Ford Mustang Pro Comp Carbureted Turbo Engine
Dig Into This 1,000-Plus-Horsepower, 438-Inch Stroker Carbureted Turbo Torture Test.
From the August, 2010 issue of Muscle Mustangs & Fast Fords
By Richard Holdener
Can you really run a carburetor...
Can you really run a carburetor on a turbo stroker motor? Despite the turbo kit from HP Performance being designed for a 5.0L fuelie motor, it worked perfectly with the modified Holley carb from CSU.
At MM&FF, we just love it when a manufacturer hands us parts and tells us to go beat the living snot out of 'em. Not that we're especially abusive here, but we know our readers love nothing more than to see some big, fatty power numbers. In short, this was the perfect opportunity to subject a new block, rotating assembly, and ported cylinder heads offered by ProComp Electronics to the rigors of the dyno. Given the author's affinity for all things forced induction, what better way to demonstrate the strength of the new components than by combining big displacement with boost to create a pressurized power plant?
Rather than take the usual route of supercharging an EFI motor, we decided to combine a turbocharger with carburetion. Though certainly not a low-buck approach, the use of a carburetor and conventional distributor demonstrates an effective alternative to a factory or standalone EFI engine management system. The carbureted combination also allows us to effectively stress test the new block, crank, and even the cylinder heads, as we will settle for nothing less than an honest 1,000 hp!
Given the power potential,...
Given the power potential, we needed something stronger than the production block. ProComp supplied a new heavy-duty Windsor block for this build. The block was precision-machined by L&R Automotive and features all the usual strengthening tricks, including splayed fou-bolt main caps. The ProComp block is stuffed with a 4340 forged-steel, 4.1-inch stroker crank, and matching 4340 forged rods, also from ProComp.
The first step was to have the new block properly machined. The ProComp block was taken to L&R Automotive. Our 351W block featured a 4.125-inch bore size, which we combined with a 4.10-inch crank to produce a finished displacement of 438 ci. The block was honed and all the critical elements checked prior to assembly. The only oddity during the process was that the main bolts featured metric heads but standard threads. They can easily be replaced with ARP hardware, but we ran them as delivered.
The block was plenty beefy and featured splayed four-bolt main caps, and thick decks and cylinder walls. Basically it was everything the stock 5.0L and 351 Windsor blocks are not. Having split stock blocks in half from excessive power, having a solid foundation is a must when probing the 1,000hp mark.
Naturally, our turbocharged...
Naturally, our turbocharged stroker required forged pistons. Probe Racing supplied dished pistons (4.125-bore) for our turbo motor. When combined with the 70cc combustion chambers on our ported heads, the static compression checked in at a boost-friendly 9.2:1. Note also the use of Fel-Pro MLS head gaskets and 1/2-inch ARP head studs-a must for boosted applications.
In addition to the block, ProComp also supplied a 4340 forged steel crank and matching 6.20-inch connecting rods. The long rods were needed to clear the equally lengthy 4.10-inch stroke. To these we added forged (dished) pistons from Probe Racing to complete the 9.2:1 rotating assembly.
Given their extensive lineup of components, ProComp was happy to supply its CNC-ported cylinder heads. We tested a set of these heads previously in MM&FF on a 408 stroker with good success, so we knew they had potential.
A portion of the success (both...
A portion of the success (both normally aspirated and turbocharged) goes to our cam profile. Cam Research Corp supplied the hot roller cam for our stroker motor. The aggressive profile featured a 0.736/0.727 lift split, a 254/252 duration split, and a (turbo-friendly) 112-degree lobe separation angle.
When it comes to making big power with a turbo or blower, the key is to start with a powerful normally aspirated combination. Wanting to maximize the power output of the motor prior to the application of boost, we sent the CNC-ported ProComp heads to the flow wizards over at Dr. J's. Dr. J's has extensive experience with the ProComp Ford heads, and took our already-good heads and made them better.
According to Dr. J's, the valve job is a critical upgrade to the ProComp heads. In addition, Dr. J's performed some minor porting and blending to finalize the castings. They can perform the same work to the as-cast heads, but the level of porting is much more extensive to reach the 300-plus-cfm mark.
When all was said and done, the heads flowed 321 cfm on the intake and 247 cfm on the exhaust at 0.800 lift. The ported heads were secured using 1/2-inch ARP head studs and Fel Pro MLS head gaskets designed for our 4.125 bore.
The Cam Research Corp roller...
The Cam Research Corp roller cam required solid roller lifters from Comp Cams (PN 836) along with a set of Magnum pushrods. The ProComp block can be drilled to accept the factory hydraulic lifter assembly, or a link-bar setup can be used (similar to our roller lifters).
With one of the three major power producers taken care of, we turned our attention to the cam and intake manifold. Given the displacement and intended power level, we chose a single-plane intake. As luck would have it, Dr. J's had an Edelbrock Super Victor that was all ported and matched to the ProComp heads. Since we were running a carburetor, the ported Super Victor seemed like the perfect choice.
