Converter Recommendation

[71 Nova]

OK I’m looking for a converter recommendation for my Nova with its new engine. I’m going to install 408 SBC. Here’s the engine specs:

408ci Small Block Chevy
• GM 4 Bolt Main Block Race Prepped to 4.030″ Bore & 4.000″ Stroke
• 4.000″ Stroke 4340 Internally Balanced Steel Crankshaft
• 6.0″ Stroker H Beam 4340 Connecting Rods w/ARP 8740 Bolts
• Wiseco 13.5/1 Compression Pro Tru Series 2618 Nitrous Pistons
• Total Seal Plasma Moly Rings
• Dart Iron Eagle 230cc Heads w/49cc Combustion Chambers
• 2.080″ x 1.600″ S/Duty Stainless Steel Valves
• Rolled Radiused Valve-job w/ Bowl & Port Clean Up
• Manley 10° Titanium Retainers with Comp Cams #611-16 Lash Cap Style 10° Valve Locks
• Cometic Nitrous MLS Head Gaskets
• Lunati .691″ Lift 4/7 Swap Custom Roller Cam
• Comp Cams #818-16 ” Extreme Duty Vertical Bar Roller Lifters
• Roll Master Billet True Roller Timing Set w/Torrington Bearing
• Manley .080″ Wall Chrome Molly Push Rods
• 7/16″ Stud Ultra Series Stainless Steel 1.55 Roller Rockers
• AERC Professional Series 4150 Match Ported Aluminum Intake
• 850cfm Holley Pro Series Carb w/1″ Spacer
• Moroso 7qt. #20200 Oil Pan
• Mallory Comp 9000 Distributor w/Large Red Cap
• Moroso Crank Trigger Assembly

Here’s the power curve off the engine dyno:

RPM Torque Hp
4500 445 381
4600 462 404
4700 468 419
4800 474 433
4900 480 448
5000 492 468
5100 493 479
5200 499 494
5300 512 516
5400 517 532
5500 527 552
5600 538 574
5700 542 588
5800 548 605
5900 550 617
6000 550 628
6100 546 634
6200 542 640
6300 536 644
6400 529 645
6500 522 647
6600 517 650
6700 512 653
6800 505 654
6900 499 655
7000 491 654

Here’s the setup for my 1971 Nova

Weight = 3120 lbs, with driver 3330 lbs.
14 point roll cage
Turbo Hydro 350 Trans w/ heavy duty hardened internal parts (intermediate sprag)
3.5" steel driveshaft w/ heavy duty yokes and Spicer 1350 U-joints
10 bolt corporate 8.5" rear end w/ Auburn Posi and 4.10 Richmond gears
Moroso Drag Springs in front (214 lb/in)
Stock Multi-leaf rear springs
Competition Engineering 3 way adjustable drag shocks in front
Rancho 9000RS 10 way adjustable drag shocks in rear
Hoosier QuickTime Pro 27-10.50-15LT DOT legal drag slicks on 15x8" rims
Competition Engineering Slide-a-Link traction bars
---> Best time with my old 400HP 355 SBC, 150HP shot of N2O and a 2500 stall B&M converter: 11.41 @ 118 MPH, 1.669 60 ft.

I want to run this combo NA at first, then eventually step up to a max 200HP shot of N2O. So, what’s a good converter should I use??? I’m not opposed to changing gears or other items to optimize this setup. Let me know if I left anything out. Thanks for your consideration.

[Bob West]

Call ATI,Neal Chance,Coan, PTC, you get the idea

[jmarkaudio]

Well Bob, since Marty moderates this forum, not a bad place to ask.

I do have some questions, what are the rest of the cam specs and were you there at the dyno session? My reason for asking is that the #'s look off, peak torque happening later than they should for that engine and the torque to HP numbers don't match either. You take the torque and multiply it by the RPM, then divide it by 5252 to get your HP. This is why torque and HP always match at 5252 RPM. Here is a dyno sheet from my engine you can use to check the calculations.

[TubbedTruck67]

Call Marty Chance hell get you hooked up with what you need. A custom converter is the only way to go and Marty is an awesome guy to deal with. I couldnt be happier with my converter that I got from Marty.

[71 Nova]

Well Bob, since Marty moderates this forum, not a bad place to ask.

I do have some questions, what are the rest of the cam specs and were you there at the dyno session? My reason for asking is that the #'s look off, peak torque happening later than they should for that engine and the torque to HP numbers don't match either. You take the torque and multiply it by the RPM, then divide it by 5252 to get your HP. This is why torque and HP always match at 5252 RPM. Here is a dyno sheet from my engine you can use to check the calculations.

Sorry, I fouled up the numbers in the table (now corrected). Picked the wrong column when I copied the numbers. Good catch, thank you! No, I was not at the dyno session.

Here's the rest of the cam specs: Lunati PN 50199 solid roller cam with 4/7 swap
Lift at valve: Intake and exhaust (with 1.55 rocker arms) 0.691"
Duration at 0.050" lift: 276 deg (intake); 284 deg (exhaust)
Advertised duration: 309 deg (intake); 317 deg (exhaust)
Lobe Separation: 114 deg

[jmarkaudio]

N/A it should put you well into the 10's, have your cage heady to go with the 200 shot. LSA on the cam is wider than I would like to see even with a 200 shot unless you plan some street time. It would be nice to see HP #'s up to 7500, although it looks like the heads are done at 7000. For use with NOS I would look for a 9" about 5200 stall, for best ET N/A maybe an 8" at about 6000 stall, I might go a little more but your peak HP looks like it hits the downward path too soon at 7000. A glide would work better with that stroke, but try short shifting 1-2 about 6800 and 2-3 about 7300. Maybe Marty will catch this an tweak my stall #'s a little but they should be close.

[stroker1]

WOO,HOO!!! That's a lot of LSA for a big stroke motor with only possibly, one day, someday a 200 shot!! Just my 2 cents.

[Marty Chance]

i would recommend an 8" for the N/A and a 9" for the nitrous combo, call me and we can go over the specifics. Thanks Marty