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I built my 400 for around $4k , maybe a little over. But I updated most everything. New forged rods, Pro rebuilt my Q jet, MSD ignition, etc. pulling 377hp and 460 torque on dyno. My build sheet in my bio.
 

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Discussion Starter · #24 ·
The 557 block was a 400 block, never a 455 or a 350 as was mentioned. No 350 or 455 blocks were cast with a number 500577
Jim is correct and I concur. Keep your build at or below 400 horse on the 557 block due to slightly weaker main saddles
Still will make a nice street motor and run on pump gas if you get your "recipie" together correctly.
Personally I would freshen it up, stock, and run a Q jet. use a comp cams extreme energy cam to help it along. It would run decent for cheap. You can take time and build a nastier engine then while still enjoying the car, then do a weekend swap once the killer power plant is hatched.
Which heads are on that thing?
That’s actually a relief, I was almost positive with my luck that it was going to be a weaker block and I wouldn’t be able to achieve my goals. I might just putz it around this summer and locate a Pontiac 400 from 60’s early 70’s to build while the car is still in action. I haven’t had a chance to run down my dads to see what the casting code is on the stock heads. The guy I bought the car from told me the motor is junk but works. It’s been going for 10 years but I only drive it occasionally. She looks nice but I’m ready for her to drive nice now
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Wheel Tire Car Land vehicle Vehicle
 

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Go grab a copy of the June 2021 issue of Hemmings Muscle Machines.
It has a full TECH article on a pump gas 400 build that made 546HP / 635 ft-ilbs. It's a full recipe P/Ns and all. With that info you can research the cost.
 
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That’s actually a relief, I was almost positive with my luck that it was going to be a weaker block and I wouldn’t be able to achieve my goals. I might just putz it around this summer and locate a Pontiac 400 from 60’s early 70’s to build while the car is still in action. I haven’t had a chance to run down my dads to see what the casting code is on the stock heads. The guy I bought the car from told me the motor is junk but works. It’s been going for 10 years but I only drive it occasionally. She looks nice but I’m ready for her to drive nice now View attachment 142310 View attachment 142310
So it's road worthy now? I wouldn't tear it apart at this time of year. Mine blew up last June and I may have it put back together by June this year. These projects have a tendency of taking a long time to do. Both shops I used (one for the block and one for heads) had very long lead times. If you are planning on rebuilding what you have, you may be able to put your name in line at whatever shop you plan on using and pluck the engine at the end of summer or when your turn comes up (small deposit to hold the position?). It only takes a couple hours to pull the engine and a few more to tear it down to the bare block if you're going to be doing the disassembly yourself. You can have it out and ready for the machine shop in one day if you hustle on it. In the mean time you can be out enjoying the car as it is.

Nice looking GTO. Love the color! One question. Looks like you're running American Racing (or similar) wheels. Are those 15 or 16 inch? I've been thinking of going with something similar on mine but leaning towards 16". Trying to get a mental picture.
 

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Discussion Starter · #28 ·
So it's road worthy now? I wouldn't tear it apart at this time of year. Mine blew up last June and I may have it put back together by June this year. These projects have a tendency of taking a long time to do. Both shops I used (one for the block and one for heads) had very long lead times. If you are planning on rebuilding what you have, you may be able to put your name in line at whatever shop you plan on using and pluck the engine at the end of summer or when your turn comes up (small deposit to hold the position?). It only takes a couple hours to pull the engine and a few more to tear it down to the bare block if you're going to be doing the disassembly yourself. You can have it out and ready for the machine shop in one day if you hustle on it. In the mean time you can be out enjoying the car as it is.

Nice looking GTO. Love the color! One question. Looks like you're running American Racing (or similar) wheels. Are those 15 or 16 inch? I've been thinking of going with something similar on mine but leaning towards 16". Trying to get a mental picture.
Yea, the car runs almost as smooth as my daily driver but it’s just severely underpowered. I did a lot of suspension work last year and upgraded to disc brakes up front. I have 15” wheels on it, I bought the wheels that should be on it but I just never got around to installing them (they need a little TLC) thanks for looking! Everyone has been very helpful!
 

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Discussion Starter · #29 ·
I finally made to the old heads from my 400. It appears to have “16” as the casting code. I didn’t a Google search and it seems it’s from a 400 68 Gto. Just wanted to post on here if anyone wanted to weigh in. thanks
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If that is a 500557 cast block, end your 450HP goal right now. That is a late 1970's block and is a weak block - weak main caps/lower block mains. My be good up to 400HP, but even then, I would not invest a dime into it. HP ratings were low at that time, so Pontiac saved money by paring weight from the engine and this made it weak for any kind of high performance use. Pontiac recast the earlier blocks for the Trans-Am because these blocks did not hold up so well with the type of use these cars got.
I found Kauffman racing has multiple choices on heads that are also fair pricing
 
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