My friend has a 69 pontac Lemans with 455 big block bored to a 460. This kid i have been arguing with says that pontac didnt make big blocks.

This is his words exactly-
"Daltons right, if you would do your research next time, pontiac used a uni-block platform for all of their production v-8's, a 301 and a 455 used the exact same block, they just have different size cylinders. Also, they would almost be a medium sized block as they are bigger than a SB Chevy, but smaller than a BB (like a 454). And how did you get a 460 Pontiac anyhow, last i checked a 460 was a dodge engine, which would render this whole argument irrelevant, as you are apparently as dumb as the people who think that stickers add horsepower!"

So, can someone help me make sense of this argument. Did pontiac have both small and big blocks??

 

Pontiac V8's are basically all of the same engine family. Many parts interchange, but plenty do not. You cannot turn a 301 into a 455, for example. The 301 is a derivative that uses unique heads, etc. Thanks, oldtimer.

 

All Pontiac V8 blocks have the same bore spacing; they use the same cam, the same heads will bolt up, etc.

The 301 is a "short deck" block. Everything else about it is the same (dimensions that is), just, the deck is closer to the crank.

Yes Pontiac did have a 455. Their V8s have been available in 370, 389, 420, 428, 326, 400, 350, 455, and 301 (in roughly chronological order), that I can recall off the top of my head. I might have missed one, maybe someone else will fill in if so.

The usual definition of "small block" vs "big block" is most clearly delineated by the bore spacing. So for example, all Chevy small blocks have the same bore spacing (265, 283, 327, 302, 350, 307, 400, 262.5, 305, 267); and each of the various big block families has its own bore spacing (348, 409; and 396, 427, 402, 366, 454, 502 etc.) Same with Brand F; 302 & 351, as compared to the FE block (displacements too numerous to be bothered with) and their later "big block" 429 & 460. Chrysler had families the same way. Although I've never heard of a 460 Chrysler; only 460 F*rd.

Pontiac blocks are ALL the same bore spacing, so in the strict traditional sense, there are no "big block" and "small block" ones. Only, "standard deck" for all except the 301, which is a "short deck".

 

i think the one your missing is a 350. I know someone that has one bored to a 355 in a 65 GTO. im Not sure though.

 

Where did he miss it

 

The one that he is missing is based on the 301 low deck block it is around 260 something cubic inches.

 

sorry didnt see that! So, there is no big blocks and small blocks,there based upon deck height??

 

In a nut shell I suppose so, but there are definanely big and small blocks.

 

if all the bore sizes are all the same in pontac blocks,, then how do you differentiate a 455 with a 350 pontac block? Is it all in the heads?? Crank size perhaps?

 

What distinguishes a small block from a big block is bore spacing and that's all. You can have a 434 SBC and a 396 BBC but they're not the same engine.

Since Pontiac uses the same bore spacing on their blocks, they don't have a big/small designation.

Tall/short deck blocks is the distance from the crank centerline to the deck of the block. BBC have 2 common deck heights but they're both still a BBC. Many other type of engines offer the same block but with different deck heights.

The one exception to the bore spacing rule is for the super BBC blocks. Although they're all based off the BBC design, there are blocks available with a 5" bore space and even a 5.300" bore space is available. These blocks also have taller decks to produce engines up to and over 800 CID.

Sofakingdom pretty well covered it all. Although Pontiac doesn't have a small/big block. Chev and Buick do and I think Oldsmobile also does.

 

no, bore SPACING is the same. ie, hole 1 to hole 2 is the same gap apart. The hole is bigger on a 455 though. So yes, bore, and stroke is different from 350 to 455, and no, you can't just bore one bigger. Same reason why you can't bore a 305 to a 350, in spite of the equal bore spacing.

capisce?

 

THE MASTER HAS SPOKEN

 

hmm, I wonder how many posts it takes to go from "senior member" to "master"? Or heck, i'd even settle for moderator

 

I will start the campaign, "SONIX FOR TGO PRES, OR MOD, OR SOMETHING"

 

it's not all it's cracked up to be, the pay and the respect level are both pretty low and any dumbass can do it.

 

Missing are the 265 and 421 (not 420).

 

What the heck, were you demoted??

 

Thanks madmax!

You know what they say about memory when you get old; it's the second thing you lose. Trouble is, I can't seem to remember what the first one was. Although one of the girls at work told me once that I should ask my wife, she'd probably remember.

 

could of sworn there was a few other things that bastard 301 had different vs other pontiac motors? I honestly don't remember though it has been too long since I hjave worked on one
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same way as you tell a 283, 302, 307, 327, 350, and 400 apart from one another. bore and stroke. with those you can figure out your displacement of air and hence know what "size" the motor is
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guess I'm fairly well qualified then

 

no

 

Wow, what a wordy response. I remember you being a mod, and now you are not. I thought that would be a demotion. ?

 

I could be wrong; but I think he "retired".