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Discussion Starter · #1 ·
I see in the issue of Hotrod,feb.2008,they built a High helix 1471 BBC 555ci,at 25% over and with a W/A cooler,283/291 at .050 cam,heads that flowed 420 on the intake,8.3 compression it made N/A 756 hp at 6900,blown made 1178 at 6900.....I alway wondered it 1050 was the max. on racegas,uncooled....And I would therefor think that a SBC. would be limited even more like less then 900..........Like to hear more from you guys....OLDHEAD PS:friends BBC with alcohol made over 1800
 

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what W/A cooler?[just to compare to mine]
i made 989HP on C-12 12lbs of boost A/W I/C with tap water in it.446 cubes.9%OD 8-71.
i dont know if this info helps you any.any Q's just ask.
 

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Discussion Starter · #4 ·
what W/A cooler?[just to compare to mine]
i made 989HP on C-12 12lbs of boost A/W I/C with tap water in it.446 cubes.9%OD 8-71.
i dont know if this info helps you any.any Q's just ask.
I don't know what you mean by"what W/A cooler"? Are you using a SBC?....Do you have any idea how much you would have made without the cooler???I guess you were using racegas????Why didn't you go up in boost???I was so unhappy when I went in 2002 to the dyno with my 871,SBC-400.I had 12 pulley ratios from 21%under to 23% over,I started with 15 under made 680hp on pump 93,And I felt good and looking for 800...I found that 14% over gave 748 hp with racegas,and from that point it was all down hill,19 and 23% over pick up below 6200,but lost over that......A year later I went back with a small street Vorteck YSI hopeing for 850,and had the trouble going over 1000 without a cooler or spinning the blower near redline.....After my first 671 in 1959 and 14 supercharged cars since,But that day at the dyno with the 871 hurt me....Have fun...OLDHEAD
 

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Discussion Starter · #5 ·
I just saw your pictures else where,you have a 440 mopar,Oldhead
 

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in your first post you say 25% over with W/A cooler[water to air]
i did not gain much with 19% over was only 10 lbs more.without the cooler it made 850HP at 5500/896 TQ at 4400.C-12 VP and 30* timing locked out.
 

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in your first post you say 25% over with W/A cooler[water to air]
i did not gain much with 19% over was only 10 lbs more.without the cooler it made 850HP at 5500/896 TQ at 4400.C-12 VP and 30* timing locked out.
 

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OLDHEAD, thought you mentioned on a different board you used nitrous to get over 1000 HP with that YSI.
 

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I don't know what you mean by"what W/A cooler"? Are you using a SBC?....Do you have any idea how much you would have made without the cooler???I guess you were using racegas????Why didn't you go up in boost???I was so unhappy when I went in 2002 to the dyno with my 871,SBC-400.I had 12 pulley ratios from 21%under to 23% over,I started with 15 under made 680hp on pump 93,And I felt good and looking for 800...I found that 14% over gave 748 hp with racegas,and from that point it was all down hill,19 and 23% over pick up below 6200,but lost over that......A year later I went back with a small street Vorteck YSI hopeing for 850,and had the trouble going over 1000 without a cooler or spinning the blower near redline.....After my first 671 in 1959 and 14 supercharged cars since,But that day at the dyno with the 871 hurt me....Have fun...OLDHEAD
Interesting. I would like to know what the results would be with a SBC 6-71 alcohol setup run with 10%- 20% underdriven.
 

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Discussion Starter · #10 ·
I WANT TO THANK YOU ALL FOR THE GOOD INFO!!!!!I will give you more of my storty,The info above was without nitrous,,,,,,In 2002 with the 871 limited at 748hp I then sprayed 50,75,100,150 and 250(93 both nitrous and fuel) I saw 952 at 7000.........With the YSI without nitrous I got 1004 hp at 21# I srayed 50,100 and 150(63n/61f) the belt broke at 6500 with 1120hp,but looked like it at 7000 would be about 1130.......I have been trying 26# lately and picked up 5/10s and 5 mph in the 1/8,BUT Nothing in the 1/4 which i think means "Hot charge" so I bought a Snow W/A injector and its back to the engine dyno very soon,My friend has been trying Snow units on his dyno and picking up 100 to 200 hp is common....Have fun....Oldhead
 

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Discussion Starter · #11 ·
I have tryied at the dyno more then once that going over 15% over drive loses power on racefuel.If you are only spinning it slow at less then 1 to 1 I would think there not much increase with alcohol,but 15 over thats a horse of a different color....The difference in between a 671 and 871 is 5% more boost,at 19# with a 6 would be 20# with a 871.....Dinner is ready......Oldhead
 

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Discussion Starter · #12 ·
Dinner is over now.......You know I have been talking wrong.I have been talking about drive ratios been to fast when I should be say rotor speed.......So here goes,it seems that spinning roots GMC rotors faster then 9500 heats the charge to much and needs alcohol at that speed or faster to cool the charge....Oldhead
 

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Discussion Starter · #13 ·
Oh.by the way,the cam I use is a mild street roller 248-260 at 114 cl.(Custom grind)....I drive my car everywhere even long trips..The heads are Dart 230 flowing 308-234 at .700...The compression is 7.9.........The car is a 1980 Malibu weighing 3570...The convertor is a 2400 street convertor that slips 19%when running the 1/4 mile....Without nitrous a 26# it bested 1.32(60),5.68 at 123,8.99 at 148....with 21# and 150 shot...1.28,5.52 at 129.75,8.70 at 157...........This is driving to and from the track....I have 3 stages of nitrous(400 hp total),2 have not been used yet.......Oldhead
 

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what rpm will the engine spin?
anything past 1/1drive is creating a power loss due to heat.just idling my temps came to 170*if you want to run alky why not.most temps i see on alky blower are still around 100+i am sure the NOS helps under WOT.i dont drive mine onb the street because i have a class A CDL but i retire in 3yrs and plan to change that.
 

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Hey Oldhead, I know you have more experience than I do at this stuff. What kind of hp increase do you think I would see from going 10% overdriven to 15% on my 408sbc 6-71. Spin the motor to 7200 makes 13lbs at10% ,running on methanol. Would it be worth it? Should I try spinning it even faster? JUst wondering before I spend the money for another pulley.
 

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I can teel you this, switching from gas to methanol at 10% over made a huge difference with my engine. I ran two 750 holleys, I made 20 + passes and the best I got out of it was 110mph in the 1/8. I put a bug catcher on witch flows 3300 cfm and switched fuels. The only other thing I changed was my spark plug gap, I changed nothing else. Ive only made 5 passes and i've been 123 mph in the 1/8 with methanol.
 

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Discussion Starter · #19 ·
Only because you are on alcohol,gonig from 10 to 15% would be around 1# in boost,I would think no less then 15 or more then 30 hp...I found that my Malibu at 3570# 50 hp. is worth a 1/10 in et.Sometimes going up with the boost it helps the low end so much that you get more....Oldhead
 
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