Does this estimate of horsepower sound about right for a Hemi?

[jayfire]

I did not build this engine, but the information listed below is what was told to me by the previous owner who had it built in the late 80's.
1968-426 original block bored .030 over
Arias 7-1 forged blower pistons
Crane hydraulic cam, unknown specs, but said it was mild
Stage V aluminum heads with all stock rebuilt rocker assemblies
TTI 2" primary headers to 3" H pipe dual exhaust
6-71 Weiand blower
Holley Sniper Stealth 4500 with timing control

The car runs good and pulls hard (68 GTX, 4 speed, Dana 60 3.23 gears) I have done a remote tune with a well respected tuner out of Texas. After reviewing my data logs, he said that I was at 330lbs per hour of fuel, which at that AFR was about 532-550 horsepower. Now that was at 5200 rpms with 62% throttle and 3-4psi of boost (I have the pulleys to be 12% overdriven) He said with more throttle, equals more boost, I should be around 600 horsepower max. Does this sound about right? The previous owner said he had this blower (bought in 1975 from Honest Charlies Speed Shop) on a low compression 440 with iron heads and exhaust manifolds and said it dynoed at 720 horsepower to the crank. He said it should be closer to 900 on the hemi. I'm starting to think I was fed some bovine fecal matter!! Does 600 HP sound more realistic? Thanks

 

[RemCharger]

A 6 71 is a little blower for a hemi. You have to wind them up to get more boost, which creates more super heated intake charge.. which is bad bad.
It's more for the look .
Knock the blower off, and a 426 should still be 6-700 capable properly built.

Judging power output at 62% throttle is kinda weird .
No way to get it to a wheel dyno?

 

[PRHeads]

Why guess?
Take it to a decent chassis dyno and make a few pulls..... then you’ll know.

600hp would be pretty easy to make with enough boost.
900hp from that combo is a giant stretch.

We had a 454 BBC here over the winter.
Old, very well used 6-71(with some pretty ugly looking rotors), 2 x 650 QFT carbs, mild SFT cam, ootb Brodix “Race Rite” rectangle port heads.
Made 668tq/709hp with about 7psi boost on pump 93.

 

[33 IMP]

You said you have pulleys for 12% overdrive. What pulleys are on it now?
With 7 to 1, and a mild hydraulic, I would much sooner believe 600 than 900.
As said above, 6/71 is a bit small, and when increasing blower speed, boost goes up as does heat, but power per pound of boost goes down.

 

[PRHeads]

Any boost gauge?
What are you getting at WOT?

 

[INTMD8]

Yes why not WOT? Could use another couple points of compression, IMO.

 

[jayfire]

No wheel dyno close. May have to take it to Phoenix or Vegas for that. I have a 33 tooth on the blower and 37 tooth on the crank. It was reversed when I bought it, but probably wasn’t producing any boost with it underdriven. It does get hot quick. I can give it more throttle, but the data log said that’s where it was at when I let off at 5200 rpm’s. I need to find some place close to open her up a bit more. This is on 98 octane.

 

[HEMI-ITIS]

Traction is another issue!

 

[451Mopar]

I did not build this engine, but the information listed below is what was told to me by the previous owner who had it built in the late 80's.
1968-426 original block bored .030 over
Arias 7-1 forged blower pistons
Crane hydraulic cam, unknown specs, but said it was mild
Stage V aluminum heads with all stock rebuilt rocker assemblies
TTI 2" primary headers to 3" H pipe dual exhaust
6-71 Weiand blower
Holley Sniper Stealth 4500 with timing control

The car runs good and pulls hard (68 GTX, 4 speed, Dana 60 3.23 gears) I have done a remote tune with a well respected tuner out of Texas. After reviewing my data logs, he said that I was at 330lbs per hour of fuel, which at that AFR was about 532-550 horsepower. Now that was at 5200 rpms with 62% throttle and 3-4psi of boost (I have the pulleys to be 12% overdriven) He said with more throttle, equals more boost, I should be around 600 horsepower max. Does this sound about right? The previous owner said he had this blower (bought in 1975 from Honest Charlies Speed Shop) on a low compression 440 with iron heads and exhaust manifolds and said it dynoed at 720 horsepower to the crank. He said it should be closer to 900 on the hemi. I'm starting to think I was fed some bovine fecal matter!! Does 600 HP sound more realistic? ThanksView attachment 1313766

I think with a BSFC of 0.50, the 330 lbs/hr is around 660 HP, and with a BSFC of 0.45, 733 HP
How to Estimate Your Engine's Required Fuel Flow.

 

[jayfire]

I think with a BSFC of 0.50, the 330 lbs/hr is around 660 HP, and with a BSFC of 0.45, 733 HP
How to Estimate Your Engine's Required Fuel Flow.

So, working the numbers backwards, it could probably be closer to 650-700 hp with the 330 lbs/hr as it was logged? I can give it another try with more throttle, more boost and see where the fuel in lbs/hr comes back at.

 

[jayfire]

Traction is another issue!

It’s only money

 

[INTMD8]

Still not understanding why-

-You would do a remote tune at only part throttle

-Care what hp it makes at part throttle

Trying to extrapolate 5,200 rpm, 62% throttle and 3-4psi boost to- what power does it make at WOT/max rpm is impossible.

 

[PRHeads]

The bsfc numbers shouldn’t align with what you’d typically see from an N/A application.
Some of fuel being consumed is used to turn the blower....... a parasitic loss.

 

[jayfire]

Still not understanding why-

-You would do a remote tune at only part throttle

-Care what hp it makes at part throttle

Trying to extrapolate 5,200 rpm, 62% throttle and 3-4psi boost to- what power does it make at WOT/max rpm is impossible.

The tuner asked to run it up to 5000 rpm’s. This is what the data log showed at that rpm. The TPS was at 62% with 4psi of boost. This is what he calculated the HP to be with this data. Once I get an alignment and can find a stretch of road that I can run, I will open it up more and send that data log to him and see what he thinks.

 

[33 IMP]

The tuner asked to run it up to 5000 rpm’s. This is what the data log showed at that rpm. The TPS was at 62% with 4psi of boost. This is what he calculated the HP to be with this data. Once I get an alignment and can find a stretch of road that I can run, I will open it up more and send that data log to him and see what he thinks.

You're in Bullhead. There is ample evidence that El Rodeo drive in Mohave Valley is used for the occasional street contest. Up near the dump, oops recycling center. Long straight downhill road, can see somebody coming up quite a ways away.
Been there, NOT done that, just sayin'.

 

[jayfire]

You're in Bullhead. There is ample evidence that El Rodeo drive in Mohave Valley is used for the occasional street contest. Up near the dump, oops recycling center. Long straight downhill road, can see somebody coming up quite a ways away.
Been there, NOT done that, just sayin'. There’s a shop out there that I may take it to to do the alignment.

You're in Bullhead. There is ample evidence that El Rodeo drive in Mohave Valley is used for the occasional street contest. Up near the dump, oops recycling center. Long straight downhill road, can see somebody coming up quite a ways away.
Been there, NOT done that, just sayin'.

There’s a shop out there that I may take it to for the alignment. Sounds like I can test it out on El Rodeo after it’s finished. Thanks

 

[451Mopar]

The bsfc numbers shouldn’t align with what you’d typically see from an N/A application.
Some of fuel being consumed is used to turn the blower....... a parasitic loss.

true, the numbers would be with no parasitic loss from the blower. Just trying to work with the data posted