Firebird Nation banner
1 - 5 of 5 Posts

·
Registered
Joined
·
2 Posts
Discussion Starter · #1 ·
I have a 79 trans am I’m in the middle or restoring. The power train is actually good right now. I’ve passed emissions. Usually can get it up to 80mph without a issue, and have 3.43 gears installed with a recently rebuilt TH350 transmission. I went months back and bought a Pontiac 455 block. Thinking why not build the ultimate Pontiac street engine. I was going to get 9.3 - 9.5 compression and try for 400hp and 450-500 torque.
I bought the block and then found a factory crank and TRW forged pistons .30 over. Problem is after further research it seems the 400 is actually not far off the 455 and I can build power from probably just prepping my extra heads.Even the machine shop guys when I dropped the block and pistons off seemed confused that I would spend the money to build up a 455 when I have a fine 400.
My question is should I just sell the block and use the money to keep the 400 up to snuff or continue building the 455.
I’m looking to make a performance street engine. But I I keep the 400 I’m good with 300 plus HP and high 300 leve of torque. The current build usually sits at 180 degrees as well so it’s reliability is making me question the whole project. You guys have any advice.
 

·
Registered
Joined
·
1,182 Posts
Depends on the current condition and specs of existing 400, 400hp and similar in torque is not an awful lot. You can even do that with the weaker 400 block. The 455 would not be required unless you go beyond those figures or existing 400 needs similar work. If 400 is original to car it would be a bonus to keep.
 

·
Registered
Joined
·
625 Posts
You need to figure out what heads you will want to run to get you too 9.5 if iron and then if that new engine will have to meed smog?455s make 450-475 like falling off a log!400s not so much and be street comfortable to drive.Tom
 
1 - 5 of 5 Posts
Top