Let’s face it, some tests are just cooler and more fun than others!

Just what constitutes a cool engine build, you ask? Well, you start with a pinch of Stroker displacement, toss in, say, wilder cam timing and head flow, then finish it all off with boost from a turbo or turbos! Heck, let’s toss a blow-through carburetor into the mix, just to spice things up!

Lesser enthusiasts might be satisfied with any one of these components, but that’s not how we roll here at Summit Racing. If one or two of these things might be good, then all of them are definitely just right. It is with this wretched excess in mind, we decided to bring you a pair of boosted, blow-through (carbureted) Stroker tests.

In truth, we wanted to illustrate how effective blow-through carb combos can be, but why stop at just one test when two really brings the message home? Remember, there is no reason that the EFI guys should get all the love. Enthusiasts have been running boost through carbs long before EFI came around, and the thing is, it still works!

Follow along while we cover the blow-through boosted results on a 347 Ford and a 383 LS Stroker.

man holding camshaft box next to a turbo
Can you successfully run turbo boost through a carburetor? Yes, yes you can! (Image/Richard Holdener)

Test Motor #1: Turbo, Carb 383 LS Stroker (13.4 psi)

Before adding boost, we decided the first thing the boosted LS combo needed was more displacement. The 4.8L/5.3L iron block was taken to L&R Automotive in Sante Fe Springs, California for machining which included cleaning, boring, and honing to a final LS1 over-bore size of 3.905 inches (up from 3.780).

To this we added a 4.0 inch forged steel SCAT Stroker crank, a set of 6.125 inch 4340 forged rods from K1, and flat-top forged pistons from JE. In addition to being plenty strong, the JE pistons featured sufficient valve reliefs for our Stage 3, hydraulic roller cam from Brian Tooley Racing. The BTR Stage 3 Turbo cam offered 0.609/0.610 lift split, 230/235 degree duration split, and 114 +4 degree LSA.

Working with the BTR cam was a set of Trick Flow Specialties GenX 215 heads. What was special about the GenX 215 heads, you ask? How about revised valve angles (from 15 to 13.5 degrees), full CNC porting, and a 2.05/1.60 stainless valve package?

Feeding the ported heads and BTR cam was a single plane Edelbrock Victor Jr. Intake and (for the NA motor) Holley 750 HP carb. The MSD ignition controller was used to dial-in the timing curve on the carbureted combo. Run with 1-7/8 inch headers, the 383 combo produced peak numbers of 504 hp at 6,100 rpm and 479 lb.-ft. of torque.

Now it was time for some boost.

The LS turbo kit from CX Racing included tubular exhaust manifolds, Y-pipe, and a single 76mm turbo. The kit also featured its own wastegate, which we controlled with a simple manual wastegate controller (bleed valve). The kit was designed to accept a T4 turbo, but we replaced the supplied 76mm turbo with a larger GT45-style turbo. The V-band clamps allowed easy hook up, but it should be noted that the proximity of the exhaust tubing to the spark plugs and wires on this kit was less than ideal.

We ran this turbo system through a CSU blow-through 850 carb. Thanks to jetting and boost-referenced power valves, optimizing the carb was no more difficult than jetting the NA version. The blow-through, turbo 383 was run with no intercooler on 100 octane race fuel. Run in this manner, the turbo 383 produced 872 hp at 6,000 rpm and 803 lb.-ft. of torque at 5,400 rpm at 13.4 psi. Run at this boost and power level, we suspect we were nearing the absolute limit of the turbo, as the combo produced a falling boost curve. We would later run this 383 with EFI and a larger Precision turbo to the tune of over 1,000 horsepower, but the carb combo worked well on this 383 LS Stroker.

Test Motor #2: Turbo, Carb 347 Ford Stroker (12.4 psi)

To test the merits of a blow-through set up on the Ford, we built a 347 Stroker with forged internals that included a 4340 forged crank and rods combined with forged flat-top pistons from JE. With sufficient strength and displacement, we added the necessary power producers, including heads, cam, and intake.

