Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, 708 Cam Stock Improvement.

ericj96

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Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, Cam Specs

I have been through a series of mods to my 1996 RT10 and would like to share some technical observations that may be helpful to those that would like to bring their late 90s Vipers up to gen 4-gen 5 straight line performance standards without sacrificing the cars drivability and idle characteristics. In short those that want their great looking collectable car to run like a gen four or gen five and almost pass for stock.

Heads:
Below is the dyno result from the installation of a set of Greg Good heads with roller rockers. The valves are 2.02/1.58 with 69.5 cc chambers after being milled. This yielded about a 10.2 to one mechanical compression ratio on my gen one.

Mod Set 1=Smooth Tubes & Filters, 3" borla exhaust from the manifold ****** back
Mod Set 2= Smooth Tubes & Filters, 3" Borla exhaust from the manifold ****** back, with Greg Good Heads and 1.7 Harland Sharp Rockers
Both data sets have stock throttle bodies, intake, cam and exhaust manifolds.

..........MOD1....MOD2
RPM T....HP.. ...T.....HP
1600 ................423 129
1800 ................424 145
2000 406 155 ..425 162
2200 412 173.. 424 178
2400 410 187.. 422 193
2600 417 206.. 441 218
2800 420 224.. 450 240
3000 420 240.. 452 258
3200 432 263.. 461 281
3400 442 286.. 479 310
3600 461 316.. 492 337
3800 460 333.. 491 355
4000 455 347.. 495 377
4200 455 364.. 502 401
4400 451 378.. 495 415
4600 438 384.. 490 429
4800 433 396.. 485 443
5000 420 401.. 469 446
5200 401 397.. 451 447
5400 383 394.. 439 451
5600 365 389.. 418 446
5800 335 370.. 390 431
6000 ................360 411

The entire torque curve lifted at least 12 ft pounds from 1500 rpm all the way out. Average increase in rotational force was about 9% at all points. Peak RW torque was up 40 ft lbs and peak horse power was up 50 RWHP. Peak HP and torque moved up 400 RPM. The heads flowed 285 cfm at 575 lift and 225 at 550 lift respectively. Point being have Greg Good rework your heads.



Picking the right cam:
I see it over and over on the net. People recommending these massive cams in our cars and then I go over and look at our long narrow runner manifold that wants to go completely out of resonance by 5750 RPM? There is an old adage in engine building that says “help your engine do what it wants to do and it will love you for it”. These massive long ****** engines with long runners want to build lots of mid range torque first and foremost. You can force the motor to peak in the 5500-6200 RPM range but you don’t pick much NET area under the curve for your efforts.

When I went to pick my cam I needed to know what was typical of the late 90s viper engines so I sent off some material to Comp Cams to be “cam doctored” these were the results:

Stock Gen I Viper Cam
Duration at .006” lift intake = 285 deg
Duration at .006” lift exhaust = 278 deg
Duration at .050” intake = 218 deg
Duration at .050” exhaust = 212 deg

Intake Center line = 117 deg
Angle between lobes = 114 deg
Intake lift at lobe = .308
Exhaust lift at lobe= .291
Intake closing event was 77 deg after bottom dead center----translates these cams do not have the exact same lift and close rates on the lobe if what comp cams is reading is correct.


708 Gen II Cam 1996 to 1999
Duration at .006” lift intake = 288 deg
Duration at .006” lift exhaust = 296 deg
Duration at .050” intake = 220 deg
Duration at .050” exhaust = 230 deg

Intake Center line = 117 deg
Angle between lobes = 114 deg
Intake lift at lobe = .321
Exhaust lift at lobe= .321


It has been my experience that on fixed timing (non direct injection) engines running pump gas you are asking for predetination problems when your cranking cylinder pressure gets into the 190s. Most tuners and the new Gen 4 and later engines are running without issue 10.2 to one compression so that’s the ratio I picked. The next question was what is the ideal intake valve closing point on the cam to give me my target cranking cylinder pressure of 182? The cranking pressure models suggest that 74 degrees after bottom dead center will yield a 182 psi cranking cylinder pressure.