Proper cam timing for our boosted stroker was provided by the Ford cam experts at Cam Research Corp. Having had such good success in the past, we were anxious to see the cam specs for our turbo stroker.
Since we were using a ProComp...
Since we were using a ProComp four-bolt block, we decided to complete the motor with a set of CNC-ported ProComp aluminum Ford heads. We were looking for some serious power, so we shipped the ProComp heads to Dr. J's for further massaging. Dr. J's has done extensive work with the ProComp castings and has taken an already good head (we tested a set of MM&FF on a 408 with positive results) and made it exceptional.
Cam Research supplied what we thought was a pretty mild profile, at least in terms of duration. Taking full advantage of our high-flowing heads, the solid roller cam supplied for our 438 checked in with a healthy 0.736/0.727 lift split, a 254/252 duration split, and a boost-friendly 112-degree lobe separation.
Though the 254/252 duration split seemed tame, the results were nothing short of amazing, both normally aspirated and turbocharged. The Cam Research Corp cam was combined with roller lifters, a double-roller timing chain, and hardened pushrods, all from Comp Cams. The final touch of valve train hardware was a set of 1.7-ratio gold roller rockers.
The extra porting performed...
The extra porting performed by Dr. J's produced impressive flow numbers, both peak and the all-important low-lift numbers. The work included a custom valve job and additional hand-porting to finish up the already CNC-ported heads from ProComp. Dr. J's can also work its magic on a set of as-cast heads, but the work is much more extensive. Once completed, the heads flowed 321 cfm on the intake and 247 cfm on the exhaust at 0.800 lift.
The guys at Cam Research Corp...
The guys at Cam Research Corp specified a set of 1.7-ratio rockers for use with the roller cam, so we installed a set of Crane Gold rockers. Comp cams supplied the valvesprings and retainers for our roller cam application.
Since they already ported...
Since they already ported the ProComp heads, we enlisted Dr. J's to work some magic on the intake manifold. The Edelbrock Super Victor was fully ported and (like the heads) matched to the Fel Pro 1262R intake gaskets.
Additional goodies employed...
Additional goodies employed on the 438 included a Milodon oil pan, MSD distributor, and 1,000-cfm Holley HP series carburetor. Though a tad on the small side for this application, the stroker exhaled through a set of 1 3/4-inch Hooker Super Comp headers to the tune of 605 hp at 6,500 rpm and 568 lb-ft at 4,500 rpm. Now it was time for some boost.
Prior to adding boost, we ran the 438 stroker in normally aspirated trim. To complete the stroker, we installed a Milodon drag-race oil pan, 1 3/4-inch Hooker Super Comp headers, and an MSD billet distributor. Additional components on the normally aspirated motor included cast-aluminum valve covers, plug wires, and 28-ounce damper, all from ProComp. Also present was Lucas 5W-30 oil, a K&N oil filter, and Denso Irridium plugs (IQ27).
In normally aspirated trim, the 438 was run on pump gas with a Holley 1,000-cfm HP-series carburetor. After the break-in procedure and some minor tuning, the normally aspirated 438 pumped out 604 hp at 6,500 rpm and 568 lb-ft at 4,500 rpm.
Running boost required swapping...
Running boost required swapping out the 1,000-cfm Holley for a dedicated forced-induction carburetor. Having had such success in the past with this CSU carburetor on blow-through supercharged applications, we were anxious to try it on a turbo motor.
Demonstrating the torquey nature of stroker motors was the fact that the 438 offered no less than 510 lb-ft from 3,500 rpm to 6,200 rpm. Making this all the more impressive, the power numbers came from a combination featuring a blower/turbo cam and a static compression ratio of just 9.2:1. Were we to build this motor as a dedicated normally aspirated combination, we'd up the compression with flat-top pistons (to replace the 29cc dish units), have Cam Research Corp do a wilder cam with a tighter lobe separation and more duration, and install 17/8-inch or even 2-inch step headers. Keeping the compression and cam timing at boost-friendly levels meant we were now free to install the turbo.
Since we just tested a 302 with the turbo kit from HP Performance in Roswell, New Mexico, selecting a turbo kit for the 438 stroker was as simple as pulling it off the previous test motor. The slip-fit cross-over tube allowed the turbo kit to fit both 302 and wider 351 applications. The kit from HP featured dedicated, tubular exhaust manifolds with V-band clamps, a front-mounted air-to-air intercooler, and Jet-Hot coated tubing. Though designed for a fuel-injected 5.0L (or 5.8L), the kit worked perfectly on our carbureted stroker application with just a few minor upgrades.
Feeding the CSU carburetor...
Feeding the CSU carburetor was a CSU carb bonnet. We liked the fact that this bonnet was not directional and could be mounted in any orientation. This was important as our turbo kit from HP Performance was originally designed for a 5.0L fuelie application. A small section of tubing was all that was needed to connect the discharge tube to the bonnet.
The first component in the line of upgrades was obviously the carburetor itself. Our blow-through (works on both supercharged and turbocharged applications) carburetor came from Carburetor Solutions Unlimited (CSU). The CSU carburetors are machined and tuned specifically for use on blow-through applications, providing precise metering under all normally aspirated and boosted conditions, including transitions.