AFR supplied a set of new CNC-ported 205 Renegade cylinder heads which were combined with a COMP XFI hydraulic roller cam and single plane, Funnel Web intake. Effective for both normally aspirated and boosted combinations, the Comp XFI cam offered a 0.579 Lift, a 236/248 degree duration split, and 114 degree LSA. COMP also supplied the necessary lifters, double roller timing chain, and hardened pushrods.

The AFR Renegade heads offered flow rates exceeding 330 cfm, or enough to support over 660 (normally aspirated) horsepower. They were obviously more than enough for our 347. Ensuring plenty of high-rpm power, the single-plane, high-rise Funnel Web intake was fed by a Holley 950 Ultra HP carburetor and fired by an MSD billet distributor. In normally aspirated trim, the 10.8:1, carbureted 347 Stroker produced 476 hp at 6,400 rpm and 438 lb.-ft. at 5,000 rpm.

Turbo time!

The Ford twin-turbo kit unit included stainless exhaust manifolds & tubing, aluminum intake tubing, and all the clamps and couplers to connect the system. The kit also featured all the oil feed and drain fittings, braided oil feed (but not rubber drain) lines, and a sizable air-to-air intercooler. The exhaust manifolds were designed to accept T3 turbine housings, meaning they will accept any size T3 turbo. We installed a pair of GT3582 turbos from Max Speeding Rods. Each Max Speeding turbo was capable of exceeding 500 hp, so they combined to provide over 1,000 hp worth of flow potential.

Before running in anger, it was necessary to orient the compressor and turbine housings to line up the oil feed and drain fittings. Once oriented, we bolted the turbos to the T3 flanges. The wastegates were also mounted to the provided wastegate flange on the manifold, but this was later modified to accept a pair of larger 45mm Hyper-Gates from Turbosmart to properly control the boost.

All the boost was channeled through the air-to-air intercooler and finally to the awaiting CSU blow-through carb. After installation of a pair of Max Speeding GT3582 turbos and CX Racing air-to-air intercooler, the blow-through 347 produced peak numbers of 858 hp and 777 lb.-ft. of torque at 12.4 psi.

Another win for the blow-through carb contingent!

Graph 1: 383 LS Stroker-NA vs. Blow-Through Turbo (13.4 psi)

engine dyno chart
Who thinks that carburetors and turbo don’t make good power? If you thought that, these results might just change your mind, as blowing through the CSU 850 Holley carb resulted in some serious power. In fact, we all but maxed out the single turbo on this blow-through Stroker. To prep for the boost, the 383 featured a SCAT Stroker crank combined with forged rods and pistons. Topped with Trick Flow Gen X 215 heads, a Victor Jr. Intake and 750 Holley, the NA 383 produced 504 hp at 6,100 rpm and 479 lb.-ft. of torque at 4,900 rpm. After adding the single GT45-style turbo (measured 72mm) and cranking it up to 13.4 psi, the peak power numbers jumped to 872 hp and 803 lb.-ft. of torque. (Dyno Chart/Richard Holdener)

Graph 2: 347 Ford Stroker-NA vs. Blow-Through Turbo (12.4 psi)

