I only turn it about 6500 at the traps. When we built the motor originally that was one of my stipulations. It made peak at 6600.
We tried the 660's, they were fatter then the 600's but power fell off. I would have like to see what the 750's would do, but wasn't in the cards Saturday. The whole dyno deal all came up real quick and I wasn't able to get all my ducks in a row like I thought. Waiting for the next slot might have been awhile and I just decided do with what I have. There again, buying $1700 worth of carbs is not really in the budget right now(what friend paid for his two).
Distributor is locked out. We played with timing and it didn't really change much power wise.
First, always easy to armchair, and we aren't writing your checks LOL. Always need to remember that these are the days...when could you bolt together mostly off the shelf parts for 650 HP in an FE. It's a cool engine and I am not throwing stones in any way
However, I would like to clarify a couple after your response
1 - My comments are only to throw out ideas because you mentioned you would have liked to see 700 HP, nothing else
2 - I have never seen 660s not make HP over 1850s, even on smaller engines So my thought goes to two things, either bad 660s, or the ignition. Not a curve issue, but maybe a bit of a ignition problem that wouldn't let more cyl fill do it's thing. Just a thought, too bad the 750s couldn't make it on their, I think it would have liked it. Something to look at would be a close look at the curve/numbers to see if it was getting funky up top. Could even be a valve bounce or float that is acting like a governor. Just a thought without seeing the sheets
3 - The cam discussion wouldn't have revved it higher (unless you wanted that). TFS behave differently than other heads. The intake port is real good for it's size. However, a second part of it being good is it's small and reacts quickly, it doesn't need or want a ton of overlap to pull it along using the exhaust pulse. So you can spread the centers and they are happier (wider LSA) . The exhaust on an TFS though is good, but not as good as the intake, so they tend to like more duration to empty the cylinder. So lets say you used the exhaust same intake lobe, but more exhaust lobe and spread them, you'd likely make more power everywhere, not really an RPM increase.
Would those changes reach 700 hp? I think so but, it really depends on the intake too, it may need some rubbing. However, I am not a tunnel ram guy, but I do like playing with runner length math and what you are seeing makes sense...more torque for a given flow. That being said, I think there is more in that bad boy
Again, no negatives, as I said, when you can run gallons of fuel through the dyno, not break and then go racing with over 650 HP, that's a good one. Just bench racing based on your 700 HP comment