Re: What Size Blower for a Gen I street 392 Hemi?
[Re: B1arno]
#2145867
09/02/16 01:36 AM
09/02/16 01:36 AM
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Joined: Aug 2003
Posts: 43,228 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,228
Bend,OR USA
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I can't tell you the exact size differences internally between the standard case and the big bore case because I don't know that I was ask to inspect and tear down a street driven blown BB(454 C.i.) Chevy years ago, it had a small bore BDS blower on it with two Holley 650 D.p. carsb on it. I had called BDS to find out what is was and I was told off the information they ask about it that it was a small bore 6:71 That motor made 620 HP at 5 lbs boost on CA pump swill back in the late 1990s, I hopped it up some, cam change, pulley change and carb. size change and got 780 HP out of it with 7 lbs of boost, NOT GOOD I built and dyno tuned a blown 484 C.I. gen 2 Hemi with dual 1050 CFM Dominator carbs. with a Littlefield 10:71 blower, that motor made 920 HP on CA pump swill at 7300 RPM with 7 lbs of boost It made 1027 HP at 6500 RPM with 12 lbs boost on race gas going into detonation If you could mount and safely use (clear the distributor or run a crank trigger ignition)a 8:71 on your motor that would be better than the smaller 6:71 ) You can turn the bigger blower slower to make the same amount of boost with cooler manifold inlet temps. which will make more power due to the cooler denser air with more fuel mixed in it
Last edited by Cab_Burge; 09/02/16 01:37 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: What Size Blower for a Gen I street 392 Hemi?
[Re: B1arno]
#2146070
09/02/16 12:33 PM
09/02/16 12:33 PM
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Joined: Jan 2003
Posts: 28,068 Irving, TX
feets
Senior Management
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Senior Management
Joined: Jan 2003
Posts: 28,068
Irving, TX
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Don't get suckered by boost numbers.
Boost is a resistance to flow. Good flowing heads and a proper cam will show less boost than poor performing components with the same blower and drive on the same bottom end.
I made more power at 8 psi with the Eddy heads and good intake than I did with the iron heads and Torker intake.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind. - Stu Harmon
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Re: What Size Blower for a Gen I street 392 Hemi?
[Re: feets]
#2146087
09/02/16 12:54 PM
09/02/16 12:54 PM
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Joined: Jun 2006
Posts: 5,163 CT
GTX MATT
master
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master
Joined: Jun 2006
Posts: 5,163
CT
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Don't get suckered by boost numbers.
Boost is a resistance to flow. Good flowing heads and a proper cam will show less boost than poor performing components with the same blower and drive on the same bottom end.
I made more power at 8 psi with the Eddy heads and good intake than I did with the iron heads and Torker intake.
Also it is a PRESSURE measurement, not airflow. X PSI with a 6-71 is less airflow than X PSI with an 8-71 because the 6-71 is producing more heat. You can heat air up to create pressure, but you will not make more power (you'll actually make less) because there is no additional airflow. I have a friend with an 8-71 on a 392, lightly ported heads, 240ish duration cam, he made around 650 HP @ 8 PSI and similar torque. Engine has 2 750 DPs on it and its VERY responsive.
Last edited by GTX MATT; 09/02/16 03:34 PM.
Now I need to pin those needles, got to feel that heat Hear my motor screamin while I'm tearin up the street
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Re: What Size Blower for a Gen I street 392 Hemi?
[Re: feets]
#2146110
09/02/16 01:17 PM
09/02/16 01:17 PM
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Joined: Jan 2003
Posts: 24,562 Brookeville, Md
Mr.Yuck
Not enough dumb comments...yet
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Not enough dumb comments...yet
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
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Don't get suckered by boost numbers.
Boost is a resistance to flow. Good flowing heads and a proper cam will show less boost than poor performing components with the same blower and drive on the same bottom end.
I made more power at 8 psi with the Eddy heads and good intake than I did with the iron heads and Torker intake.
what he said...I love when guys talk about running this or that boost. It's just a measure of resistance, you want air flow. From what I understand those old Hemis like boost. A 671 will work, but an 871 will work better and w/ less heat and stress.
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Re: What Size Blower for a Gen I street 392 Hemi?
[Re: B1arno]
#2146450
09/02/16 10:50 PM
09/02/16 10:50 PM
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Joined: Jan 2003
Posts: 14,506 So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,506
So. Burlington, Vt.
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Just depends on where the priorities for the motor are.
If it's primarily a street car and the blower is mostly for "show", a 6-71 will work fine on that sized motor. With a properly designed build, an easy streetable 600hp plus.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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