Firebird Trans am 400 MOTOR VS. 455 MOTOR

Question

just by looking at it how can i know if the car has a a firebird 400 engine or a 455 engine

the numbers that the engine have ,do they help any

the motor is taken out and its in a junk yard

Answer 1

Pontiac 455s have 455 cast into the block on the side - easy to spot if out of a vehicle . It is located vertically at the Left front side of the block between the #1 cylinder and the front of the engine ahead of the starter where the frost plugs are (I just checked the one in my garage).

Externally all Pontiac engines appear identical whether it is a 301, 326, 350, 389, 400, 421 or 455 - there are no small block or big block pontiacs. heads, etc are mostly interchangeable, the mounts are the same, etc. You can't change or add casting #'s. If the heads are off  the bore is 4.15 inches.

Stamped numbers are located on the passenger side block deck - 455s have the following codes:WA, WC, WJ, WG, YA, YC, YG, YE, WD, WM, YB, YE, ZJ, Z8, XD, X8, W8, Y8, or WX depending on year and application.

I have a 1976 455 with 400 small chamber (Not small block!) 4X heads and a RA IV cam in a 3600 lb car. Runs 13.5s with a stock bottom end.

Good luck

Answer 2

the size of the valve covers the 455 are much wider than the sb400,also can take off one valve cover the valves are larger in the 455 than than 400..

Answer 3

400 vs 455, go with the answers with the thumps up! Thumbs down wrong info. you can check internet for Pontiac Engine Identification Codes. Find out if your engine is for a standard or automatic tranny, Standard tranny engines are ussually built stronger and should be used for automatics or standards, but an automatic tranny engine should be used for automatic tranny only. 400 great for strip, right feel, 455 quicker but sometimes you can lose some time to excessive wheel spin if you build them with 10:1 or (10:25) : 1 compression ratio.

Answer 4

KAM and ID are both wrong, sorry guys! The first guy is right the blocks have the #s cast into the side of the blocks. there will be large #s that stick out or are cast so that they are raised #s and will be either "455" or just "55" for a 455 and will be "400" or just "00" for a 400 and "350" or just "50" for a 350. It will be the same thing inside of the engine under the intake and valley pan. It is cast into the lifter valley the same way, but I don't recommend having them take those parts off to prove it cause you just have to look at the side of the engine.  

Answer 5

Where did those two yahoos come from?

There is absolutely ZERO difference, externally, in a 400, 455, or any other common Pontiac V-8. (428, 389, etc)

You can't tell one from the other just by opening the hood and looking at them.

As the first poster mentioned, the engine size is cast into the block.  

Both are great engines.   You can make lots of power with either.   Lots of aftermarket support.   Almost everything is interchangeable between the two.

Also, you can turn the 400 into a 455 if you want to.   Only difference is  .030" bore, stroke, and main bearing size.

So bore a standard 400 .030" over, get standard 455 pistons, take a 455 crank and have the mains machined to 400 size, and you have a 455 based on a 400 block.   Plus you get the more desirable, smaller main bearing size.  

But really this is mostly for racing purposes.

I had a 400 in my old 76 Trans Am, stock bottom end, 6x heads, Comp Cams 280 Magnum cam, stock intake, and it ran high 12's @101mph.   Best of 8.32 @85mph in the 1/8 mile.  

Answer 6

you can tell by the Block, is it a 455 Big block or a 400 small block ?my brother has a 1967 fire bird with a 455 big block wich is ALOT of power,don't go by the numbers because they can be changed,if your not sure ask the attendent at the yard  small block or big block!good luck i hope this helps.