1965 Ford Mustang GT - How-To Plan For Ponies: Part Three In A Five-Part Series
Making More Power With Hedman Hedders And A Turbo Exhaust System From National Parts Depot
From the December, 2000 issue of Mustang Monthly
By Jim Smart
Photography by Jim Smart
To bring you up to date, our...
To bring you up to date, our 289 4V engine was dyno-tested and super-tuned in stock condition in Part 1, then upgraded with an Edelbrock Performer RPM manifold and 600-cfm carburetor in Part 2. The total gain was a modest increase in horsepower and torque. This taught us something about packaging.
Parts 1 and 2 of our "Plan For Ponies" series, we've shown you what changes in induction and ignition do for performance. In Part 1, we removed the air cleaner, changed spark plugs, adjusted the timing, and installed a Pertronix Ignitor--gaining 4 hp and 5 lb-ft of torque. This demonstrated what simple engine-tuning could do. In Part 2, we gained a modest amount of power--installing an Edelbrock Performer RPM intake manifold, a 600-cfm carburetor, and a Pertronix Ignitor module.
This month, West Coast Classic Mustang of Reseda, California, will install Hedman long-tube headers. Magic Muffler of nearby Canoga Park will install a high-performance turbo 2-1/4-inch dual exhaust system from National Parts Depot. Then we're going back to Mike Morgan Motorsports to take another crack at the big drum to see what induction, ignition, and exhaust tuning has done for our Mustang.
1 Packaging should always...
1 Packaging should always be a balance of components that work well together. Installing only a high-performance intake manifold and carburetor without close attention to the exhaust system, heads, and camshaft won't net the power gains you're hoping for. Always plan for power with the correct combination of parts.
What we've learned most from this series is that you must plan for power as a package. And it's a good idea to begin with the exhaust system, not the induction and ignition as we have. We say this because we're convinced that our stock, original Mustang GT dual exhaust system has hindered our efforts. In order for an engine to perform, it has to have good exhaust scavenging; otherwise, no amount of induction, ignition, or headwork will matter.
Our high-performance Turbo 2-1/4-inch exhaust system from National Parts Depot has 2-1/4-inch pipes with Turbo mufflers that not only improve sound, but performance as well. Hedman long-tube headers reduce backpressure and scavenge exhaust gasses, while keeping torque in play. With aftermarket headers and larger exhaust tubing, we wonder what all this will do for performance. We're about to find out.
We took the Mustang back to Mike Morgan Motorsports, and once again, we were disappointed with the result on the first pull. Our rejetted Edelbrock 600-cfm carburetor struggled with an ugly flat spot that was hurting torque something awful. During throttle tip-in, the 289 was gasping for a respectable air/fuel mixture that would allow it to make power. Wide-open throttle passes were made with poor results. This was no reflection on the exhaust system or Edelbrock induction system; it was an issue of proper engine tuning. We did some carburetor tuning and achieved impressive results.
Prior to Run No. 2, we adjusted the Edelbrock carburetor's accelerator pump rod to see if we could eliminate the flat spot. We were marginally successful. The flat spot remained, indicating the need for more extensive carburetor tuning. Despite the surging, we gained 2.3 hp and 5.2 lb-ft of torque. This is due mostly to a warmer engine, not necessarily the accelerator pump adjustment. But this shows us what's possible, given respectable engine tuning.
Using Edelbrock's carburetor jetting kit, we tuned the main metering circuit using the pink metering rod spring. This gave us a richer fuel mixture where we needed it most: under power where an engine makes torque. This netted 5 more horsepower and 6.2 additional lb-ft of torque; not bad considering how easy this performance-tuning trick is.
2 Hedman Hedders has supplied...
2 Hedman Hedders has supplied us with a Jet Hot-coated set of long-tube headers for our 289.
They're easy to Install and...
They're easy to Install and include an adapter that moves the power steering cylinder away from the hot tubes.
