[myam]

What 400 engine blocks were used in the 75 Firebirds? Did they use the same weak blocks as were used in the full size A-Bodies?

[ponyakr]

I've read that the 500557 blocks were used in later '75 models. The earlier '75 models still had either a 481988 or 488988 block, depending on what info you believe. Don't know the exact date when the 1st 557 block was used. The Wallace site says that the 488988 blocks were probably mis-cast with this number, in '74. I assume they are the same blocks as the 481988.

http://www.wallaceracing.com/enginesearch4.htm

Here's what Rocky said about the 488988 blocks.

"This somewhat uncommon block, #488988, was used in late-’74 400 applications and contains all the desirable characteristics for performance use."


Most of the time when I post a link to something, somebody will come on saying that info is wrong. So, I'll just say this is one of the sites where I saw 2 different number blocks used in '75. I have no way of knowing if the info is correct or not.

http://www.teufert.net/pontiac/bloccast.htm

[rexs73gto]

I don't know where i read it but I have always thought that the 557 blocks didn't show up until the very late 76 cars & early 77 blocks, & then Pontiac went back to the thick web blocks because of all the warr. issues in the last part of 77 & all the 400's after Jan. 78 were the thick web blocks . Thats why when you got a mid year car (400) you were assured the block was good for building it. I don't remember if it was a service bull. or if it was in a book but those facts do stick in my mind. I worked in dealers from 69-71, then a short stint in the Navy right after I got out of school & back into dealers in Oct. 77 until Dec. 2003. I read a lot of service bull's in that time so it could have been in one of them. I'm just not sure.

[myam]

on my 75 G.A. with the 400. I had the 557 block. So I pulled it for the crate engine I put in to get what I wanted for a healthy build.