a 1968–1972 BOP (Buick, Olds, Pontiac) to work with the standard LS conversion mounts is handled one of two ways: convert to Chevy small-block frame stands or use LS-specific frame stands.
The early 1964–1967 A-Body cars are more difficult because these were not designed to accept all engine makes. A Buick used Buick mounts, a GTO/LeMans used Pontiac mounts, and so forth. A couple of aftermarket solutions do not require welding: Hooker (Holley) and BRP Hot Rods adapter mounts. They use existing holes in the frame to adapt the chassis to accept an LS engine mount. The Hooker mounts use the fourth-gen Camaro LS motor mounts, and the BRP mounts use a proprietary polyurethane mount. Conversion mounts that adapt non-Chevrolet A-Body frames to accept a Chevy small-block mount are readily available through companies such as Original Parts Group.
When adapter manufacturers talk about “stock location,” it is important to recognize that this refers to the original engine-to-transmission mating surface plane. LS engines are 1 inch shorter than a traditional Chevy small-block. Therefore, they do not have offset cylinders, and this means that the rear of the block is shorter than the Gen I block. Adapters that position an LS in the “stock location” place the transmission mating surface in the same location it would be if a Gen I Chevy small-block were installed in the vehicle.
Chevy Adapter Mounts for the A-Body
Most adapter mounts are designed to work with the standard Chevy small-block three-bolt engine mount. For the A-Body, three different versions of motor mounts are offered: clamshell tall/narrow (early style), and short/wide.
Clamshell Mounts
The clamshell type is more common on later GM vehicles, but can be found on 1964–1972s. These use a stamped steel pod that bolts to the engine with a steel and rubber mount that bolts to the frame. These can be used with most adapter mounts.
Tall/narrow, short/wide, and clamshell are the three main types of motor mount that have been used for the typical Chevy small-block frame stands. The clamshells are completely different from the other types. The tall/narrow mounts (left) are used for 350s and big-blocks. The short/wide mounts (right) are used on 307 cars. They both bolt to the engine, but wreak havoc on your engine position and install.
Tall/Narrow Mounts
These are the most common in Chevrolet A-Bodies. The tall/narrow distinction is confusing, however, as the frame pad is called short/narrow. Tall/narrow refers to the engine-mounted component. These Chevy small-block mounts from a small-block 350 were adapted to the big-block 396/454 engines in Chevrolet A-Body cars.
There is about a 1/4-inch difference in overall height between the tall/narrow (left) and the short/wide (right) versions, but it’s not enough to allow some other components to fit. In addition, the narrow mounts don’t sit down on wide 307 frame stands.
The center of the engine mounts measures 2⅜ inches between the mounting ears and 2
These frame stands are readily available in the aftermarket as reproductions.
Most LS engine adapters position the engine closer to the radiator, which is fine, because most of them do not run mechanical fans.
Short/Wide Mounts
Chevrolet used a different set of frame stands for the 307 than the 350 engine when installed in A-Body cars. The 307 frame stands are 1/2 inch taller than frame stands for the 350 engine. The width of the pad (where the two mounts come together) is also different. The 307 mounts are wider and measure 2⅝ inches on both the frame stand and the engine block mount. However, the block mount measures 1¾ inch tall and therefore is shorter than the 350 version.
These are the most commonly sold mounts at the parts store, so it pays to know the difference.
The type of mount you need depends on your vehicle and the accessory drive and oil pan you use. That being said, the best solution is to use the 350 version. These raise the engine a little higher than the 307, which provides better clearance for the oil pan and steering linkage. In most cases, you still need to raise the engine a little more to clear the steering linkage. About 1/2 inch usually works, depending on your oil pan and the angle of the engine/transmission. Most adapter plates require the 350 version.
Most A-Body cars have an interference issue with the inner tie-rod ends. The Mast oil pan for A-Body swaps has the best clearance, but you may need to raise the engine to get adequate clearance. The Hooker kit (shown) and similar kits have complementary parts that work as a complete system, and include mounts, pan, and headers.
Even with the right parts, some inner tie-rods are simply larger than others, which could result in light scrubbing, such as this on the bottom of the pan. This occurs at the extreme end of the turn radius.
With the mounts on the block, the engine can be lowered into the car for a test fit. It is a good idea to test fit your engine before finalizing the details.
Energy Suspension’s correct tall/narrow mounts provide adequate clearance using the Trans-dapt adapters and Mast oil pan. The inner tie-rods just barely touch at full lock.
For the 1969 Chevelle project featured in this book, the 350 mounts were used with a set of Energy Suspension 31117G motor mounts and a Mast oil pan. The driver-side inner tie-rod cleared, but the passenger’s side hit the pan. I raised the engine with an additional spacer block between the engine and the mount, which allowed everything to clear. The Energy Suspension mounts come with one spacer; I used two.
Hooker offers another LS swap solution for A-Body vehicles, particularly for non-Chevrolet brands that don’t have factory Chevy small-block frame stands. Instead of searching for Chevy small-block stands, you can use these pieces along with a fourth-generation Camaro LS motor mount to place the engine in the correct position. These are available in both “stock” position and in the 2-inch-forward position.
Using