Note that both the above listed factory cams have an intake duration of about 220 deg at .050” lift and a 117 intake center line. This late lobe center is the child of the long runners and the need for late valve closing as the column of incoming air is still trying to get into the cylinder long after the piston is on its way back up. This is black magic got to test it to get it right kind of research so I left the cam lobe centers in the same location Dodge did in the 90s before lobe centers were moved to keep the tree huggers happy in 2000.



Based on this I went looking for intake lobes and found the following:
Comp Cams Dodge Viper Camshaft Single pattern with 3051 lobes:
Duration at .006” lift intake = 274 deg
Duration at .050” intake = 220 deg

Duration at .200” intake = 134 deg
Intake Center line = 117 deg

Intake lift at lobe = .320
Intake closing event was 74 deg after bottom dead center

This is a faster than stock acting lobe that was developed for offshore marine racing engines that need to survive endless duty at high RPM and have excellent longevity characteristics. This cam has more area under the lift curve than the 708 but gave me a much higher average cranking cylinder pressure ranging from 181 to 189 psig depending on the cylinder bank and razor sharp throttle response. The engine now produces 550 RWT and I attribute some of this to increased area under the curve and high cylinder pressure created by a close to ideal intake valve closing point for the application.

I was so paranoid about losing my stock idle characteristics I just went with the same exhaust lobe as I did on the intake on a 114 lobe center angle. This profile made a wonderful gen one improvement cam. Its total specs are listed below.

Comp Cams Dodge Viper Camshaft Single pattern with 3051 lobes:
Duration at .006” lift intake = 274 deg
Duration at .006” lift exhaust = 274 deg
Duration at .050” intake = 220 deg
Duration at .050” exhaust = 220 deg
Intake Center line = 117 deg
Angle between lobes = 114 deg
Intake lift at lobe = .320
Exhaust lift at lobe= .320
Intake closing event was 74 deg after bottom dead center.

With the new 220 220 114 gen one replacement cam, Greg Good Heads, Harland Sharp Roller Rockers, 1.75 Tri Y headers, 3” Borla exhaust (bullet mufflers in the place of cats), 65mm throttle bodies, aluminum flywheel and ASP under drive pulley the car pulls the following rear wheel numbers on the Dynojet on a routine basis. The blue line on the attached dyno chart is with a completely cold motor and is not a reasonable representation of the motors characteristics in operation.

RPM…….. T....HP..
1600… 430…130
1800… 435…150
2000… 440…167
2200… 440…184
2400… 465…212
2600… 470…232
2800… 465…247
3000… 485…277
3200… 490…298
3400… 505…326
3600… 530…363
3800… 533…385
4000… 545…415
4200… 551…440
4400… 545…456
4600… 540…472
4800… 525…480
5000… 510…485
5200… 495…490
5400… 475…488
5600… 450…480
5800… 430…470
6000… 395…450


When the car pulled through tech at Atlanta Dragway or Atlanta Motor Speedway for Friday Night Drags the tech guys assumed it was a stock mid 90s viper with exhaust work. In the fall and spring with 600-700 DA a off idle launch and no burn out it turns the following if I don’t spin the tires, bog or miss a gear:

Eight Mile
60 ft…..1.85
330 ft… 4.94
1/8[SUP]th[/SUP]…. 7.45 at 99 mph


Quarter Mile
60 ft …..1.84
330 ft….4.92
1/8[SUP]th[/SUP]…..7.47 at 98 mph
1000….9.64
1/4[SUP]th[/SUP]….11.50 at 123 mph

This car runs with cars pulling better RWHP numbers because for a mild NA car its midrange is crushing. There is no “recovering from an up shift”.

