Does this sound right

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B3422w5

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Talking with a guy on Facebook who has a 408 with Indy heads.
Cam is a roller 248/254@50
He claims on the dyno it makes peak power at 6800 rpm
To me that sounds really high with that small cam
 
I guess it depends on the rest of the build, but that does sound high.
 
He posted this

IMG_1503.jpeg
 
Possible.

428 X with a 686 lift Batten heads carb 950 peak power was at 7200
416 R with a 686 lift with indy heads carb 1050 peak power was 7900

The cam only plays a partial part of peak power.
 
Same here ..my W2 head 410 , 9 1/2 to 1 comp , 584/595 lift cam peaked at 6200 also
 
Imo, the number at 6800 is a glitch.
It’s rare that there is an upward spike in the tq curve after the numbers are well into the downward part of the curve.
The true peak looks like 6600 to me, which is still quite good.

If it had that little upward spike in the tq curve @6800 on every pull, then I’d say it’s a real thing, but if it shows up on a run or two, it’s a glitch.
I See it all the time.

Fwiw, I don’t know where it was tested, or what time of year, but the vapor pressure is super high……. Which is a big player in the correction factor.
 
PRH said:
Imo, the number at 6800 is a glitch.
It’s rare that there is an upward spike in the tq curve after the numbers are well into the downward part of the curve.
The true peak looks like 6600 to me, which is still quite good.

If it had that little upward spike in the tq curve @6800 on every pull, then I’d say it’s a real thing, but if it shows up on a run or two, it’s a glitch.
I See it all the time.

Fwiw, I don’t know where it was tested, or what time of year, but the vapor pressure is super high……. Which is a big player in the correction factor.
Click to expand...

Looks like he is from quebec
 
Can you see the name of the shop that tested it?

It would be on the first page.
 
no worries.
I had a few engines tested by a shop in Quebec in the 90’s.
Just curious if it was the same one.

That being said, .88 vapor pressure would be super high in that part of the world.
I’ve never seen it all that close to .88 here.

Was that tested recently?
Nicks Garage is up there too.
But that sheet is from a dyno that uses the old DOS software, and Nicks has had the WinDyn software for a few years now.
 
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I was just over at the Dyno yesterday with a 408 .
13.4 compression, ported trickflows with bigger valves, ported super victor intake, solid roller 263-270 cam and it was making peak power around 6800.
I guess those Indy heads could be big but I agree with prh, that is a glitch.
 
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What I found was 2' tubes with 3 1/2 collectors gave a total of around 1030 exhaust cfm flow and a 1050 cfm carb moved everything up. It pulled like a freight train on the top. If you want to run a big carb you need the exhaust and heads to go with it.
 
Here’s an example of almost the exact same scenario.
The tq curve is heading downward, then at 6600 there’s a little upward blip, then it continues down after that.
It did not do that on most runs.
If you look at the tq at 6500(388) and 6700(381), and averaged those two(384.5), the real hp number at 6600 would be more like 483.

It’s important to understand what you’re looking at on the sheet.
The dyno isn’t “measuring” horsepower.
It’s measuring torque, and calculating horsepower.
Little blips in the torque curve that won’t repeat from run to run……. Are just that. Blips.

IMG_3741.png
 
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PRH said:
Here’s an example of almost the exact same scenario.
The tq curve is heading downward, then at 6600 there’s a little upward blip, then it continues down after that.
It did not do that on most runs.
If you look at the tq at 6500(388) and 6700(381), and averaged those two(384.5), the real hp number at 6600 would be more like 483.

It’s important to understand what you’re looking at on the sheet.
The dyno isn’t “measuring” horsepower.
It’s measuring torque, and calculating horsepower.
Little blips in the torque curve that won’t repeat from run to run……. Are just that. Blips.

View attachment 1716336665
Click to expand...
I have one of my Dyno sheets that did the same thing.
 
MOPARMAGA said:
I was just over at the Dyno yesterday with a 408 .
13.4 compression, ported trickflows with bigger valves, ported super victor intake, solid roller 263-270 cam and it was making peak power around 6800.
I guess those Indy heads could be big but I agree with prh, that is a glitch.
Click to expand...
Sounds like that should get a thread started on it.:)
 
It’s not unusual to have the curve fluctuate a bit up/down near where the big numbers are happening in the meat of the curve, as various parts of the combo are coming in and out of tune.
But after the curve is solidly trending downward, and there’s one line that looks out of place(good or bad)……..it’s usually not a real number.
 
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