[81blackhawk]

I recently bought an 81 Trans am non turbo. It cam with a 301. The motor is out of it. In the purchase I was givin, what I was told was a pontiac 350. I have a pontiac 455 out of a 1972 bonniville. I am leaning towards using the 455, but I do not know if i have to change out the motor mount on the cross member. Should I shop for a pontiac 400. I want it keep my accessories. Can anyone provide me a direction to preceed. Thanks

[mzbk2l]

81blackhawk, welcome to PY!

You may want to post this in the 77-81 Firebird and Trans Am forum on this same board; you'll attract more of the experts there.

Having said that, the Pontiac 350 and 455 share common dimensions, so the 455 will fit anywhere the 350 will fit, and it will use all of the same accessories. I have done that same swap before, and I believe it was a straight bolt-in. Been quite a few years, though, so I may be forgetting a few steps.

[bastard]

It seems like I remember hearing that the 301 uses the same mounts as the bigger engines. It is the same block design, just a shorter deck version of the larger displacement ones.

[81blackhawk]

Can anyone help me. I have played with mustangs and camaros, but this is the first Trans Am I have owned. I just purchased the car with the motor remove. The car came with a new with a 301, non turbo. In the purchase I received a Pontiac 350 in the deal, with 350 heads. My parents have a Pontiac 455 and tran out of a 72 bonniville with all the accessories. My question is which motor do I place in the car? Are the engine mounts the same? If I use the 455 will it interfer with the a/c box? Should I use the 350 for an easier fit and lighter wieght? thanks in advance for the help.

[frans455]

Id use the 455, with possibly the 350-heads (especially if the code on the center ports is 6X, then you get 2.11/1.66 valves - such as most smog-heads from the mid-late seventies). The 350-heads will get you higher compression ratio due to smaller combustion chambers.
Pontiac 350-455 is same dimension. 301 is a low-deck Pontiac-block - the motor mounts should fit on the 350-455 also.

[2manyT/A'S]

The 455 will fit & work just fine & you will likely be reasonably happy with the engines power output in stock form,providing it IS a 4bbl.
As frans455 states,the small chamber 6X heads are a good upgrade with the addition of a Ram Air cam.

You will need to used the accessory mounting brackets (alt. & P/S) from a Bird,as the ones from the Bonneville won't let you close the hood on your bird.

If your 81 originally came with a 301,just use the original mounts & engine mount brackets & bolt it in. Exhaust pipes will need to be modified.

There is not a TON of weight difference between the 350 & 455,but 301 (non-turbo) is definately lighter.