Summit Racing 505ci Mopar Stroker Power Test

664 HP, 677 LB-FT, ALL UNDER 5500 RPM ON 10.4 CR AND 91 PUMP GAS
For a street car, this thing will tear your head off. Take a look at the accompanying dyno sheet. This is a street friendly pump gas engine built with mail-order parts, primarily from Summit Racing. There's over 650 lb-ft of torque at 3500 rpm and 500 horsepower at 3900 rpm. Can more cam and more compression make more than this? Undoubtedly as the CNC'd Trick Flow heads will certainly support it, but this is a 91 octane pump gas street engine built to demonstrate the power potential of all the Trick Flow parts used in the upper engine assembly.
Take a look at the accompanying dyno sheet and note the Brake Specific Fuel Consumption numbers which are all in the .3-.4 range for the operative power band of this engine. This indicates the highly efficient combustion chambers of the Trick Flow PowerPort 270 cylinder heads. And note the rock steady oil pressure delivered by the Milodon billet oil pump and accompanying Pro Street oil pan and windage tray.
For stealthy street service you want a single four barrel engine like this in your Mopar today. It will hit a 3000-3500 rpm torque converter like a ton of bricks and surprise most challengers with an excellent view of your rear bumper. In the first three parts of this build we described how this engine was built and here we're going to highlight the results and further comment on some of the components that make it so strong on regular street fuel.
The engine was tested at Verbancic Brothers Racing Engines in Ontario, CA. Bob Verbancic and his crew have many decades of experience dialing in these combinations.  Note, the available dyno headers had 2-inch primaries which may have given up a bit or power and torque due to the engine's low operating range. The Summit Racing coated headers that will go in the car have 1-7/8 primaries which are more appropriate. We didn't want to drill holes in the good headers for the EGT probes.
The primary durability components that make this a bulletproof street engine include the Milodon cross-bolted billet main caps, precision line boring by QMP Racing, a precision machined SCAT forged stroker crank and forged Diamond pistons mounted on SCAT big block Chevy style rods with ARP 2000 capscrews. The SCAT crank, rods and Diamond pistons come as a ready-to-build rotating assembly from SCAT. These components anchor the short block with additional support from a Milodon external billet oil pump and Pro Street oil pan and stabilized by an ATI balancer.
The ATI Super Damper is another important component in maintaining the durability of the engine. There are two ways to go here. We used The ATI-917120 damper from Summit Racing. The front of this damper is configured with a big block Chevy bolt pattern for the accessory drive pulley which ultimately caused a problem because most of the available accessory drive kits are configured for the standard Mopar bolt pattern. As shown in Part 3 of this build we made it work with a few minor modifications. If you want to maintain the standard Mopar bolt pattern you need to use the ATI-917122E damper, also from Summit. There is also a difference in the balancer bolts for each damper.  The damper we used for our steel crank required the shorter bolt ARP-245-2501, which is 1.420 inch long. A cast Mopar crank requires the longer ARP-240-2501 which is 2.200-inch long. An easy way to remember this is that stock cast cranks take the long bolt and  steel cranks take the short bolt.
Without question, Trick Flow's PowerPort® 270 cylinder heads are the key power ingredient in this potent combination. These CNC ported heads maintain the long established Trick Flow tradition of excellence with high flow, high velocity ports and one of the most efficient Mopar combustion chambers we've seen as evidenced by by BSFC numbers in the .3 range across the entire operational powerband. In this case they required only 32 degrees total timing to make that power; further indicating the efficiency of the chambers. They are likely the best overall cylinder heads you can get for max effort RB Mopar applications of all displacements. With higher compression ratios and more camshaft timing we are confident they will support engines well into the 700 HP range and beyond. Perfectly complementing the PowerPort® heads is the Trick Flow Track Heat®, aluminum, single-plane, high rise intake manifold. It is perfectly matched to the heads and accepts all squarebore carburetors and throttle bodies. In our case, we feel we may have given up a few horsepower by not using a one-inch open carburetor spacer above the manifold. They increase plenum volume and help the fuel mixture make the turn into the runners more easily. With concern for hood clearance on our 1974 Cuda we opted not to use the spacer.
Trick Flow designed this combination as a package to include the Track Max® hydraulic roller camshaft and it is clearly a home run effort for Mopar lovers with large displacement stroker engines. The cam is ideal for hot street applications and plenty strong enough for drag strip use as well. Another major contributor to the overall power package is the extraordinary ring seal provided by Total Seal's new gas ported ring set. As seen here, the top ring is 1/16-inch thick and the gas ports across the top of the ring are .007-inch deep. These rings sealed up almost immediately and the added gas pressure behind the rings gave us great vacuum and not a trace of blow-by.
Total Seal's gas ported rings sealed so well the engine was pulling 1.8 inches of vacuum as soon as we took it to wide-open throttle. That was with the 950 carburetor. With a little help from Bob Verbancic who also owns The Carb Shop we discovered that the 950 is name only and that the 850 Holley actually has the larger venturis we needed. Switching to an 850 of the same model cured the problem. So if you're duplicating this, go for an 830-850 carburetor from Summit Racing. And, of course, another great power secret is the Johnson hydraulic roller lifters. The real advantage they offer is repeatable metering from cycle to cycle and thus consistent valve action on every event. They cost a little more, but knowing your valves open the same every time takes maximum advantage of the camshaft and it is well worth it. Isky is a primary dealer and you can order them directly from any Johnson Lifters dealer.
All in all a very successful project build that illustrates the power potential of carefully assembled mail-order parts from Summit Racing and the other manufacturers who participated. Please note, there are four parts to this story beginning with the block preparation and conversion to billet cross-bolted maincaps. Follow the links to the right to go directly to each story and note the detailed parts links at the bottom of each one. The will take you directly to the vendor sales pages for each part.