If I had a gen two motor and wanted to mimic and replace the 708 but with more rotational force everywhere I would have used the same intake lobe but with the Comp Cam Magnum Marine exhaust lobe 3052 with the following specs:

Comp Cams Dodge Viper Camshaft Dual pattern with 3051/3052 lobes:
Duration at .006” lift intake = 274 deg
Duration at .006” lift exhaust = 284 deg
Duration at .050” intake = 220 deg
Duration at .050” exhaust = 230 deg

Duration at .200" intake =134 deg
Duration at .200" exhaust =142 deg
Intake Center line = 117 deg
Angle between lobes = 114 deg
Intake lift at lobe = .320
Exhaust lift at lobe= .320
Intake closing event was 74 deg after bottom dead center.



If you have not purchased a Viper Yet but are thinking about an early model I would keep in mind that 1996 was the first year of the easy to program OBD2 computer. I would also consider that 1999 was the last year for forged motors with a PCM that did not process any data from the second set of oxygen sensors. Do NOT use cheap Federal Mogul or Speed Pro roller lifters as you may have the chance to replace them twice because they would not pump up. ;-(

Hope some of this helps someone.
 

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CWhiteRun

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Re: Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, 708 Cam Stock Improvemen

Great post. If I read yoiur post correctly, you are say the 708 achieves more power than the after market CC?
 
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ericj96

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Re: Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, 708 Cam Stock Improvemen

No the CC 3051/3052 cam makes morepower than a 708 because its faster acting and produces more cylinder pressure.
 

EllowViper

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Re: Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, 708 Cam Stock Improvemen

Good stuff!! You made me go pull my cam card….let's see. Comp Cam custom blower grind # 3705 on intake and #3654 on exhaust.
Gross valve lift: .578/.593 (this is with TD 1.7RRs on a solid roller tappet with stock valves and CC springs) GG states max lift of .600 with stock valves
114 lobe sep
[email protected] .050 236/242
Dur @ .006 289/295

Intake opens @ 7 BTDC and close 49 ABDC
Exhaust opens @ 58 BBDC and closes 4 ATDC

111.0 intake centerline. And I have zero intake runner length on my blower manifold..other than what's in the head itself…and that opens right into a large open plenum with zero runners. Pow.
 
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ericj96

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Re: Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, 708 Cam Stock Improvemen

So you are about 75.5 ABDC IVC
What I your compression ratio and how much boost are you running?
 
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ericj96

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Re: Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, 708 Cam Stock Improvemen

That's a ton of pressure bet it pulls hard.
 

EllowViper

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Re: Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, 708 Cam Stock Improvemen

Broke the stock T-56 @ 13 PSI.
 

mad prof

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Re: Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, 708 Cam Stock Improvemen

Eric, I enjoyed very much reading your mod list on your 1996 RT 10. I have the same car and I am having very similar porting treatment in the cylinder heads by Greg Good. I am aiming at RWP 550 and similar levels of torque!

I need your wisdom in the following issues:

What type of exhaust are you using for achieving RWP 550? Do you use cats?

What do you do with the PCM? Have you flash it or use any other reprogramming system? How do you “tune” the PCM?

What type of throttle bodies do you use? 65m or 71m?

I really appreciate any help you could spare and your wisdom for my project will allow me to complete my ambition in making my Gen 1 engine realise its true potential without any long-term reliability issues.

Mad prof
 
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ericj96

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Re: Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, 708 Cam Stock Improvemen

Mad,

These were your statements:
"I am aiming at RWP 550 and similar levels of torque!
Answer ---My car only pulls about 490 RWHP when its 175 deg F. And about 500 RWHP when its **** cold so I am not anywhere close to your target of 550 rear wheel horse power if that's your goal. My car is about 565 fly wheel horse and 625 torque on a routine basis.

"What type of exhaust are you using for achieving (your output)? Do you use cats?"
Answer--I am running M&M Tri-Y 1.75 inch primary headers, no cats as they have been replaced with 3" stainless bullet mufflers and run of the mill Borla 3" cat back from there back. Mild deep rumble at idle and low load but at full throttle and 4,000+ RPM very loud but somehow not annoying. This set up will support higher horse power output than I have.

