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289ci Four-Barrel Intake and Carb Swap - Breathe In, Ride Out
We Add 32 rwhp and a Ton of Fun With a Simple Four-Barrel Intake and Carb Swap
It sounds like an old cliché by now, right? Just do a four-barrel intake and carb swap, and wake up your old, lazy 289ci sloth. But it can’t be quite that simple, can it? Turns out that it may be just that simple. Sure, a cylinder head swap, stroker kit, or power-adder could give you a bigger power boost, but those are big (and expensive) projects. We’re talking about taking a basically stock 289 to the next level relatively inexpensively. This kind of swap will not break the bank, and you can do it yourself, in your driveway, in just a few hours.
At the heart of a swap like this is the intake manifold—the most difficult part of the job. But with basic handtools and fundamental mechanical skills, just about anyone can swap it themselves. The key is to make sure you have everything you need before starting. You’ll need intake manifold gaskets and RTV sealant if you want to keep it as simple and cheap as possible.
While you’re at it, though, this is a great opportunity to replace things like radiator hoses, heater hoses, hose clamps, thermostat, thermostat housing, vacuum hoses, and coolant temp sensor. And since the coolant system needs to be drained, it’s also a good time to flush the gunk out of your radiator and add fresh coolant. To us, opting to do these things is a no-brainer.
Our test subject, a ’65 coupe owned by Frank Cossota, is a 289ci four-speed survivor from California. It appears to be stock, with a stock intake, stock-looking heads, and stock-style carburetor. Frank found a receipt for a 289 rebuild in all the paperwork he got with the purchase, which he made recently. The receipt was dated 1998, with “The Beast” in the description. We doubted that to be accurate. Sarcasm, maybe?
There’s only one way to find out, so we drove the coupe to AntiVenom in Seffner, Florida. AntiVenom has a Dynojet chassis dyno, and allowed us to do our before and after testing there. The results? Well, power peaked at 132 rwhp and torque at 226 lb-ft. That’s about 165 flywheel horsepower, assuming a 20-percent drivetrain loss. Not bad, but certainly not a “Beast.” We could only assume that the heads and cam are stock as well.
Back at our SIM Tech Center, shop sage Darrell Kunda handled the install. Our intake manifold of choice is the Weiand Street Warrior (PN 8124; $156.95). This dual-plane aluminum intake is designed specifically for mild to moderate street engines, and features a powerband from idle to 5,500 rpm—ideal for our little 289. To top it off, we chose a 625-cfm Street Demon (PN 1901; $391.95). This new integrated design from Demon features an electric choke, single fuel inlet for ease of install, and is ready to run—no tuning necessary.
After Kunda removed the stock pieces and began cleaning the mounting surfaces, we weighed both intake manifolds. Not surprisingly, the stock piece tipped the scale at 38 pounds, and the Weiand piece weighed in at 15.5 pounds—a 22.5-pound savings. That doesn’t sound like much, but you’ll appreciate the weight savings as you install the aluminum piece. It’s like the difference between a full-grown Staffordshire Bull Terrier and a Miniature Schnauzer.
Installation was a breeze, and we went ahead and took care of those aforementioned items while we were at it. Our testdrive indicated a significant improvement, but the real results would be on the dyno. Back at AntiVenom, we spun the rollers again, yielding 164 rwhp and 245 lb-ft of torque. The peak-to-peak improvement was 32 horsepower, which alone is impressive enough. But the under-the-curve improvement was huge in torque production—as much as a 40 lb-ft difference (at 3,800 rpm), even though peak-to-peak shows “only” a 19 lb-ft improvement.
Driving on the street is much improved, transforming an anemic heap into a fun-to-drive cruiser. It retains its mild demeanor at part throttle, but wakes up in an instant when asked. And we didn’t even do any tuning—we just bolted the parts on right out of the box. That certainly put a smile on our faces.