Having had such success in the past with the CSU carburetors on supercharged motors, we were anxious to give this one a try on our turbocharged stroker. It is easy to tune a blow-through carburetor to either run well at full throttle or under cruise conditions, but CSU has mastered both. A small section of tubing was necessary to connect the discharge tube from the intercooler to the CSU carburetor bonnet.
The kit from HP Performance...
The kit from HP Performance featured complete Jet-Hot coating and was the very same one we used on the 302 test run previously for MM&FF. Running a smaller turbo and low boost pushed that smaller 302 over 620 hp, but this same kit would work equally well on this 1,000hp application.
As indicated previously, the turbo kit was originally used on a milder 302 application. Though we managed to exceed 600 hp with the supplied turbo, an upgrade was in order, but not before we swapped out the 44mm Tial wastegate. Apparently, the 44mm wastegate was too small to properly control the boost pressure supplied by the Comp Turbo-boost creep resulted in an escalating boost curve.
Coming to our rescue were the guys from Turbo Smart in the form of a 45mm Hyper-Gate. According to Turbo Smart, the 45mm Hyper-Gate offers a 20 percent increase in flow over the smaller 44mm wastegate. Installation of the Hyper-Gate cured the rising boost curve and provided complete boost control. A manual boost controller was used to bleed the pressure signal to the wastegate, thus allowing us to adjust the boost pressure from 7 psi (the wastegate spring setting) to over 15 psi (or more with a spring upgrade).
To minimize the charge temperature,...
To minimize the charge temperature, the turbo kit from HP Performance featured an efficient air-to-air intercooler. Airflow through the core was supplied by a dedicated fan during testing.
The final upgrade was the turbo itself. Comp Turbo supplied a 74mm turbo for our stroker. The 74mm was a slick piece of equipment, featuring a billet center section plumbed for water-cooling, though we didn't run it in this configuration. Externally, it didn't look much bigger than the 60mm run on our 600hp 302, but boy did it flow like a bigger unit. Using the 74mm turbo, we were able to exceed 950 hp, but it wasn't quite large enough to reach 1,000 hp. A quick phone call and trip to Comp Turbo resulted in an upgrade to an 80mm impeller and housing. Using this new configuration, we were able to not only reach 1,000 hp, but exceed it by producing peak numbers of 1,037 hp at 6,000 rpm and 957 lb-ft of torque at 5,100 rpm. Torque production actually exceeded 900 lb-ft from 4,500 rpm to 6,000 rpm.
With minor jetting, the CSU carburetor provided a safe air/fuel mixture below 12.0:1, while the total timing was kept conservative at just 21 degrees. Combining the air-to-air intercooler and cooling from the fuel supplied by the carburetor resulted in an ultra safe combination that could easily run on pump gas (we ran ours on race fuel to be safe).
Despite the stress, the ProComp block, rotating assembly, and heads impressed us with the ability to support these extreme power levels.
The 44mm Tial wastegate supplied...
The 44mm Tial wastegate supplied with the turbo kit was unable to control the boost, so we swapped over to a 45mm Hyper-Gate from Turbo Smart. According to Turbo Smart, its 45mm wastegate offers a 20 percent increase in flow. Boost creep was no longer an issue with the larger wastegate.
The standard Fox-chassis turbo...
The standard Fox-chassis turbo kit from HP Performance comes with a 60mm turbo, but upgrades are available for increased boost and power potential. To reach the 1,000hp mark, we installed this 80mm turbo from Comp Turbo in San Dimas, California. After just missing 1,000 hp with the smaller 74mm turbo, they quickly upgraded the impeller to the 80mm version, and we were instantly rewarded with over 1,000 hp.
ProComp 438-NA vs. Turbo (12.8...
ProComp 438-NA vs. Turbo (12.8 psi)
This 438 stroker was powerful both in normally aspirated and turbocharged trim. Despite a static compression ratio of just 9.2:1, it produced 604 hp and 568 lb-ft of torque. In fact, torque production exceeded 510 lb-ft from 3,500 rpm to 6,200 rpm, making this one impressive street stroker. Adding boost with the 80mm turbo from Comp Turbo resulted in serious ponies. The combination topped the 1,000hp mark by posting peak numbers of 1,037 hp at 6,000 rpm and 957 lb-ft at 5,100 rpm. Torque production exceeded 900 lb-ft from 4,500 rpm to 6,000 rpm. The wastegate upgrade from Turbo Smart controlled the boost perfectly, and given the use of the air-to-air intercooler and CSU carburetor, we see no reason why this combination wouldn't run safely on pump gas.
To improve strength and reduce...
To improve strength and reduce weight, the 80mm (ball bearing) turbo from Comp Turbo features a trick billet center section set up to receive water cooling.
Run on the engine dyno at...
Run on the engine dyno at 12.8 psi, the turbocharged 438 stroker produced peak numbers of 1,037 hp and 957 lb-ft of torque. Stressed to impress, the ProComp block easily shrugged off power and torque numbers that would have split a production block right in half.