What do you do with the PCM? Have you flash it or use any other reprogramming system? How do you “tune” the PCM?
Answer-- my 1996 gen one is a OBD2 car and can have the air/fuel and timing curves changed with nothing more than an SCT tuner. My air fuel was corrected by an SCT controller. If your car is not a 1996 RT/10 gen one then you will need deeper help. Dan Cragin can help on 1992-1995 cars where SCT will not work.

"What type of throttle bodies do you use? 65m or 71m?"
Answer--- I run 65 MM and a 70 will just hurt you. The 65mm units flow 1200 cfm and if you take the time to put a large bore throttle body on the manifold after the manifold entry hole has been enlarged you will see that the incoming air has to make a sharp corner right after entry then this now turbulent air crashes into to humps coming down out of the top of the manifold that give additional material for the throttle linkage bolts. Point being larger throttle bodies have poor "line of sight into the intake and don't help much. I only went with 65 mm because gen one TBs have 56mm exit holes and that is a real problem. I ported the angular transition from square to round and ground the bolt humps flat with the top of the manifold. Much better line of sight and corner shape.

Frankly to hit 550 RWHP without forced induction you will need a very large cam like Greg Good normally specs out and maybe a gen three intake retrofit.


I cant help you hit 550 RWHP because when I went through my motor my goal was not power it was area under the curve and retaining idle characteristics so my mods are hard to pick up on.

Thanks

Eric
 
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mad prof

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Re: Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, 708 Cam Stock Improvemen

Thanks Eric for your answers. Most helpful. I guess getting a SCT is the trick for tuning the PCM. Where do you recommend getting hold of one? Do you need extra software to run the tunes?

Best wishes

Mad prof
 

Twister

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Re: Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, 708 Cam Stock Improvemen

11.5 @ 123 mph is respectable. Well done
 
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ericj96

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Re: Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, 708 Cam Stock Improvemen

I got mine from Injected Engineering in Metro Atlanta off I 75. The car obviously will require a dyno and a lap top.
 
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ericj96

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Re: Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, 708 Cam Stock Improvemen

Thanks twister thats a complement coming from you as your car is not a NA engine like mine. You guys with blowers know what fast is.
 

Twister

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Re: Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, 708 Cam Stock Improvemen

My 99 rt10 dynoed 450 rwhp with most bolt ons.

My 2003 srt dynoed 555 r whp with most bolt ons plus a 710 camshaft from roe racing. I never had a supercharged viper.

What I noticed with my 550 r whp gen 3 was that it was fast as ****. The area under the curb plus the sub 3300 pound race weight was simply killer. I'm sure yours is quite similar.
 

Twister

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Re: Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, 708 Cam Stock Improvemen

Curve not curb.
 
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ericj96

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Re: Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, 708 Cam Stock Improvemen

"My 2003 srt dynoed 555 r whp with most bolt ons plus a 710 camshaft from roe racing. I never had a supercharged viper.

What I noticed with my 550 r whp gen 3 was that it was fast as ****. The area under the curve plus the sub 3300 pound race weight was simply killer. I'm sure yours is quite similar."

I hear you, the old white girl has that fast as **** feeling. When I ran her for he first time after the work was done it was at Atlanta Motor Speedway for Friday night at the drags. Its a 1/8th mile run out of he pits with a pro tree and you just run eliminations no time slip. I noticed even before I ran my first timed run that I was frequently beating cars with roll cages. I took this as a good sign.

I am also learning to worry more about how much tire the guy is running more than the power they are pulling as long as the race is a quarter mile or less. I tend to fare well against guys running Nitto Drag radials, Pilot Sport Cup, Kumho Drag Radials etc but Hoosier wrinkle walls and the like are very bad news and I might as well pull off for Coffey for all the good it will do.
 
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Twister

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Re: Gen 4 & 5 Performance Well Hidden, Greg Good Heads Dyno, 708 Cam Stock Improvemen

Lol...so true
 

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