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75-81 F-Body Firebird/TA
Pontiac V8 75-81 F-Body Firebird/TA
Late Second-Gen — 75-81 F-Body Firebird/TA for Pontiac V8s
The 1975-81 Firebird and Trans Am uses a mount system of its own, and it is the chassis most likely to be running an engine it did not leave the factory with. Late second-generation cars take a specific frame mount, and putting a 1961-1979 326-455 in one usually means an engine mount adaptor between the block and that frame mount.
Butler builds the F10774 engine mount adaptor for exactly this job and offers it bundled with rubber, billet polyurethane or solid frame mounts. Butler also stocks the frame mounts separately, along with 3/16" frame mount spacers and a Warpath Restoration adapter kit.
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1. The Engine Mount Adaptor Is the Center of This Page
Most 75-81 Firebirds on the road have had an engine change, and the block that went in rarely has the same mount pattern as the one that came out.
| Butler F10774 engine mount adaptor | puts a 1961-1979 326-455 into a 1975-81 F-body. It replaces the factory engine mount for the 75-81 car, and the extra bolt holes adapt a 61-69 two-bolt block for use in a 70-81 F-body. Black powder coat, and the kit includes the 7/16" bolts and locknuts. |
| Excludes the 403 | Butler's adaptor kits are for the Pontiac V8 and specifically exclude the Olds 403. Note that the 75-81 frame mounts themselves are cataloged for Pontiac V8 and Olds 403, so do not assume one exclusion covers both parts. |
| Expect to fit, not just bolt | Butler's own note says these may require some modification or slight shifting of frame mounts for proper alignment, both because of the thickness of the required adapter and because of tweaks in the frame from years of use and damage. Plan on trial fitting before you torque anything down. |
2. Picking the Frame Mount: Rubber, Billet Poly or Solid
Butler sells the F10774 adaptor bundled with each of the three, or you can buy the frame mount by itself if your adaptor is already in the car.
| Stock replacement rubber | a direct factory replacement frame mount for the 75-81 car, cataloged for Pontiac V8 and Olds 403. This is the choice for a driver or a correct restoration, where you want the factory isolation back and nothing more. |
| Billet CNC polyurethane | milled from 6061 billet aluminum with custom molded poly inserts and billet sleeves, rated to 650+ horsepower. Butler describes it as much stronger and more stable than the factory mount, and it prevents excess engine movement and the damage that movement does to other components. Original engine height is not altered. It fits original OEM engine mounts as well as the Butler F10774, though you may need to cut the end tabs off a stock steel engine mount. |
| Solid frame mounts | a direct factory replacement for 75-81 cars with a 400 or 455, black powder coated, working with stock steel engine mounts. Nothing holds the engine more precisely, and nothing transmits more vibration into the car. On a street Trans Am you will hear and feel every bit of it, which is why solid belongs in a car built to race. Butler notes these will work on a 70-74 car but you will have to drill the frame mount holes. |
3. Frame Mount Spacers and Heat
| 3/16" frame mount spacers | sold in pairs for 75-81 F-bodies, usable with either the replacement rubber mount or the billet poly mount. Mounts are not included. These are the shim when the stack-up is close but not right. |
| Keep heat off the poly | Butler is direct about this one. If you are running headers, ceramic coated headers are highly recommended, along with a heat shield or header wrap, because excessive heat may cause the polyurethane to melt or deteriorate. It is the most common way a good poly mount gets ruined. |
| Header clearance on adapter kits | the Warpath Restoration adapter kit that takes a 1965-69 two-bolt block into a 1975-81 F-body is noted to possibly interfere with some headers, and some 389 and 428 blocks may have to be clearanced. |
4. Ordering It in the Right Order
Work from the block outward. Count the engine mount bolt holes on your block first, decide whether you need the F10774 adaptor, then pick the frame mount by how the car is used rather than by what it is rated for. Buy the spacers only after you have the engine sitting in the car and can see what the stack-up actually needs.
Not sure what your Pontiac needs?
Call our tech team at 866-762-7527. Tell us your engine, heads, car, and power goal, and we will put the parts together as one combination that works.