Conclusion
This swap to the Indy SR heads delivered a knockout punch beyond our expectations. Imagine the difference if we had tested them against a stock set of heads, either 906 or 452 castings. Moving to a more aggressive cam and a bigger carb would have surely given us a mid-10-second, pump-gas street car. Of course, for now, that's merely speculation. If you decide to use Indy heads on your B/RB, be sure to plan your combination wisely and don't try to put these heads on a low-compression motor and expect big gains.
Indy SR Heads Flow Chart
As tested at Ray Barton Racing Eengines SF-600 Flow Bench
Intake Flow
Lift
Intake | Stock | Stock With
Back-Cut | Ported | Ported With
Back-Cut | Port & Polish
W/Back-Cut | Port & Polish
With Back Cut and
MaxWedge style |
| .200 | 139 | 147 | 142 | 148 | 148 | 150 |
| .300 | 198 | 205 | 195 | 198 | 203 | 215 |
| .400 | 245 | 251 | 239 | 242 | 250 | 266 |
| .500 | 270 | 278 | 278 | 280 | 282 | 308 |
| .600 | 280 | 290 | 301 | 302 | 305 | 335 |
| .700 | 288 | 291 | 317 | 319 | 320 | 357 |
| .800 | 290 | 297 | 331 | 331 | 333 | 374 |
Exhaust Flow
| Lift | Stock | Ported | Ported & Polished |
| .200 | 112 | 112 | 112 |
| .300 | 149 | 150 | 151 |
| .400 | 192 | 192 | 195 |
| .500 | 214 | 213 | 215 |
| .600 | 232 | 235 | 239 |
| .700 | 245 | 247 | 252 |
| .800 | 253 | 257 | 260 |
Note: Indy sells the SRs with optional CNC super-modified porting with the Max Wedge-size intakes. It will save you many hours while returning flow numbers and performance equal to, or better than we achieved.
Chassis Dyno Results
Superflow SF840 SAE-corrected rear-wheel horsepower and torque tested at SLP Performance Parts & Engineering Center
| Baseline W/906 | Indy w/40 Timing | X Stream | Wilson Space |
| Max hp @ rpm | 366 at 5,600 | 433 at 5,600 | 433 at 5,600 | 433 at 5,600 |
| Max tq @ rpm | 427 at 4,200 | 457 at 4,200 | 460 at 4,200 | 465 at 5,600 |
| Avg hp @ 4,000-6,000 | 350 | 394 | 397 | 403 |
| Avg tq @ 4,000-6,000 | 367 | 410 | 414 | 421 |
Here's a before-and-after...
Here's a before-and-after look at the headers and exhaust. (A) The production-headed 440 headers from Hooker (1 7/8-inch into 3-inch collectors) and the muffler shop 3-inch, compression-bent exhaust would not fit the B-Body once the Indy heads were bolted on.
(B) The TTI headers (for Indy...
(B) The TTI headers (for Indy heads), feature 2- to 2 1/8-inch primary tubes into 3 1/2-inch collectors. The TTI mandrel-bent exhaust system bolted up and fit perfectly. TTI's headers and exhaust components are top quality, durable, and feature ease of installation. The TTI setup looks much cleaner in fit and finish with a polished ceramic coating and aluminized exhaust. We're certain the TTI components were worth more horsepower too with stepped headers, balance tube, and mandrel bending.
On top of the Wilson Manifolds...
On top of the Wilson Manifolds box is its famous strip- and engine-dyno tested, four-hole, tapered spacer. We removed its 1-inch open spacer and replaced it with its four-hole tapered spacer. This spacer switch added 10 hp and 12 lb-ft of torque at 4,300 rpm. Throttle response and drivability was much improved as well.
We tried leaning and richening...
We tried leaning and richening the air/fuel mixture, but went back to the original jettIng for max power. Dyno tuning helps street driving as well as lower e.t.'s.
A gear change from 3.55s to...
A gear change from 3.55s to 3.91s was a logical choice to take advantage of the wider, stronger, and higher powerband since the Indy head install. On the left is the 489 third member fresh out of the GTX with the spring-loaded, cone-clutch-type differential. On the right is a beefier, 489 unit built by Randy's Ring and Pinion. It features a solid-type spacer sleeve, clutch-type Powr-Lok differential, U.S. Gear 3.91 gearset, and Timken bearings. Red Line synthetic 75W90 gear oil and limited-slip break-in additive will provide great gear protection, reduce temperatures, and improve differential efficiency.