I mean absolutely no offense by this. So, if anybody takes it that way, your wrong !
BUT, I don't believe it !
Think about what you're saying. You're expecting us to believe that your power increased by 100hp, with nothing more than a change from a well prepared & tuned 750 Q-jet, to a box stock Holley spread bore 800.
There are lots of 750 Q-jets running low 9's & even high 8's in Super Stock legal drag cars. These cars are making well over 500hp. IF a 750 Q-jet was that restrictive, they would never run that quick.
I suspect a dyno results error. OR, something wasn't right about the Q-jet. If a spread bore Holley is that much better than a Q-jet, it is the best kept secret in the history of hot rodding. As long as they have been around, somebody would have discovered it, either on a dyno or a drag strip.
Did you report these dyno results to Cliff Ruggles ? I'd LOVE to hear his opinion !
I do know that some of the higher hp BBC engines came with a square bore Holley. I think the most popular one was a 3310-1, which was called a "780".
"...I am making 490hp 577 tq with no trick or fancy stuff. No porting, no trick anything..."
Just for kicks, list all the specs for your 490hp engine. A Pontiac engine with no porting or trick anything, don't make 490hp.
Here's a typical pump gas 455 build, that is said to make aprox 425hp. I suppose if it was to use your Holley carb, it would make well over 500hp, with no other changes ?
http://lenwilliamsautomachine.com/455_Long_Block.htmlNow with ported heads & a good HR roller cam, that engine could make closer to 500hp, even with a 750 Q-jet.
https://www.gtoforum.com/f178/opinion-carberater-400-motor-86857/index2.html#post624025https://www.gtoforum.com/f178/opinion-carberater-400-motor-86857/index3.html#post624121I have no quarrel with anyone who has a different opinion than mine.