Indy Cylinder Heads - Headed To Indy
Indy SR Heads-More Than Stock Replacements
From the January, 2004 issue of Mopar Muscle
By Dan Foley
Photography by Dan Foley
Mike Barton of RBRE handled...
Mike Barton of RBRE handled the flowbench duties for the Indy SRs. Having records of the many Indy heads they have already flowbenched, we were pleased with the flow numbers after our porting efforts. The Indy SR heads really came alive after we opened up the intake openings to the Max Wedge size.
All it took was a call from a long-time Mopar friend, Vic Palumbo. "Hey Dan, I bought a set of Indy SR [Stock Replacement] heads. Could you port and bolt 'em on my '67 GTX?" My reply: "Sure Vic-providing we could use your car for testing. The Indy SRs would have to prove themselves against a set of 906 heads with the typical modifications." Vic didn't realize the change would require new headers and an installation kit from Indy Cylinder Heads, which includes longer pushrods, an external oil line kit, and head bolts. One thing not included was the valley cover plate that would be necessary to perform the head swap. We ordered a set of TTI headers, specific for the Indy heads, along with a complete TTI exhaust system. Also ordered was the aforementioned install kit and valley cover from Indy. Vic's '67 already had sufficient hood clearance with a Hemi hoodscoop, and at this point we felt we were good to go on with the swap.
Before ponying up the jack for a set of Indy heads for your big-block, consider this: Your B/RB will need at least a 10:1 compression ratio, a high-lift, high-velocity cam (preferably a solid roller), a high-stall converter (matched to the cam, heads, and gearing), and steep gearing of 3.91s or better. The 440 in the GTX is a 10.5:1 Ray Barton Racing Engines (RBRE) short-block with a Comp Cams hydraulic cam with .501 inch lift, and a duration of 244 degrees at .050. The 906 heads came from a local machine shop with the larger 2.14/1.81 valves, light bowl work, and gasket matching. On the flow bench the iron heads were good for 241 cfm at .500 inch lift (flow stalled above .500 inch lift). Stock 906 heads with the 2.08/1.74 valves will usually flow 210-220 cfm at .500 inch lift.
Our original intentions were to fully port and polish the Indy SRs, back-cut the intake valves, and retain the stock 906-size intake port openings. We brought the aluminum castings-one ported and one stock-to the RBRE facility in nearby eastern Pennsylvania. Mike Barton flowed the SRs (Mike has flowed and ported many Indy heads), and back-cut the intake valves to 28 degrees. Satisfied with the flow numbers, we called Russ Flagle at Indy Cylinder Head (ICH) about our results. Russ highly recommended we enlarge the port openings to the Max Wedge size. Max Wedge ports are typically 1/2 inch taller than a stock 906 port. We also removed .150 inch from the pushrod pinch area and blended that area as well. The Max Wedge-size port openings raised the flow numbers at low, mid, and high lift through the roof (see charts). Indy sells the SRs already CNC-ported with the Max Wedge-size intakes. This will save you many hours of porting.
We wanted to reuse the Edelbrock Performer RPM intake, and gasket match it to the Max size. The problem is, there's not enough material to do so. This prompted us to use the Indy 440-2D RB dual-plane intake. This intake features taller runners and larger ports, but is similar in design to the Performer RPM, which utilizes stock 906-size port exits. Fortunately, the Indy intake had plenty of material for us to port match to the Max Wedge size. This street/strip intake delivers a high, broad torque range with excellent throttle response-great for street-driven cars. The same 850 Speed Demon carburetor was employed for all strip and dyno duties.
Install And Combo
So far, the head swap required the Indy intake installation kit and TTI headers, because the Indy exhaust ports are 3/4 inch higher and 1/2 inch wider than stock ports. Earlier we mentioned a high-velocity cam would be advantageous in promoting air velocity with Indy's larger intake ports. So we tossed the stock 1.5-ratio rockers in favor of Indy's 1.6-ratio roller-tip rockers. We also enlisted a pair of Indy's thick-wall rocker shafts. The SRs can use any stock-type replacement adjustable rocker, and there is no need for expensive offset rockers. The 1.6 rockers will help the .501-inch-lift Comp cam to act like it has .530 inch valve lift while speeding up the valve and airflow.