engine dyno chart graph
To illustrate that blow-through turbos don’t play favorites, we applied boost through the same 850 CSU carb on a small block Ford Stroker. Like the 383 LS, we stepped up in cubic inches on the Ford small block as well. Using a Dart SHP block, we built a 347 Stroker using a forged, 3.40 inch stroke crank combined with a set of 5.40 inch rods and forged, flat top pistons. The Stroker was stuffed with an XFI 236 cam then topped with AFR 205 Renegade heads and a single-plane, Funnel Web intake. The Run with long-tube headers and an MSD distributor, the NA 347 produced 476 hp at 6,400 rpm and 438 lb.-ft. of torque at 5,000 rpm. After installation of a pair of Max Speeding GT3582 turbos and CX Racing air-to-air intercooler, the blow-through 347 produced 858 hp and 777 lb.-ft. of torque at 12.4 psi. (Dyno Chart/Richard Holdener)
head gasket resting on engine deck
Test motor number one was a 383 Stroker LS. We achieved the 383 displacement by replacing the factory crank, rods, and pistons with a 4.0 inch SCAT Stroker, 6.125 inch rods, and forged (dish) pistons. (Image/Richard Holdener)
btr camshaft box on table
For this carbureted turbo test, the 383 was equipped with a Stage 3 turbo cam that offered a 0.609/0.610 lift split, 230/235 degree duration split, and 114 +4 degree LSA. (Image/Richard Holdener)
man installing trick flow cylinder head
We topped the 383 Stroker with a set of CNC-ported, TFS GenX 215 aluminum heads. (Image/Richard Holdener)
single plane intake manifold on an ls engine
For our carbureted application, we chose a single plane Edelbrock Victor Jr. intake manifold. (Image/Richard Holdener)
msd ignition box sitting on an engine
To properly control the ignition on the carbureted LS, we chose an MSD ignition controller. MSD offered a system with a MAP sensor to control timing versus load and rpm. (Image/Richard Holdener)
ls engine on a dyno
Run on the dyno in naturally aspirated trim with a 750 Holley carb, the low-compression 383 produced peak numbers of 504 hp at 6,100 rpm and 479 lb.-ft. of torque at 4,900 rpm. (Image/Richard Holdener)
turbocharger on an engine dyno
After establishing a baseline in naturally aspirated trim, we installed a turbo system that featured dedicated turbo headers feeding a Y-pipe and single GT45-style turbo. The turbo system also featured a provision for a Turbosmart 45mm Hyper-Gate wastegate. (Image/Richard Holdener)
carburetor atop an engine
The 750 Holley carb run on the NA motor was replaced with a dedicated 850 blow-through carb from CSU. (Image/Richard Holdener)
turbocharged engine on a dyno run
Run under boost on 100 octane race fuel, the blow-though 383 pumped out 872 hp and over 800 lb.-ft. of torque at 13.4 psi. We were very close to the flow limit of the small(ish) turbo on this 383. (Image/Richard Holdener)
pistons in an engine block
Test motor number two was a 347 Ford Stroker that started out life with a Dart block stuffed with a forged Stroker crank, 5.40 inch (forged) H-beam rods, and forged flat-top pistons. The pistons featured valve reliefs to allow for even wilder cam timing. (Image/Richard Holdener)
camshaft going into an ls engine
COMP Cams supplied a healthy XFI 236 hydraulic roller cam that offered 0.579 lift, a 236/248 degree duration split, and 114 degree LSA. (Image/Richard Holdener)
view of intake side of an AFC Cylinder head
Topping the 347 Stroker short block was a set of CNC ported, AFR 205 Renegade aluminum heads. (Image/Richard Holdener)
ls engine during a dyno pull
Run on the dyno with a Funnel Web intake, 750 Holley carb, and 1-3/4 inch, long-tube headers, the 347 Ford produced 476 hp at 6,400 rpm and 438 lb.-ft. of torque at 5,000 rpm. (Image/Richard Holdener)
turbo side of an ls engine on dyno
After running the 347 in naturally aspirated trim, we installed a custom turbo system consisting of shorty-style, tubular headers feeding a pair of smaller T3 turbos from Max Speeding. It was necessary to change the wastegate configuration (shown) for proper boost control. (Image/Richard Holdener)
impeller on a turbocharger on an ls engine
Because we had aspirations of making 1,000 horsepower later, we selected a pair of GT3582 turbos from Max Speeding Rods. (Image/Richard Holdener)
large intercooler for an engine dyno test
Boost from this custom twin-turbo set up was run though this air-to-air intercooler from CX Racing. (Image/Richard Holdener)
view down a carburetor during an ls engine dyno test
The Ford Stroker was equipped with the same 850 cfm CSU blow-through carb run on the 383 LS motor. (Image/Richard Holdener)
intercooled & turbo engine on an dyno test pull
Run at 12.4 psi, the twin-turbo, blow-through 347 Stroker produced 858 hp at 6,500 rpm and 777 lb.-ft. of torque at 4,900 rpm. (Image/Richard Holdener)

Keywords
blow-through carburetor, boost, Intercooler, supercharger, turbo
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Author: Richard Holdener

Richard Holdener is a technical editor with over 25 years of hands-on experience in the automotive industry. He's authored several books on performance engine building and written numerous articles for publications like Hot Rod, Car Craft, Super Chevy, Power & Performance, GM High Tech, and many others.