1978 Pontiac 400 YA version. SMALL BLOCK OR BIG BLOCK??? - F-Body Online

tgfrench · 08-08-2008, 08:45 PM

I'm 15 and restoring a 78 trans am with original motor. Can anyone tell me is the 78 YA Pontiac 400 a big block or a small block.

Thanks
-Tom

82Firebird · 08-08-2008, 09:49 PM

I think its considerd a small block the bore for a Pontiac is 4.121''.

birddog · 09-15-2008, 09:49 PM

this may be a trick question, unlike chevy and ford
pontiac v8s 326 to 455 are the same size blocks.
the bore and stroke is changed to achive the differant CID.
So there are technically no small and big blocks.
anything over the 400 could be considered a "large
displacement" engine.

bigblock400 · 09-16-2008, 01:08 PM

Exactly. Block size didn't change... hence, my name is a play on that same scenario.

1956davis · 09-27-2008, 01:48 AM

Nice to hear from a 15 yr old who doesn't want a Honda or Toyota "Fast and Furious" car.

08-08-2008, 08:45 PM	#1
tgfrench New Member Location: Jersey Posts: 5 Trader Rating: (0)	1978 Pontiac 400 YA version. SMALL BLOCK OR BIG BLOCK??? I'm 15 and restoring a 78 trans am with original motor. Can anyone tell me is the 78 YA Pontiac 400 a big block or a small block. Thanks -Tom

08-08-2008, 09:49 PM	#2
82Firebird Member Location: Minnesota Posts: 195 Trader Rating: (0)	I think its considerd a small block the bore for a Pontiac is 4.121''. __________________ 1967 Chevy c/10 Custom - 283 with 3 on the tree 1982 Firebird "I'd rather push a Chevy then drive a ford"

09-15-2008, 09:49 PM	#3
birddog New Member Location: by GOD north carolina Posts: 2 Trader Rating: (0)	trick question this may be a trick question, unlike chevy and ford pontiac v8s 326 to 455 are the same size blocks. the bore and stroke is changed to achive the differant CID. So there are technically no small and big blocks. anything over the 400 could be considered a "large displacement" engine.

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09-16-2008, 01:08 PM	#4
bigblock400 New Member Location: Jax, fl. Posts: 13 Trader Rating: (0)	Exactly. Block size didn't change... hence, my name is a play on that same scenario.

09-27-2008, 01:48 AM	#5
1956davis New Member Location: Abilene, TX Posts: 7 Trader Rating: (0)	Nice to hear from a 15 yr old who doesn't want a Honda or Toyota "Fast and Furious" car.