Barn-Find 409 Engine Rebuild - Unearthing A Legend, Part 3

Our barn-find 409 gets buttoned up and hits the dyno.

Tommy Lee Byrd Jun 27, 2014 0 Comment(s)
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If you’ve followed along with our 409 build (June, July ’07), you’ve seen a forgotten W-motor get a new lease on life. The engine’s mysterious past and flawless short-block encouraged us to retain the rotating assembly, and update the top end of the engine, as well as the valvetrain. So far, the progress has been smooth and steady, with few hiccups along the way.

Without question, a 409 engine build has some peculiar details, and we hope we’ve covered most of them in parts 1 and 2 to prevent any hard times if you plan to tackle a similar project. This month, we’re putting the finishing touches on the 409, and putting it through the wringer on the dyno.

To button up this W-motor, we opted for dual quads, because it only seems natural on a high-performance 409. We used Edelbrock’s Performer RPM large-port intake manifold and a pair of Edelbrock Thunder Series (1803 and 1804) carburetors. Coming in at 500 cfm each, the dual four-barrels provide plenty of fuel for the thirsty 409, which utilizes a 110-gallon-per-hour mechanical fuel pump.

During the finishing stages of the build, we also install a Pertronix Flame-Thrower “Plug N Play” billet distributor, which is an easy solution for updating the engine to electronic ignition. The small-body distributor doesn’t take away from the old-school looks of our 409, but the electronic module certainly outperforms the original points-style ignition system. One of the cool features of the Pertronix distributor is a built-in rev limiter, which will be set to 6,000 rpm to keep our engine alive and well. We also used a Pertronix Flame-Thrower III coil and a set of Pertronix 8mm plug wires. Edelbrock suggests RC12YC spark plugs for use in its Performer RPM cylinder heads, so that’s exactly what we used.

409 Engine Rebuild Edelbrock Pertronix 2/20

It seemed fitting to give our 409 the dual quad treatment, so we used an Edelbrock setup consisting of a Performer RPM intake manifold and dual Thunder Series 500-cfm carburetors. The finned aluminum air cleaner is an old-school touch.

Once all of the vital details were completed, we finished off the engine with Edelbrock Classic Series finned aluminum accessories in the new satin finish, for the raw, as-cast look. An Edelbrock aluminum water pump keeps the engine cool, at half the weight of the original cast-iron pump.

The final, and most intimidating, step of the entire build was the dyno session. Taking a brand-new engine and putting it through its paces can be unnerving, especially when you consider the volatile nature of the 409. It’s a short stroke engine that really wants to rev, but the heavy pistons can wreak havoc if the connecting rods aren’t up to the task. So we kept the engine below 6,000 rpm on the dyno to prevent carnage.

The end results were very pleasing, as the 409 screamed to its peak horsepower figures at 5,800 rpm. It cranked out 504.8 hp at 5,800 rpm and 515.3 lb-ft of torque at 4,500 rpm on the dyno at Hixson Motorsports in Soddy Daisy, Tennessee. Hixson Motorsports builds cars for the ARCA racing series, so owner Wayne Hixson was very particular about the dyno setup. He provided the fuel (Sunoco 260 GTX), as any traces of other fuel in one of his engines could result in a fine or disqualification. With an octane level of around 100, the racing fuel allowed us to get a little more aggressive with our ignition timing, and we also had the advantage of Hixson’s fresh air duct, which replicates the cowl pressure experienced when one of his racecars is at speed. Our dyno pulls were a maximum effort for our combination, but we can expect this engine to make around 470 hp on pump gas and a standard timing tune-up of 34 degrees.

Originally, this 409 would’ve been rated at 425 hp, so we made substantial gains without any fancy machine work or exotic parts. We simply bolted a fresh top end onto a mostly stock bottom end, and added a hydraulic roller camshaft and an upgraded ignition system. We also need to give some credit to the exhaust, as we ditched the original manifolds in favor of Hooker Super Comp full-length headers (PN 2171HKR). With 17/8-inch primary tubes and 3-inch collectors, the headers let the 409 breathe easily, and it sang quite a tune at 5,800 rpm.

With the engine and testing complete, it makes for a great story when you consider these components went through this same sort of abuse in a drag car 50 years ago. The fact that the old engine can still scream after all those years of neglect is part of the cool factor of our mysterious barn-find 409, but it wouldn’t be possible without the companies that do the research and make these updates simple and effective. And while many 409 builders would’ve abandoned the original parts and given this engine the stroker treatment in an effort to make more horsepower, we’re happy with our 505 horses, and happy it survived the dyno thrash session. Now this 409 is ready for the street or the track. The real question is, what are we going to put it in?

409 Engine Rebuild Rivets 3/20

1. Before we install the intake manifold, we must first install the baffle, which is included in the kit. This baffle is held in place with three rivets, which are hammered into three bosses in the intake. The rivets are a tight fit, but it doesn’t hurt to use a few drops of red Loctite for extra assurance.

409 Engine Rebuild High Temp Silicone 4/20

2. Edelbrock offers high-performance intake gaskets but suggests using a bead of high-temperature silicone on the front and rear surfaces where the intake meets the block.

409 Engine Rebuild Performer Rpm Intake 5/20

3. After allowing the silicone to tack up, the Performer RPM dual-quad intake was lowered into place. We tried our best to align the boltholes without disturbing the silicone in the process.

409 Engine Rebuild Arp Thread Sealer 6/20

4. Once again, we’re dealing with wet boltholes, so we used ARP thread sealer on all of the intake bolts just to be safe. The intake is held in place with 16 stainless steel ARP fasteners.

409 Engine Rebuild Tighten Intake Manifold 7/20

5. Starting in the middle, and working our way out in a clockwise pattern, we tighten the intake manifold. After all of the bolts are snugged down, we tighten the bolts to 30 lb-ft of torque.

409 Engine Rebuild Pertronix Flame Thrower Billet Distributor 8/20

6. Now we can drop in the Pertronix Flame-Thrower billet distributor, which features an Ignitor III module. Out of the box, this distributor is set up to provide 24 degrees of timing by 3,500 rpm, so setting our initial timing at 10 degrees (resulting in 34 degrees total timing) is a good place to start tuning.

409 Engine Rebuild Adjust Valves 9/20

7. With the engine still on top dead center on the number one piston, we can begin adjusting the valves. For this setup, we adjusted to zero lash (when we could no longer spin the pushrod) and then made another half turn.

409 Engine Rebuild Mechanical Fuel Pump 10/20

8. Other small pieces of the puzzle can now go together, such as the mechanical fuel pump, rated at 110 gallons per hour.

409 Engine Rebuild Thunder Series Carb 11/20

9. The Thunder Series carburetors go on next, and they slide over the stud kit we picked up from Edelbrock. For this dual quad setup, one carburetor features an electric choke, while the other is a standard manual choke model. Both are rated at 500 cfm.

409 Engine Rebuild Linkage 12/20

10. Dual-quad linkage can sometimes be tricky, but Edelbrock makes it simple with this adjustable linkage setup. It can be used as direct linkage or progressive linkage, and you can adjust how quickly the secondary carburetor comes in.

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