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So I have a

400 sbc bored 40 W/ splayed main caps
scat crank
h-beam 6" rods
SRP flat top piston
rev kit
comp roller lifters vertical looking bar
comp 1.5 roller rockers
AFR 210 comp heads
super victor manifold
Quick fuel p-950 carb
501C2LUN Solid roller cam

So I went to the chassis dyno the other day and made 405 HP 5400 and 438 TQ @ 4700.

The cam the heads and the intake are all suppose to make power between 3500 - 7500 so why is my max power 5200-5400 and it falls off prety good by 7000. So what im asking I guess ….. what is it that moves the peak HP up the rpm scale?

At first glance looking at the components and how you describe the dyno chart I would guess valve float. Like you said the components are pretty well matched and just from looking at your set-up I would have estimated your peek HP at around 5800, and peek torque around 5200. And from the way you describe the sudden drop in performance that's probably where things are getting unstable. Especially with your torque /hp ratio lopsided like that. I would have expected to see those #'s reversed with your components. You already have an rpm kit to help stabilize the top of the valve train, so the only other option to help control the top end would be to go with lighter springs (weight not pressure), retainers and locks. That's assuming this is a set-up that sees the strip frequently. If it's only a street driven car that you never plan to take to the track I wouldn't invest the money other than maybe the rpm kit, and just accept your rpm limitation as you will very rarely exceed it on the street anyway.

Keep in mind you still have roughly 500hp and 550 ft lb of torque which is a very respectable small block.

1. Is you carb tuned with a wide band meter? If so what is your AFR at WOT?
2. What is your total advance?
3. What transmission are you using?
4. What exhaust system / headers?
5. Did you degree the cam?
6. What ignition?
7. Is that corrected HP and if so to what standard?

It's not bad numbers but not great considering the set up.

For comparison my 408 at the flywheel with 5.65 rods (procomp I beams, scat forged crank) has 450hp at 5100RPM and 500ft/lbs at 4100RPM at the flywheel with the stock water pump pulley set and alternator on it during the session. Numbers are corrected STP. I believe with my TH350 it should lose 15% based on what I have read - so that would be 382hp and 425ft/lbs on a chassis dyno.

-16cc SRP pistons (figure 10:1 static and 8.5:1 dynamic Compression)
XR276HR Comp Cams Hyd roller, degreed
650 double pumper tuned with wide band O2 sensors
Edelbrock RPM Air Gap Intake
Dart Iron Eagle 215 heads not ported
MSD Ready to run set for 38 total advance all in at 3000 RPMs
Dyno system headers 1 3/4 inch tubes through very large dyno mufflers

Cam timing could move the RPM up the scale - I personally think you have too much carburator on it but don't think that will be a big deal on the dyno - it will on the street though.

The hp is RWHP from my 68 camaro. It has a M21 Four speed, hooker side pipe headers w/ high flow insert, 6al disy, I did degree the cam it @ 7* advance, The AFR is between 12 and 13 threw the pulls. I also have a 1 inch spacer and 1/2 NOS plate. (The bottle is not in the car but its set for it). I Ran three Pulls

1) 403 RWHP at 5300 and 424 RWTQ @ 35* full timing by 2800
2) 399 RWHP at 5300 and 428 RWTQ @ 31* full timing by 2800
3) 405 RWHP at 5300 and 434 RWTQ @ 36* full timing by 2800

I would have tryed more * but it was closing time.

It has great pull threw the car it gos from 200 at 3000 to 400 at 5000 gaining 50 hp ever 500 rmp then plains off between 5000-5500. Im going to go again I started to think about it and i still have to set the valves lash hot. I set them cold before the first start. There at .016 a .06 smaller then the spec .022.that could be enough to throw it off at high rpm. It is so fun to drive dont get me wrong ive had 6 motors in this car in the last 16 years and this one is the best! It puts you back in the seat its a great street car idle is great It will go stop light to stop light all day long. I just thought there was a little low on the high side of peek HP. I know it's every bit 500+ at the fly wheel i was just thinking it should of been around 560 or so. I just thought i would pick some heads before i go back for round 2!