Looking at the power curve you will notice that the stage 4 cam compared to the stage 2 cams with larger displacement shows the engine needed a better cam profile to breath up top as the Power and TQ Curve started diving compared to my combo.... there is a couple of reasons....
1. My heads were ported and flow much better throughout the lifts with about 25 more CFM at .600 lift compared to the stock 44cc TFS heads... NOTE: stock TFS head have reversion around .570 to .600 lift for flow and ported they kept going to .600 lift.... with a .575 cam profile, the sweet spot was about . 565 to .570 lift with the stock heads... so porting alone will better help larger flow/lift cams to .580 lift...
2. To me, it looks like for every 15-20 cubic inch increase, the modular needs 1 more stage up on cams due to increased displacement.... keep in mind, with the size of the bore on a stock 281 shrouds the valves due to narrow/limited size.... So, with ported heads, the 323 should have closely mirrored my power curve.... so, a stage 4-5 cam is good but need to see how that engine would have responded with better flowing heads/peak power which would flow more across the top of the chart...
3. Assuming a stock 281 long block with stock TFS Heads and cams average around 330-335hp with good bolt ons/exhaust with a 10 to 1 CR with a slight bump in compression, comparing to my combo with ported heads, with better intake combo, electric water pump, and full bolt ons hit 355 or about 20 more HP on the stock 281 bore, this tells me there was about 20-30hp left on the 323 combo with ported heads, correct cam combo, and a few other tweaks with bolts ons to help free up HP.... Things like alumium DS, Flywheel, underdrives, electric water pump, 375 to 410 gears have the potential to free up HP with this combo.... It did on mine... Also, both combos on this chart have 11.34ish to 1 CR so direct correlation when it comes to compression ration...
4. Intakes - the 323 combo was running a stock Bullet intake, where mine was running the PI Intake, Spacer, and BBK85 mm combo.... as noted in some of my previous posts, the
BBK combo was worth nearly 10hp and 10 tq over the Accufab plenum and 75mm TB.... I believe the better head flow and higher CR was able to take advantage over the accufab set up..... Now Richard Holden did intake comparisons on youtube which compared the PI intake with the accufab combo compared to the Bullet and many others.. (check youtube to watch videos for 2v intake comparisons) ... The Accufab combo ran identical to the Bullet...... originally, the bullet outperformed the stock PI Intake and TB by 5hp so the Accufab on the PI matches the bullet in performance..... since I have charts showing the larger 78mm bbk combo did better overall on higher compression set up over both the accufab combo and bullet on my car this is a must for higher CR/top end flowwing cars.... Only thing left would be shorter runner intakes which will give you 20-40 more HP on top at high RMPs but lose low end torque by 20-40 hp depending on intake.... there may be a balance with larger displacement when running say the Vicor Jr EFI intake with the 78mm BBK combo.... only testing would tell with the 323 combo...
Please let me know if anyone has any feedback or questions... just looking to help others and learn more while I start my new build...