6/71 roots

[rocketracer380]

How much power can be made on a race fuel 440 " stroker Oldsmobile?

[Krooser]

We figured my mild blown 354 Hemi was about 600 with a mild hydraulic cam, single 750 Carter and 8lbs of boost...

[F-BIRD'88]

How much power can be made on a race fuel 440 " stroker Oldsmobile?

A blower acts like a amplifier. How much power does this engine make without the blower on it?
In simplistic terms it will amplify that.
And it will depend on the blower drive speed too.
if you want to make the most power with that blower use Methanol fuel.
It has a BIG intercooling effect.

[mag2555]

At about the 800 hp level a 671 is adding too much heat if even overdriven only 20 % so at this point a 871 is the way to fly.
And don't forget , the size of your Carbs control the boost level in a big way also!

[mag2555]

Or look at it like this.
The 671 was designed to feed a 6 cylinder motor of 426 cid at 3000 rpm or so, you on the other hand have a 440 cid motor that will likely turn 6000 rpm or better!

[F-BIRD'88]

The 6 cylinder engine is a 2 stroke.
Twice the power strokes

[lefty o]

The 6 cylinder engine is a 2 stroke.
Twice the power strokes

2x the rpm=much more heat.

[Keith Morganstein]

The 6 cylinder engine is a 2 stroke.
Twice the power strokes

2x the rpm=much more heat.

Worth noting however, The function of the blower on Detroit two stroke is that of a scavenge pump, not a supercharger.

[mag2555]

That's true and I forgot that when EMD needed to get above 2250 hp on there 567 16 cylinder motor they had to add a Turbo that was both gear driven at low rpm and then freewheeled at higher roms to just be driven by the Exh.

They had a few teatihing problems at first getting that to be 100% to say the least.

As I recall EMD used 1 Blower for each bank of cylinders for the 567, 645 and 710 motors , with there new 16 cylinder 265 motor they had to go to a 4 cycle motor to match GEs 5000 hp.

[cuslog]

I was with a friend last week, he was dyno testing a 468 BBC with a B&M Megablower (6-71 size), 2 x 850 Demons, 7.5 C/R. smallish cam
Made ~ 800 hp @6800 at 15% overdrive, ~ 830 at 20% overdrive, 835 at 32% overdrive -- dyno operator figured it was running out of fuel at the 32% overdrive (small needle & seats = seemed to take a long time to fill the bowls) also said the C/R was a bit low for that size of blower (either more C/R or more boost from a bigger blower (cooler charge) would have made more easily.
Had a real wide torque band, starting at about 4000 was well over 700 tq. and held it.
These are a stripped blower, so probably a bit more efficient than a non-stripped 6-71.

[oldhead]

My SBC-400 made 470 hp(8.1 to 1),Added a 871 running it at 13% over made 725 hp(16#), at 19% over made 710 hp(Full of hot air)Made 36 pulls.................Installed a Vortech YSI With the lowest boost pulley they sell made 875hp at 15#, changed pulley went to 1004hp at 22#, Made more then 41 pulls(testing nitrous) . ....My friend went to make more then me,spent much more then $7000 added 12-71 and two 1250 domnators and got 948 hp. 671s are not the what to make power due to hot IAT gas, Alcohol is a different story Oldhead PS: Your Olds with 8# would pick up about 150 HP

[oldhead]

We figured my mild blown 354 Hemi was about 600 with a mild hydraulic cam, single 750 Carter and 8lbs of boost...

Is that a single 750 on a 671 ???

[oldhead]

At about the 800 hp level a 671 is adding too much heat if even overdriven only 20 % so at this point a 871 is the way to fly.
And don't forget , the size of your Carbs control the boost level in a big way also!

If I remenber right compairing the 671 to 871 are very close to the same size, the 871 is about 6% larger
which would be less then 1# of boost at 1 to 1 drive ratio Oldhead

[panic]

JM2¢?
X-71 = OBS
Until you run out of capacity or drive speed the modern centrifugals outperform positive displacement.

[Krooser]

We figured my mild blown 354 Hemi was about 600 with a mild hydraulic cam, single 750 Carter and 8lbs of boost...

Is that a single 750 on a 671 ???

Yep... built a very mild motor for a daily driver... 4 speed o/ d... 3.54 rear... sold the engine... the new guy seems happy with it.