The Indy head on the bottom...
The Indy head on the bottom has noticeably larger valve bowls than a stock 906. Also notice on the Indy head the intake port to the left has been ported while the one on the right has not. Even a fully ported cast-iron 906 or 452 head is not as good as a stock Indy SR. The Indy features angled plugs (toward the exhaust valve) and a heart-shaped combustion chamber, which makes this head more efficient.
The Indy head (on the right)...
The Indy head (on the right) features intake ports that are 1/2 inch higher than stock, which will promote better airflow and raise the intake manifold 1/2 inch (be sure to check hood clearance). Because of this, an Indy valley pan is also needed. Stock-style intakes, rocker shafts, rocker arms, and valve covers will work with the Indy heads.
The raised exhaust ports on...
The raised exhaust ports on the Indy heads will require custom headers to be used (we ordered a set of from TTI). The rocker shaft pedestals raise the rocker shaft assembly approximately 1/2 inch higher. This equates to a set of longer pushrods as well to run the Indy heads.
Here we can see how the Indy...
Here we can see how the Indy exhaust port flange is 1/2 inch further out than the stocker. The manifolds or headers will sit outward 1/2 inch (another reason why custom headers are needed). Keep in mind the Indy exhaust ports are much more efficient at exhaling the waste to deliver more horsepower through fewer pumping losses.
The intake port on the left...
The intake port on the left is stock. The SR comes bowl-blended where the hardened-steel valve seat meets the aluminum. The intake port on the right was fully bowl-blended, polished, and the valveguide boss trimmed. Not seen is the short turn of the port floor that was polished with 100- then 220-grit sanding rolls.
(A)The intake port on the...
(A)The intake port on the left shows the pushrod pinch area. We ground .200 inch from the pushrod pinch (beware of core shift). (B) We checked and still had about .120 inch thickness (.100 inch is the absolute minimum) before polishing the entire port with 100-grit barrel rolls.
Before we tore the 906 heads...
Before we tore the 906 heads and Edelbrock RPM intake off, on SLP's chassis dyno the 10.5:1-compression, 906-equipped 440 put out 366 hp to the rear wheels-quite a healthy start to improve on.
The changeover to the Indy SRs was as simple as bolting on a pair of stock heads, with the exception of the Indy valley plate. It must be bolted on before the heads are installed. Remember that upgrading from 906s to Indys does require longer pushrods and the installation of an external oil line kit for the rocker assembly. We were impressed by how well the Indy intake ports aligned with the ports on the heads.
Initially, we set up the hydraulic lifters at zero preload then turned the rocker adjusters in another quarter turn. The quarter-turn setting made for a noisy valvetrain, even after a 20-minute warm-up. Ken Lazarri at ICH suggested we try a three-quarters to a full turn from zero lash. At three-quarters of a turn the valvetrain was quiet and the 440 was more responsive than ever.
The revamped RB was warmed up and checked for any possible fluid leaks. A half-hour ride was taken to bring everything up to operating temp. Then the oil and filter were changed. The oil we used was Mobil1 synthetic 15-50 weight. The carb was adjusted and the idle was set at 1,100 rpm. The timing was set the same as it had been with the 906s (42 degrees total, and all in by 2,000 rpm). The shakedown drive on the back roads near the shop told us the Indy heads greatly increased the all-around powerband, especially at 5,000 to 6,000 rpm according to our seat-of-the-pants dynamometer.
Baseline testing with the 906 heads on the chassis dyno at SLP Performance Parts showed us 366 hp at 5,600 rpm at the rear wheels.
The Indy 433
We were anticipating substantial gains from the Indy heads, therefore it was back to the SLP dyno to see how much we really gained. On our baseline pull we were impressed to find we gained 60 peak horsepower at the same 5,600 rpm. Peak torque was up 20 lb-ft at the same 4,200 rpm. The powerband was broadened so much, the 440 made 90 more horsepower at 6,000 rpm. With the stock heads, power dropped off after peaking at 5,600 rpm.