3 This high-performance Turbo...
3 This high-performance Turbo 2-1/4-inch dual exhaust system from National Parts Depot includes a prebent, custom-fit, 2-1/4-inch H-pipe; exhaust; tailpipes; and a duo of Turbo mufflers. This quiet exhaust system is designed to improve flow while keeping all-important backpressure.
Run No. 4 gained us 1.8 hp and lost us 2.1 lb-ft of torque with a spring swap. Softer metering rod springs allow the fuel to activate sooner to virtually eliminate the flat spot. Horsepower is up marginally while torque remained nearly the same. The loss in torque can be attributed to a warmer engine, not necessarily the spring swap.
Just for fun, we decided to uncork the headers to see if there really is a difference in power without the restriction of an exhaust system. We gained an eye-opening 9.2 hp by simply opening the headers. But check out the torque. We lost 2.5 lb-ft of torque. Why? Because the exhaust system helps the engine make torque via backpressure, which--given the right cam profile--increases cylinder pressure. Horsepower nearly always increases when we uncap the headers. Torque almost always decreases. Derek Real of Mike Morgan Motorsports tells Mustang Monthly that torque would improve with a 2-1/2- or 3-inch diameter exhaust system.
Our latest battery of dyno tests demonstrate that a lot of power gains aren't always in the components, but in the tuning. Common sense carburetor tuning by Mike Morgan Motorsports has netted the greatest gains thus far. But these power gains wouldn't have been possible without the correct combination of performance parts from Edelbrock, Hedman, and National Parts Depot. This is where "package" thinking comes in. Think package. Think tuning. Then retune.
Next month, we're going to install a set of Edelbrock Performer RPM heads with larger valves and ports to see what kind of power gains can be achieved.
4 Jerry Choate...
...of West Coast Classic ...
...of West Coast Classic Mustang...
...removes the factory......
...removes the factory...
...cast-iron exhaust mani...
...cast-iron exhaust manifolds...
...common to 289 2V/4V en...
...common to 289 2V/4V engines.
5 Choate's '65 Mustang GT...
5 Choate's '65 Mustang GT has the original factory dual exhaust system, thanks to a dry California climate; however, even a dry climate catches up. Rust has taken a toll, making it necessary to cut off the old exhaust system.
6 Hedman offers installers...
6 Hedman offers installers a bracket that lowers the power steering cylinder to clear the header tubes.
This bracket installs in a...
This bracket installs in a matter of minutes.
7 New Hedman long-tube headers...
7 New Hedman long-tube headers are installed and bolted into place. For Choate, it was a simple task. Installing the left-hand header (driver side) mandates jacking the engine to the right to allow access from underneath.
Simply unbolt the engine mount...
Simply unbolt the engine mount and jack the engine. Install the header and reinstall the engine mount; it's that easy. The right-hand side is simple and installs from underneath.
8 Hedman headers clear the...
8 Hedman headers clear the undercarriage nicely.
|Dyno Run No. 1||Dyno Run No. 2|
|Hedman Headers with National Parts Depot's Turbo 2-1/4-inch Exhaust System||Accelerator pump rod adjustment for a stronger shot|
|Dyno Run No. 3||Dyno Run No. 4|
|Metering rod spring change (yellow to pink spring--softer)||Metering rod spring change (pink to silver--softer yet)|
|Dyno Run No. 5|
|With open headers|
9 Magic Muffler in Canoga...
9 Magic Muffler in Canoga Park, California, installs the NPD high-performance dual exhaust system.
Because the NPD system is...
Because the NPD system is designed for Shelby tri-Y headers, the collectors did not fit our Hedman units.
The NPD collectors were cut...
The NPD collectors were cut off the H-pipe...
...and Hedman collectors were...
...and Hedman collectors were welded in their place--otherwise, a perfect fit.
10 The NPD Turbo 2-1/4-inch...
10 The NPD Turbo 2-1/4-inch dual exhaust system fits snugly due to increased pipe diameter.
But it does a nice job and...
But it does a nice job and makes a throaty sound.