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Tye68gto · 03-18-2003, 07:23 PM

I dont really know much about superchargers but i have built my 455 to 12.5 to 1 compression. I wanted to know if it would be posible to run around 5 lbs of boost on the engine or if i must put in dished pistons and lower the compression.

Tye68gto · 03-18-2003, 07:23 PM

I dont really know much about superchargers but i have built my 455 to 12.5 to 1 compression. I wanted to know if it would be posible to run around 5 lbs of boost on the engine or if i must put in dished pistons and lower the compression.

Goatman · 03-18-2003, 07:44 PM

Lower compression. Lots of variables as to exactly how much.

Chance favors the prepared mind.

thirdgen455 · 03-18-2003, 08:14 PM

don't really know about a pontiac, BUT I have a friend how runs a stock IRON headed 427 BBC that runs a 6-71 and 12.5:1 compression. He has had major head gasket problems intill he o-ringed the heads and block and bought high doller gaskets. but all i know is a stock set of square port heads, on a std bore 427 block with TRW jump up pistons the car ran a 9.11 @ 14x.xxMPH and that was with the big pulley. the car does have MFI and runs alky though. but for the basicly stock motor i was super suprised i didn't think blowers worked with big compression, i also didn't think blowers made that kinda power. every kinda street blowers i have ever seen was a BIG POS. thats one badas$$ little 1969 camaro.

http://home.earthlink.net/~saawatson/ my 1983 trans am. PONTIAC POWERED

Goatman · 03-18-2003, 08:30 PM

Two things:

BB Chevy, 5 head bolts per cylinder.

Alcohol.

No comparison.

BTW, there is a member here named Torment that has done pretty well with a roots style blower.

Chance favors the prepared mind.

PONTIAC DUDE · 03-19-2003, 07:51 AM

Your defeating the purpose of a Supercharger with high compression and will end up with less output in the long run.

As you increase boost, you build compression.

Basically it goes this way.

Why run high initial compression to end up with 15-1 with only 6 lbs of boost when you can do the same thing with 8-1 and make 15lbs of boost.
More power and easier on parts and cylinder loading (head Gaskets, etc). That's the whole idea of Supercharging.

Now.............. unless your on Alcohol.

Or Nitro. right Paul.

Build it fast, build it right, build a Pontiac.

http://PontiacDude.cc

PONTIAC DUDE · 03-19-2003, 08:01 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Thirdgen455:
i also didn't think blowers made that kinda power. every kinda street blowers i have ever seen was a BIG POS.

http://home.earthlink.net/~saawatson/ my 1983 trans am. PONTIAC POWERED<HR></BLOCKQUOTE>

I ran an ATI Street Procharger Supercharger, a modified P600B (P1200B),Blow thru the carb deal, unit and ran very very low 10's and at Farmington N.C. last year in the 6.20's (1/8th mile) with no serious problems other then inside belt wear as I was driving a Street blower past what ATI said it would do. They even said I couldn't go that fast either. LOL.
So you see, it's all in the tune up and doing your homework. It's not for everybody as it takes time, money and a lot of testing to Get it right. Back when I started messing with them there was nobody to ask and only 2 models available. The P600 and upgrade with the impeller change to a P1200B (which is no longer available

). I wanted to go into the 9's and they were basically a 12/11 second upgrade deal.
Since then the units have increased in size and output, so you can just buy one for the hp you want and go.

So it can and is being done.

Build it fast, build it right, build a Pontiac.

http://PontiacDude.cc

Half-Inch Stud · 03-19-2003, 12:00 PM

It takes about 100HP to turn my 8-71 at 6000RPM.

It take about 200additionalHP to compress 6PSI boost at 6000RPM compared to normal aspired.

6PSI is only 6/15 of an additional atmosphere.
------------------------------------------------
New Math comming at ya!!! :

455 * 6/16 = 182

455 + 182 = 637 cubic inches.

If your 455 MADE 450HP, then the 6PSI boost will make it feel like a 637 cube motor putting out 637HP...but the ADDITIONAL compressor losses of 100HP lost on blower drive and the 200HP from 12.5:1 make it output 337HP.

a net loss. Or, what P-Dude was saying.
--------------------------------------------
My example:
at 8.3:1,
it will take 57Hp to run the 8-71 at 5200RPM at 15PSI boost.

My 469 would make about 450HP on a good day. So, let's back it down to 400HP on a bad, low-compression day.

15PSI boost is 1 atmosphere. It's like doubling my engine Cubes. 469 x 2 = 938 cubic inch.

400 HP * 2 is a CONSERVATIVE 800HP. I would say the non-conservative upper limit is 938HP. So there is a window of uncertainty here. Let's work with it.

800HP -57 = 743HP NET
938HP - 57 = 881HP NET

This would be the 120%drive or 20%overdrive case.
--------------------------------------------------
The 70% drive case is more streetable for 650HP, which represents my goal...6PSI on pump gas:

469 + 182 = 651 Cubes

Blower Drive loss at 5300RPM and 6PSI boost is about 30HP

400HP + 182HP - 30HP = 552HP
...about as good as when it was 12:1 with dual Quads and Wenzler..to get 11.0 using racegas.
----------------------------------------------
An upper pulley change makes the difference of 550HP Net and 740+HP NET. not bad.