We wanted our dyno time to be useful, so we brought along a timing light, a box of carb jets, a Wilson four-hole tapered carb spacer, and a K&N X-Stream air-cleaner lid. Our first effort toward tuning for more power was in the timing department. Baseline timing was 42 degrees, then 38, then 35, and finally we found seven more horses at 40 degees total timing. Peak power was now up 67 hp (433 hp at 5,600 rpm) over the ported 906 heads.
Next, the chrome air-cleaner lid was swapped for a K&N X Stream airflow top. The K&N lid increased the throttle response, torque, and horsepower. Power was up 6 hp and 6 lb-ft of torque at 4,700 rpm. Strangely enough, peak horsepower at 5,600 rpm remained the same. Average horsepower and torque numbers were up between 4,000 and 6,000 rpm (See charts). The K&N X Stream is a tested winner in lowering e.t.'s, and now it added horsepower on the dyno.
The 906 and Indy heads' baselines were done with the same 1-inch open spacer under the Demon 850 carb. We swapped the open spacer for a Wilson Manifolds tapered four-hole spacer. In previous strip and engine dyno testing, the Wilson spacer has demonstrated respectable e.t. reductions and increased power. This time, the proven spacer gained us 10 hp and 12 lb-ft of torque at 4,300 rpm over the open-hole spacer. Horsepower and torque were up across the board, but ironically remained the same from 5,500 to 6,000 rpm.
The K&N X Stream air-cleaner lid and the Wilson spacer helped us out enough to move on to the carburetion. We expected the 850 Demon's 84 primary and 88 secondary jetting to be on the rich side (a puff of black smoke exited the pipes when nailing the throttle). Leaning out the secondaries to 85s lost us 8 hp. A pair of 90s was then tried, but power was still down. With that, we returned the jetting to the initial 84 and 88, which restored maximum power to the rear wheels.
A 28-degree back-cut was given...
A 28-degree back-cut was given to each intake valve at Ray Barton Racing Engines' facility. Back-cutting the intake valve always improves the low- and mid-lift flow. This modification also improves throttle response and drivability.
The Max Wedge gaskets demonstrate...
The Max Wedge gaskets demonstrate the smaller 906 intake-port size. Gasket matching raises the roof of the ports 1/2 inch higher. Flowbench numbers went through the roof after we opened the heads to Max Wedge size. The Indy intake also received port matching, but at .050 inch smaller than the gasket all around. This can prevent air turbulence, a possibility when the motor is bolted together.
One major difference before...
One major difference before bolting on the Indy heads is to install the Indy valley plate first. The valley cover is sealed with RTV at the end rails and where the head's deck surface meets the edge of the valley plate. We regret we didn't opt for the two-piece removable valley plate for future cam swaps so it can be done without removing the heads.
The Indy SRs bolted right...
The Indy SRs bolted right up to seal and capture the valley plate. Notice the large Max Wedge-size intake port openings. Box stock, these castings flowed 288 cfm at .700 inch lift. With extensive porting and polishing, they flowed 357 cfm at .700 lift. Even in stock form, these heads are proven performers.]
Adjustable rockers are a must...
Adjustable rockers are a must to achieve proper lifter preload (hydraulic) or valve lash (solid). We moved up to 1.6-ratio rockers from Indy. This meant the .501-lift Comp Cams stick would have .531 lift at the valve with the 1.6 rockers. The 1.6-ratio rockers will also aid the air velocity going through the larger-than-stock ports. Out of focus are the external oil lines at the rear of the heads.
Once the timing was set, we...
Once the timing was set, we decided to do some air cleaner testing. The same 850 Demon Carburetor and 4-inch K&N filter with chrome lid were employed for baseline pulls with the iron and aluminum heads. Changing to the K&N X Stream air-cleaner lid netted us 6 hp and 6 lb-ft of torque at 4,700 rpm.
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
|Port & Polish|
|Port & Polish|
With Back Cut and
|Lift||Stock||Ported||Ported & Polished|
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.