Problem is, our powerband ends somewhere between 4,000 and 4,500 rpm. The solution, we say, would be a pair of nice aluminum heads and a mild camshaft. Those should boost horsepower to over 200 and torque to around 275 and bring the top of the powerband to 5,500 rpm. It will probably be a while before Frank grows tired of this setup and needs more power to make him smile, but we’ll report the results to you if we can talk him into it.
1. This Californian survivor features a 289ci stocker and a four-speed transmission. Though refreshed some time ago, the powerplant looked mostly stock, down to the stock intake and carb. We needed to do something about that.
2. Designed as an entry-level V-8, the 289ci two-barrel C-code certainly left performance on the table, which was the job of the K-code four-barrel.
3. Tech Center Manager Darrell Kunda began by removing the fuel line, throttle linkage, and mounting hardware from the stock two-barrel.
4. Kunda removed the carburetor.
5. He then unbolted and removed the stock intake manifold.
6. Sixteen years of crud was built up in the coolant passages, so we took this opportunity to clean out what we could reach.
7. To solve the problem of anemia with Frank’s ’65 coupe, we chose a simple four-barrel swap. We chose Weiand’s Street Warrior aluminum intake manifold (PN 8124; $156.95). It has a powerband from idle to 5,500 rpm, and is an ideal upgrade for a stock 289.
8. Demon has an all-new line of Street Demon carburetors. We chose the smallest, a 625-cfm version (PN 1901; $391.95) with the polymer body. An all-aluminum version (PN 1900) is only $329.95.
9. We also ordered up this installation kit (PN 160049; $17.99), which is a must.
10. Side by side, our new Weiand four-barrel and the stock iron two-barrel intake.
11. Other than the obvious differences seen here, there’s a huge savings in weight. The stock intake weighs 38 pounds, and the aluminum Weiand only weighs 15.5 pounds—a 22.5-pound savings.
12. Kunda prepped and cleaned all of the intake mating surfaces and soaked up what little coolant dripped into the valley when he removed the stock intake.
13. He then began prepping the intake for installation. It comes with pipe plugs for unused ports, which Darrell installed after a coat of Permatex thread sealer.
14. He then installed a new heater pipe.
15. Here’s the intake ready for installation with new heater pipe, coolant temp sensor, and pipe plugs.
16. We went ahead and restored the water neck by sandblasting and painting it, and then installed it with a new thermostat and gasket.
17. We went with Fel-Pro intake gaskets, slightly larger than stock.
18. Kunda installed the gaskets, and then laid a thick bead of Permatex Ultra Black along the front and rear bridges.
19. He then dropped the intake into place.
20. Earlier, he cleaned up the stock intake manifold bolts and painted the heads to prevent them from rusting.
21. He installed the bolts and torqued them to 14 to 16 ft-lb.
22. The Goggle Valve Secondary (GVS) on the Street Demon delivers twice the airflow of the primaries, which allows improved fuel economy at cruise and mild driving, but up to 625 cfm at wide-open.
23. Installed, the Street Demon is quite handsome. No, it doesn’t look like a traditional carb, and that’s because it isn’t.
24. We also took this opportunity to replace the radiator hoses, heater hoses, and clamps.
25. After everything was tightened up and the coolant was topped off, Kunda fired it up and adjusted the idle. This was the only adjustment we had to make. The hardest time we had was with adjusting the stock throttle linkage, which has seen better days. If your ’Stang is all original like Frank’s, you might want to look into replacing it as well.
26. After a short testdrive, we headed to AntiVenom to re-dyno the little orange coupe on the Dynojet.
27. We picked up both power and torque throughout the entire rpm range. Power output was up from 132 rwhp to 164 rwhp. Torque production, though, is way up. Though peak torque production is up from 226 lb-ft to 245 lb-ft (a 19 lb-ft difference), torque production is up by 40 lb-ft throughout most of the midrange. It’s out of gas by 4,500 rpm, so it’s begging for a head/cam swap. Frank’s probably going to be perfectly happy with the improvement, though, so we’ll just have to keep bugging him until he caves.