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Two To Four Barrel Carb Swap - Jp Magazine

Christian Hazel Brand Manager, Four Wheeler

The AMC 360 V-8 in our ’78 Cherokee Chief had good low-end grunt, but ran out of lungs above 3,500 rpm. And although we like the off-road performance of the factory Motorcraft 2150 two-barrel, it was time to uncork our V-8 with some Edelbrock parts made right here in the USA. If we had a more aggressive camshaft, Edelbrock’s Performer RPM Air Gap manifold is the natural choice, but the standard Performer manifold (PN 2131) is the best fit for our dead-stock 360. Those needing to retain the EGR can order manifold PN 3731. We topped the Performer intake with Edelbrock’s Thunder AVS 650 cfm Off-Road carb with electric choke. To save some coin, we ordered a reconditioned model, PN 18269. The brand new carb is PN 1826.

amc V 8 Uncorked upgraded Amc V 8 Photo 43237920

We discovered the Thunder AVS carb bowls quickly ran dry once we cracked open the secondaries, so we swapped fuel pumps and ensured we had a solid 6.5 psi fuel pressure through the rpm range. The problem improved, but didn’t vanish, so we cracked open the carb and raised the floats. Again, the problem improved, but the carb still runs dry if you stay in the secondaries too long. We’ll have to swap in a higher-volume fuel pump to cure the issue. But until the carb drains dry, wow, what a difference. The engine pulls way stronger from the bottom all the way up to about 5,000 rpm where the cam falls on its face. It really is like pulling the cork out of a bottle. Our AMC is finally free to rev.

PhotosView Slideshow We ordered a bit more than we needed, ultimately using Edelbrock’s Performer manifold (PN 2131), reconditioned Thunder Series AVS 650 cfm Off-Road carb (PN 18269), 14-inch Signature Series air filter (PN 1223), L-shaped hard fuel line (PN 8126), and new intake bolts (PN 8534). Edelbrock makes its own AMC intake gaskets (PN 7213) which we didn’t use since they can’t be used with the factory-style valley pan gasket. It’s easy to swap intakes on an AMC V-8. Remove the distributor cap for clearance (you can even leave the wires hooked up), drain the coolant, remove the fuel line, and remove the carb and intake as a unit. Remove the factory valley pan gasket and completely clean the head and valley surfaces. Block off the intake ports and make sure no carbon or crud goes into the oil passages. There are two schools on using the factory-type valley pan or omitting it for Edelbrock’s PN 7213 intake manifold gaskets. The Edelbrock gaskets will conform to cylinder head surface irregularities better, but the stock-type valley pan gasket will keep hot oil off the bottom of the intake and further reduce the possibility of the PCV valve sucking oil. We bought a new valley gasket and coated both sides with Permatex Aviation Form-A-Gasket and ran a thick bead of Permatex Right Stuff gasket maker across the valley ends and around the water passages. The PCV valve is in the rear of the manifold above the cam and lifters where it can suck up hot oil. The factory devised this oil shield that’s riveted to the bottom of the stock intake manifold. You’ll want to drill out the rivets and transfer the shield to the Performer manifold. Otherwise, the PCV can pull oil into the intake charge resulting in low oil levels and possibly fouled plugs. The Edelbrock Performer manifold comes with the oil shield mounting holes already drilled in the proper locations and includes these solid rivets. Carefully tap them partially in and then use a drift to completely bottom the rivets against the manifold. It’s a secure press fit, but if you’re a worrier you can add a bit of red Loctite to ensure the rivets never go anywhere. Drop the manifold on and torque the bolts from center-out in two steps to 25 lb-ft. We made the stock two-barrel carb linkage work, but we really need to buy a longer throttle cable. The AVS carb allows easy adjustment of the secondary butterfly opening for quick tunability. Off-road the carb never stumbled or loaded up. We could idle the engine at angles and even shut down and restart with the nose pointed severely up- or downward.