That’s the thing Mike. 1; The springs may not be all that. But there’s more to it than that of course.
2; He reported it feels like it noses over before hand. So he can’t tell exactly could be beyond that rpm range. If all else was good if the spring is the issue all by itself.
I don’t know what your ported heads flow. That could be one of several factors of performance leveling out, AKA, out of breath/head limited.
Going smaller on the carb is also a breathing issue. IMO, go back to the 750. You have enough engine for it.
Then there is cam vs cam. Knowing exactly what was there in order to compare would be good. There is more to the eye than the simple listed specs of the cam going on with cams.
In all honesty, the way you describe the engine/car performance, it all sounds about right. These things (engines as per your equipment) all seem to nose over around that point given your parts and listed specs.
When people build engines like yours and report what seems like way higher peaks in power, (RPM based only, not actual hp/tq numbers, another story in itself) there breathing track is normally consistent with better intakes, well ported heads etc... and sometimes secrect trickery that never gets listed.
Sometimes they never say/list all the little tweaks that make the difference! Degreeing the cam in at a different spec, head coatings, piston top coatings, polishing those parts, trick crank finishes, modded intakes, the list gets long!
I remember a local dyno test being done that I walked in on and it was a test of cylinder heads for the local roundy track. The trick aluminum head made less power than the pro prepped valve job only head and a Slaughter occurred in front of my eyes. It was over 50 horse difference. Another fine example is a simple addition to your valve train geometry. Mike at B3 has kits that fix this issue. (Which isn’t a huge thing but, as you read on... maybe it is and worth your time, your call.) In my opinion, it’s a good to do. A member here local to me, got a kit installed it ran his car at track and picked up a 10th+ at the low 11 second ET mark.
That’s easier than ripping weight out of your car.
(A shout out to Kevin! Ya man!)
