A Moparts member, Larry Curtis, AKA lowflyingDart, built this 572 cu in iron block motor for a local racer.
4.5 bore 4.5 stroke, 14.5 compression, .043 top and 2nd rings. Comp roller with 284/296/112 cam in at 112, with . 836 gross intake lift, .824 ex lift. Intake lobe is a 24140b Comp, forgot the exhaust.Fuel ended up being VP c14+, which produced a few more hp (7?) Than c14. Timing ended at 37 degrees for best power. Carb is a 1250 Dominater, with a one inch high cloverleaf spacer on top of the Indy 3X. If there is a revised 3x, this would be it, new in 2022. Heads are 385cnc 572-13, with a minor touchup at the valve boss area to remove a small lip left by the cnc cutter. The final power pulls with 2 1/4 dyno headers are 962 hp. We tried my 2 1/8 step to 2 1/4 with merge collecters, and gained a few hp, to 967 hp and the increase was from 6000 rpm to 7200. I was very happy to see my headers produce more power than the dyno headers. Mine have a 4 inch collecter with 3 inch merge ( choke) and primarys are 30 inch. Larry was hoping for 950 hp, and considering leaks kept vacuum to a best of 4 inch, it is assumed this motor will make 980 hp when vacuum is up to 10+ inch. All in all, a very good result, IMHO!
I am happy to see this power level, as i have a similar build. Mine will be 550 cu in, but will have narrower . 9mm (.036) rings, ported 3X, methanol, terminater 2500 cfm injection, and the heads are cnc385 572-13 with extra port work by Larry Smith, and a similar duration @.050 cam, but . 032 more intake lift and more duration at . 200 lobe lift. My intake valves have no back cut, so it will be interesting to see how that works

Max Gromski, owner/ operater of R&R dyno service, is great to work with. SUPER FLOW902 dyno. Thats Max in the second pic

Looks like it wants a bigger carb

NIce!!
Hangs on good right to the end

Me thinks it wasn't done
I've seen several BB Mopars slow down and flatten out below the actual peak and then make more power 300 RPM after flattening out.
I now make sure the motor HP is going downhill by 500 RPM after the actual peak HP on all the engines that I dyno test now

First, thanks for posting the dyno results and engine combo.
Second, nice to see your header build worked well. I am guessing the extra HP was mainly due to the shorter primary tubes. But other differences can contribute. And 5 hp more at basically all RPMs that you will use at the track is a nice improvement (no downside).

Good numbers According to wallace our 580 (4.530 x 4.50) 12.5:1 makes 920hp (on a good day) it's very similar (even the headers) but with a T/R and 2 x 1150. We use an Indy cm 3 cam with 1.6 arms which works out at .768" gross lift. I'm considering switching to 1.7 arms (.816" lift) ..... so maybe a 25-30hp increase
Does anybody think it would be worth it ? Apologies for the hijack. Some car info below in sig.
TIA.

Jim, the huge upside was my new headers outperformed the dyno 2 1 /4 headers by 7 hp, and those dyno headers outperformed my original headers on a previous build by about 10 hp. So a guestimate is, the new pipes might have a 15 hp to 25 hp edge over my old set.

Tig, a rocker change might not increase power that much. A lot depends on the cam profile and duration. Do you know the . 050 duration and . 200 lobe lift duration of the cm3 cam? It is possible the tunnelram may not perform as good as a 3x intake. I am not sure, but heard Indy made changes to the 3x recently.
I So much depends on the chassis and driveline, anything not just right and it drops the estimated power output. So i don't think most calculaters are spot on.

Good numbers. I always like a good dyno day.

Hey Greg, what was the correction factor that day?

The duration @ .050 is 284in / 300ex, .480" / .450" lobe lift. 108 / 116 CL. Don't know the duration @ .200". We picked up a little going from the 3X and a 1250 to the T/R with 2 x 1150 dominators. The 3X used to run 1 and 2 lean, porting improved it but did'nt eliminate it entirely. The T/R seems to have better fuel distribution. Agree on the chassis but in defense it seems to work well for the weight of the car, 1.37 on the back wheels and 1.32 when it's not, I'd be surprised if it made over 920 on a dyno.

7100 corrected made 967, uncorrected would be 904 using the the lb fuel & bsfc

What I get from Wallace@938fwhp/4023lbs

60 Foot E.T. : 1.32 Seconds
1/8 Mile E.T. : 5.97 Seconds
1/8 Mile Trap Speed : 113.79 MPH
1/4 Mile E.T. : 9.47 Seconds
1/4 Mile Trap Speed : 142 MPH

It's not too far off those figures. Best are 1.32, 6.00 & 9.51. MPH is marginally better at both increments, we've been over 114 at the 1/8th a couple of times and just over 142 in the 1/4. Wallace gave me 900 and 920 going off weight, best et and mph. I think the motor is pretty much around 900 but it's never been dyno'd.

Thank you

Not sure, air was good, operater said actual power 7 hp lower than corrected

Tig, that is great performance for 4000+ lbs! Off your performance only, sounds like Wallace is conservative when comparing to dyno hp. What trans and rpm shift points? I am assuming most race days you see DA under 500 to 800 feet?

Thanks , we're using a home built 727, it has good stuff in it, we've broke quite a bit of stuff in there over the years . Manually shifting at 6700 and letting it do what it does through the lights usually works out best.
We're going to change the converter for next season, we were definitely blowing through it after a gear change from 4:10 to 3.73 (done to stop the big wheelies). Stall has gone up to 6000 (from 5200) and slip is 16% at the line. Car has always been heavy, it's a European market '74 and weighed 3700lb with me and a 318 in it
We can see -ve D/A first thing in the morning spring and fall, it's normally around the 1000 - 1200ft though, on my ET predictor.