[AIR RAM]

I know some will say go to an aftermarket block... if that's your response, please move along to another post. This is about data collection.

I'm trying to put some information together that may be helpful for those who are about to build up their Cast Iron Pontiac blocks. The idea is to identify the limitations with more of a mathematical approach than a generalization approach. Most of the information I have found has placed a HP number on the limitations however this is a very loose limitation as there is little consensus as I have heard as low as 600 and as high as 1300... I have to assume there where inconsistencies in those builds that led some to fail low and others to live high...

I have been unable to find any real information about block limits when it comes to what the specs of the failed blocks where enduring when it comes to rotational mass, inertia forces, stroke, Piston speeds @ Rpm. I personally believe these all play a part in the blocks ability to hold things together. Case in point, you can have two engines making the same 700HP yet both have completely different parts with completely different rotational mass. One built with heavy components will likely add more stress to the block than one built with lighter parts.

So instead of giving a generic HP number... Id like to see a list of parts used and their weights. From there we can figure out the Inertia forces and piston speeds... And if your block is still together, do mention that fact. If you have specs on blocks that have given up the farm, by all means those are the numbers we really need to see.

My hope is that this information would help give a better understanding of the actual limits of our cast iron blocks.

I'm working on a build, and so far the specs I have are on the heavy side... So I will have to chose my cam to work within the limitations of those weights and inertia forces...


1974 455 block
Stroke = 4.5
Bore = 4.19
Pistons = 501 grams
.040 dish
Wrist pins .990 x 2.50 (Titanium) = 102 grams
Locks = 4 grams
Rings = 36.70 grams
Rods 6.7" ARP2000
Rod big end = 560 grams
Rod small End = 254 grams
Splayed mains
Mega Brace x3
80lb oil pump
EDL 72cc RP Heads = 340cfm (2.19/2.77)
ARP everything
(Topped off with 15psi)

Inertia force @ 6500: 5,682.36lbs
Piston Speed @ 6500: 4,875.00 fpm

I will likely chose a cam that will be in and out by 6000RPMs if the above proves to be excessive for the block.

Inertia Force @ 6000:4842.77lbs
Piston Speed @ 6000: 4500 fpm


I want to thank everyone ahead of time for your help in collecting this data.