Anyone know if the post '77 350 & 400 blocks will fit our cars? I've read that they only used 3 mount bosses instead of 5. After I know whether or not it does, I'll make sure it's not a 557 block too. I came across a 400 out of a '78 TA pretty cheap and I'm thinking about grabbing it
Pontiac post '77 block question
- Thread starter G-Body_Vet
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It will fit but will be a 557. I wouldn't be concerned about the 557 for anything other than if you were building a race motor out of it.
I have the 301 mounts and brackets already for my 455 that I'm putting together. I'm still fairly new to Pontiacs and thought I recall reading something about certain blocks not fitting without fabbed mounts??????? I really want to have the car drivable this summer but realistically I'm a long ways away from finishing the build. I'd like to throw a 350 or 400 in it for the time being.
As for the 557 block goes, maybe I'm taking the PY forum stuff too serious. I was reading a thread over there and a lot of the guys seem to avoid them like the plague if they can help it. From what I gather they're prone to cracking and dropping the main cap dowels in the pan, whether stock or built.
I'm all ears if you guys have other opinions.
As for the 557 block goes, maybe I'm taking the PY forum stuff too serious. I was reading a thread over there and a lot of the guys seem to avoid them like the plague if they can help it. From what I gather they're prone to cracking and dropping the main cap dowels in the pan, whether stock or built.
I'm all ears if you guys have other opinions.
I have built several of these late block with that casting numer, all of them were around 350-450 horsepower and have never had a failure. There was a small write up in High Performance Pontiac about this subject and it says that these blocks are at a disadvantage in an all out race build but are ok at moderate performance levels. The stock 301 frame mounts and block brackets will work just fine, ive used them in a few g bodies with pontiac engines without issue.
What is a 557 block? The 5 mounting holes were to cover both the pre-70' models that only had 2 mount holes, and the 70'+ models that had 3 holes, so service replacement blocks would fit all cars. By 76' or so they had few calls for 70'+ blocks going into pre-70' cars, so the other 2 holes were dropped. It probably saved $.06 on each block. This was told to me by an old-timey Pontiac parts guy. The only time you need adapter brackets is when a 2 bolt hole block is used with 3 hole mounts, and vise-versa. Even then they are cheap and even can be fabbed at home.
Bonnewagon said:
Thanks for clearing that up about the mount bosses.
I borrowed this from http://www.angelfire.com/fl4/pontiacdude428/block.html
"400 Blocks produced after 1975 with the last 3 numbers #557 have an undercut support area from the main to the pan rail & I don't recommend for 400hp plus builds."
Here's a few threads about that block too.
http://forums.performanceyears.com/foru ... p?t=663490
http://forums.performanceyears.com/foru ... hlight=557
http://forums.performanceyears.com/foru ... hlight=557
Man, that's news to me. Thank's for that info and links,I guess it was never as issue since most guys built the "good" blocks from the 60's early 70's. I probably have one of them in my 77' TA, original motor. So far so good but it's a very mild set up. This guy's motor is toast!
Definitely fragged for sure! If I came across one for a good price I'd run one myself since it wouldn't be getting built. I'm still hoping to find a dirt cheap 350 to play with for the hell of it.
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