Hemi Dyno Sheet Thoughts

[dadsbee]

Honest thoughts on these numbers lads. 426 Hemi, Stock crank, 0.040 over pistons and a 520 lift cam is all I know..

 

[pnora]

That's making some good power. What is he running for carbs? At first I was thinking that he was a little high on RPM'S to make that much power. But the more I think of it my old wedges were in the 6,400 to 6,600 range. My 528 stroker hemi made 652 Tq at 3,700 and 642 Hp at 6,100 .

 

[dadsbee]

I presume that dyno run in 2016 was done with the correct dual quads for the engine, as I'm getting those in the deal. I believe that the engine currently has Eddies on it.

 

[Jerry Hall]

My feelings are it's not, it's not 10.25 compression anymore. Also the power is not coming on enough in the 3000 rpm range. A completely stock Hemi is much better than what I'm seeing.

 

[qkcuda]

Street Hemis were rated at 490 lb/ft of torque at 4000 rpm and 425 horsepower at 5000 rpm. It was always said that Chrysler fudged the numbers by just recording horsepower at lower than peak rpm to keep it under the magic 1 horsepower per cubic inch for insurance purposes. That dyno chart doesn't surprise me in the least with a hotter than stock cam. Notice the torque peak is moved up by 1000 rpm, but horsepower is only 32 higher at 5000 rpm than stock. I drove my buddy's hemi RR once and I can tell you it just kept pulling at high rpm.

 

[PRHeads]

The correction factor varies by about 6% from the beginning to the end of the pull.
A change in air density enough to equate to a 6% difference in correction factor in what might be a 10 second dyno pull?
Not likely.

I have seen similar inconsistencies on other dyno sheets where a Depac data acquisition system was used.

I think if you saw a sheet that had the uncorrected tq/hp on it, the curve wouldn’t have as much of a spike near the top of the pull, where the CF has climbed to 10%.

 

[pnora]

There is some odd things going on. Both the Torque and Hp are very irregular.

 

[33 IMP]

There are a couple dyno runs of a similar 426, and a 440 sixpack, on an engine masters episode. The 440 completely destroyed the hemi, below about 5200, then the hemi showed up. I'll review the episode and post numbers.....

 

[33 IMP]

440 sixpack at 9.5 to one, hemi at around 9 to one (old mp crate hemi, but fresh.)
Both engines with the same hyd roller, 235/241 at .050, mid .5 lift.
Peaks, 440, 525 ft pds at 4200, 488hp at 5500
Peaks, hemi, 479 ft pds, at 5000, 513hp at 6200 (still over 500 at 6500)
The 440 at 4200 was 60ft pds, and 50hp, better than the hemi.
440 completely done at 5800, hemi just starting to really run......

As for the posted dyno run, why is the correction factor wandering all over the place?
Is that a Mopar performance crate too? If it is, probably a nine to one engine.

By the way, if I had a chance to get ANY hemi, I would do it, and find something appropriate to put it in..... my 49 business coupe? A 33 Imperial sedan? Hmmmmm.

 

[Fran Blacker]

Is that engine in that picture of the unicorn 66 and your buying it?

 

[dadsbee]

As for the posted dyno run, why is the correction factor wandering all over the place?
Is that a Mopar performance crate too? If it is, probably a nine to one engine.

As noted by PRHeads... a shitty operating system, which probably equats why the torque is in and out on it's way through the rpm range. At least the HP is a constant climb.

Not a crate engine...

 

[dadsbee]

Is that engine in that picture of the unicorn 66 and your buying it?

Well I ordered this plate last night for something.. time will tell...

 

[PRHeads]

The clue that something hinky is going on with the CF is clearly seen at 4700-4900 rpm, where is changes almost 5% in those three lines on the sheet.
4.95% at 4700........ 9.7% at 4900.

Bsfc is derived from the fuel flow and uncorrected power.
If you know the fuel flow and bsfc number..... you can determine the uncorrected hp.

The fuel flow at peak hp was 299.4, and the bsfc number was .67, so 299.4/.67= 446.8 uncorrected hp for that line of data.

Looking at it a bit further....... for 4700-4900 rpm the uncorrected hp curve doesn’t mirror the corrected numbers at all...... because of the screwed up CF.

Uncorrected:
4700- 384hp
4800- 389hp
4900- 404hp

I’m used to seeing minute CF changes that look more like this:

 

[dadsbee]

Fuel flow is up and down like a yo yo through the entire run. From that I'd suspect the entire run sheet is hookey...

Guess we'll just have to see what it does to the tires....

 

[33 IMP]

Fuel flow is up and down like a yo yo through the entire run. From that I'd suspect the entire run sheet is hookey...

Guess we'll just have to see what it does to the tires....

It'll need gear.... inaccurate quote, but frieburger said that when he took the 5.13s out and put in 3.91s (might have been 3.73s) it "knocked the guts out". His 70 hemi bee went from 10.60 to 11.70. I realize Dad ain't racing, but any hemi will need SOME gear.....

 

[Crackedback]

The correction factor varies by about 6% from the beginning to the end of the pull.
A change in air density enough to equate to a 6% difference in correction factor in what might be a 10 second dyno pull?
Not likely.

I have seen similar inconsistencies on other dyno sheets where a Depac data acquisition system was used.

I think if you saw a sheet that had the uncorrected tq/hp on it, the curve wouldn’t have as much of a spike near the top of the pull, where the CF has climbed to 10%.

With 60* air 30" Baro, I'd expect a REALLY humid environment to get a 10% factor or serious altitude. Says "Dry Air" Something is amiss.

 

[PRHeads]

I’d say that about 1/2 the dyno sheets I see posted on line....... have “strange” things on them.

Fuel flow fluctuations are pretty normal, but the broads swings in flow on that hemi sheet aren’t what I’d like to see.

 

[dadsbee]

It'll need gear.... inaccurate quote, but frieburger said that when he took the 5.13s out and put in 3.91s (might have been 3.73s) it "knocked the guts out". His 70 hemi bee went from 10.60 to 11.70. I realize Dad ain't racing, but any hemi will need SOME gear.....

It'll just have to work with the factory 3.54's in the back!

With 60* air 30" Baro, I'd expect a REALLY humid environment to get a 10% factor or serious altitude. Says "Dry Air" Something is amiss.

There's no such thing as "dry air" in Canada.

 

[Crackedback]

It'll just have to work with the factory 3.54's in the back!

There's no such thing as "dry air" in Canada.

Canada, that explains it, only 75%

 

[PRHeads]

With 60* air 30" Baro, I'd expect a REALLY humid environment to get a 10% factor or serious altitude. Says "Dry Air" Something is amiss.

The 60*, 30”(29.92 actually), “dry air” is what it’s corrected to.

10% isn’t that unusual of a CF.
A CF that changes 6% over one dyno pull is.
That’s pure GIGO right there.

I’ve actually seen some dyno sheets where the CF changed like 20- 25% throughout the run(higher CF at the top end).

Needless to say, the cars performance didn’t live up to the inflated CF HP number.

Of course, pointing out the big hp numbers on the sheet are bogus because of the GIGO CF isn’t very well received.