Hi I have a 67 catalina 400 motor in my 67 firebird are they all big blocks? how do you tell? Tired of being asked and not noing the answer. thanks for any help. Joe

All Pontiac V-8's back then were the same size. There was no small block. Catalinas, however, tended to have small valve heads and lower compression ratios than Firebirds, GTO's and Grand Prix's.

Yup,there all big block motors.

All 326-455 motors were the same dimensional size with only minor weight differentials.

Not to be confused with Chevy small/Big..

Or Ford :p

Ford

yuck

All true, yet the main difference was the 326, 350, 389 400 and 421 all have small Crank Journals, while the 428, and the 455's have the large Crank Journals.

Pontiacs have the large C.I. displacements, but truly no large or small blocks. Most will just refer to them as a Big Block Terms used for (Chevy, Mopar and Ford).

So just tell them they were all the same size block, just different internas to make more C.I. and much more HP! Not that they will really understand, but you tried!

Brett - 67 Drop Top 455!

(psssst ... Brett ... 421 also had large journals.) :p

Hmmm... I thought I always remembered talk of the 428 ans 455 cranks being interchangeable, but maybe since the 421 isn't as common it get's left out of the conversations...

I sit corrected! Lol...

Thanks, never claimed to know much anyway!

Brett - 67 Drop Top 455!

Actually, the '66 421 and 67-69 428 cranks are the same size (journals and stroke), but the 421 cranks are made from cast Arma Steel as opposed to cast Pearlitic Malleable Iron. The '65 and earlier 421 cranks are slightly different - although I don't know the details - but thay are also cast steel. The 455 and 428 cranks are physically interchangeable, with the exception of the 455's longer stroke. (Piston pin location is different between 455 and 428 pistons.)

pearlitic malleable iron??? man u guys are sick!!
LOL

At least Q is sicker than I am! Lol...

Brett - Sick But happy!