRT700 Turbo. Of course the drive line will need to be modified to withstand that kind of power along with the suspension upgrades necessary to get all that power to the ground.

SRT700 Turbo - 426 CID Engine Upgrade

Power:
  • 725 hp @ 5,200 rpm
  • 750 lb-ft @ 4,000 rpm
Estimated Performance:
  • 0 - 60 mph: 3.5 sec. *
  • 1/4 mile: 11.3 sec. @ 126 mph *
  • Top Speed: 190 mph
* with Drag Radial Tire Upgrade

Includes:
  • 426 Cubic Inch Displacement Stroker Motor
  • 9.0:1 Compression Forged Aluminum Pistons
  • Forged Steel Connecting Rods
  • 426 Stroker Crankshaft
  • Balanced Rotating Assembly
  • High Flow Cylinder Heads
  • Polished Intake Manifold
  • Single 67 mm Turbocharger
  • Stainless Steel Turbo Y-Pipe
  • Single 44 mm Wastegate
  • Stainless Steel Dual 3 in. Exhaust System with Polished Stainless Steel Exhaust Tips
  • Front Mounted Air-to-Air Intercooler
  • 3.5 in. Polished Inlet Tube with Blow-Off Valve
  • Upgraded Fuel Injectors
  • Upgraded Engine Management System
  • 180 degree thermostat upgrade
  • All necessary gaskets and fluids
  • Professional Installation
  • Chassis Dyno Testing
  • Road Testing (up to 100 miles)
  • One year limited warranty
 

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Very interestinf stuff - thanks guys. I don't know that I'll open the engine up right away but it's good to know what I'll need to look at. I had hoped the pistons and rods would be forged so i could bolt on more power like the GT500.

No such luck but I still want one of these :)
 

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How much was hennessy asking for a package like that. I bet its as expensive as the car itself lol
I don't know what the price is but, if it has his name on it you can bet it will be expensive. I only used the Hennessey guide as a credible example of what is necessary to get to the kind of power levels Iceman was asking about. For the DIY gear-heads there will be numerous routes to take to dial the power numbers up and not come anywhere near the cost of a Hennessey built vehicle.
 

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I don't know what the price is but, if it has his name on it you can bet it will be expensive. I only used the Hennessey guide as a credible example of what is necessary to get to the kind of power levels Iceman was asking about. For the DIY gear-heads there will be numerous routes to take to dial the power numbers up and not come anywhere near the cost of a Hennessey built vehicle.
yea i know hennessy is expensive, but i hear he does good work when he isnt scamming people lol.

I personally will do the work myself, and save a lot of money doing so. I was thinking of going with a 426 stroker, and a positive displacement blower. I dont go to the track to much, i just want a very powerful yet streetable car. And i think the positive displacement blower is the best route for that.
 

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Very interestinf stuff - thanks guys. I don't know that I'll open the engine up right away but it's good to know what I'll need to look at. I had hoped the pistons and rods would be forged so i could bolt on more power like the GT500.

No such luck but I still want one of these :)
Yea, i wish dodge would have thought ahead and put forged internals into these engines. Must not have been very practical in their minds since they were not putting any type of forced induction on the car. Id like to see a blower upgrade of some sort from chrysler with a warranty option. That would be ideal.
 

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Before I came to PPP, I read all the magazines and Loved Hennessy. The Vipers they created were amazing. Then I came to work at PPP and saw a Jeep SRT8 SRT600 Hennessy package here getting work done. When I asked what we were doing , I found out that while the Customer bought the $28,000 package from Hennessy that should have included Forged pistons and rods, well it did not. Also there were metal bits in the oil pan from where they drilled for the oil return line and never cleaned it out. there were bare, stripped wires, it smoked heavly due to an incorrectly designed oil hose from the turbo and it was never tuned. The customer, after fighting with Hennessy for months, decided to take it here, where we put in a 426 storker and a new turbo. WOW- thats one heck of a run on sentence.

I have taken approx. 4 calls in the last 5 months from previous Hennessy customers who need their vehicle worked on / or rebuilt. I still love their Viper builds, but getting dissapointed in the things I hear.

--- Note. Just my opinion- without factual data to support it.. Dont try to sue me John. LOL
 
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