Engine performance is dependent on how much air and fuel can be taken into the engine and then fully combusted to produce power. While improving air flow into the engine can involve replacing everything from the air filter to the cylinder heads, one must realize that overall air flow can only be as high as the most constrictive part allows. After replacing the stock air filter and adding a few other hop-ups, the throttle body itself was now restricting the flow of air into our V-8 engine. Holley Performance had the perfect solution to our engine needs, suggesting we use their High-Flow EFI throttle bodies.
Holley makes performance throttle bodies (TBs) for a variety of applications including many EFI Chevys, the Magnum V-6 and the V8 found in '94-'01 Rams, '93-'98 Grand Cherokees, and '97-'03 Dakotas and Durangos. These beautiful 2x52mm TBs are CNC machined from 6061 aluminum billets and clear anodized. They are designed for mildly modified engines where the stock throttle body chokes the air flow to the upgraded performance parts. For instance, if your new intake manifold will flow close to 1000 cfm while your stock throttle body restricts air flow to 750 cfm, then that new manifold isn't going to be capable of reaching the improvements it was designed to achieve.
While the Holley High-Flow TBs will increase air flow at all rpm ranges, the most noticeable effects will be recognized at the lowest engine speeds. During these times, the butterfly valves that regulate air flow into the dual venturis are only slightly open, creating the most restrictive flow of the TB's operation. The extra flow provided by the smoothed out venturi entrances accounts for a larger percentage of the overall air flow. The engine is no longer as starved for air, more specifically the oxygen in the air, and the EFI system can spray more fuel to produce more power at these lower rpms
If you are replacing engine components with aftermarket upgrades, progressing from the filter to the intake valves, bolting on one of these Holley TBs is a logical step in that process. Likewise, if you already upgraded your engine with less restrictive components like an intake manifold and cylinder heads, then a Holley High-Flow EFI Throttle Body will release that pent up, power potential hiding within your engine.
 Here is an excellent shot...  Here is an excellent shot showing the end result of all Holley's CNC work. Every inch, from the dual 52mm (2x52mm) venturi bores to the butterfly valves, has been smoothed out to remove flow restrictions. |  The Holley TBs come with a...  The Holley TBs come with a completely new throttle spring assembly to keep opposing pressure against the throttle cable, leading to crisper throttle control. All factory throttle and kickdown cables fit the new throttle body. |  After removing the air intake,...  After removing the air intake, unbolt the factory throttle body and spacer with an 8mm nut driver. Unfortunately, the longer bolts provided with our aftermarket spacer will not fit the countersunk holes of the new Holley unit, so the spacer is getting ditched for now. |
 It is easy to see the quality...  It is easy to see the quality and meticulous design that differentiates the stock throttle body from the new Holley High-Flow unit. Notice the large metal lips that surround the stock TB's venturi bores, compared with the smooth curves leading directly into the Holley's 6061 aluminum bores. |  The stock throttle positions...  The stock throttle positions sensor (TPS) and the manifold absolute pressure (MAP)...... |  ......sensor are removed with...  ......sensor are removed with a T25 Torx Bit and bolt onto the new Holley TB, reusing factory hardware. |
 Once the sensors were on and...  Once the sensors were on and the idle air control (IAC) motor was swapped onto the rear of the TB, we threw a new gasket on the top of the intake manifold and bolted down the 2x52mm aluminum throttle body. We found it was easier to attach the throttle linkage before tightening down the bolts. |  How'd we like it? Again,...  How'd we like it?
Again, this throttle body is an improvement over stock because it no longer restricts potential power made by our other engine modifications. As expected, our relatively unmodified engine did not notice a change in fuel economy, and any power gained was likely only worth a few horsepower. However, the throttle response alone is what made the part worthwhile. The improvement in pedal-to-reaction time was significant, and it feels like our truck jumps off the line just a little bit faster. | |