Have a nice day.

Half-Inch Stud

"tbdET/1xxMPH/1.xx 60foot/28"/3.54:1/10"/469 #48/Flat HYD/DualQ-Jets/Offyl/3xx0Lbs
11.00/123MPH/1.50 60foot/29.5"/4.10:1/10"/469 #48/FlatHYD/DualQuad/Wenzler/3250Lbs
12.00/112MPH/1.61 60foot/26"/3.31:1/10"/469 #48/FlatHYD/Q-Jet/Torker/3650Lbs
12.70/103MPH/1.71 60foot/28"/4.10:1/12"/469 #48/FlatHYD/Q-Jet/Torker/3950Lbs"

Half-Inch Stud · 03-19-2003, 12:01 PM

Tyes68gto ,

You now know enough about Supercharging to be calculating/plannning your next engine combo.

HIS

"tbdET/1xxMPH/1.xx 60foot/28"/3.54:1/10"/469 #48/Flat HYD/DualQ-Jets/Offyl/3xx0Lbs
11.00/123MPH/1.50 60foot/29.5"/4.10:1/10"/469 #48/FlatHYD/DualQuad/Wenzler/3250Lbs
12.00/112MPH/1.61 60foot/26"/3.31:1/10"/469 #48/FlatHYD/Q-Jet/Torker/3650Lbs
12.70/103MPH/1.71 60foot/28"/4.10:1/12"/469 #48/FlatHYD/Q-Jet/Torker/3950Lbs"

GTOGEORGE · 03-19-2003, 06:40 PM

Obviously you guys have way too much time on your hands. Turning something simple into brain surgery. Your killing me!

fast1970transam · 03-19-2003, 07:22 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by GTOGEORGE:
Obviously you guys have way too much time on your hands. Turning something simple into brain surgery. Your killing me!<HR></BLOCKQUOTE>

thats why i'm saving my money and then having pontiac dude do my whole setup.Only person i trust

1970 t/a clone g-machne in the works

Torment · 03-19-2003, 09:48 PM

Bill Mitchell used to advertise - maybe still does - high static compression blower bbc's running low boost making 1100-1200hp, they were alcohol motors though. You need to size your blower appropriately to your engine and then spin it in it's efficient range given the fuel you're running - nothing new the people that supply the blower can tell you its desired range. Spin it too fast and it's hard on the blower and everything behind it for nothing, too slow and it's just in the way.

The secret to happiness is not getting what you want but rather, wanting what you have.

Torment · 03-19-2003, 09:52 PM

1/2" inch, 15psi @ 5200rpm with an 8-71. Is this thing going to be stripped or are you stuffing a sock in the exhaust pipe?

The secret to happiness is not getting what you want but rather, wanting what you have.

Tye68gto · 03-19-2003, 11:42 PM

Thanks for all your help. I guess that i will tear down the engine again and put in dished pistons. But also have any of you guys ever run a centrifical supercharger. Are they any better or worse than the other designs.

Goatman · 03-20-2003, 06:31 AM

I was going to, then decided to go with turbo's. Pontiac Dude has run one.

I believe them to be capapble of much more HP than the roots designs, on gasoline.

Chance favors the prepared mind.

Half-Inch Stud · 03-21-2003, 10:25 AM

Torment said:

"You need to size your blower appropriately to your engine and then spin it in it's efficient range given the fuel you're running "
-------------------------------------------------
YESH!..That is key to seeing any ROOTS advantage.

Otherwise, Turbos or Screw rotors will look better.

My windmill is low-inertia and loosey-goosey (no teflon strip sealing) for the purpose of even less boost at idle, and less HP pulley/drag losses at full RPM. Helps to compress (de-pulse)the Roots outlet before letting it into the manifold distribution.

I thinks the Street/Strip tradeoff favors Gasoline-Injected Roots with 3-lobe regular Helix Rotors...while competitive drag race favors Really big Screw rotors, with Alcohol injected Nitro-Methane. Both are extreme huh.

I play with cheap parts.

Half-Inch Stud

"tbdET/1xxMPH/1.xx 60foot/28"/3.54:1/10"/469 #48/Flat HYD/DualQ-Jets/Offyl/3xx0Lbs
11.00/123MPH/1.50 60foot/29.5"/4.10:1/10"/469 #48/FlatHYD/DualQuad/Wenzler/3250Lbs
12.00/112MPH/1.61 60foot/26"/3.31:1/10"/469 #48/FlatHYD/Q-Jet/Torker/3650Lbs
12.70/103MPH/1.71 60foot/28"/4.10:1/12"/469 #48/FlatHYD/Q-Jet/Torker/3950Lbs"

Half-Inch Stud · 03-21-2003, 10:26 AM

Do Nitro-Methane engines run turbos?

Half-Inch Stud

Goatman · 03-21-2003, 02:16 PM

I believe Mr. Palbykin is trying that out at this time.

Chance favors the prepared mind.

Half-Inch Stud · 03-21-2003, 05:29 PM

Mr. Marty P-Beacon....: trail blazer

GTOGEORGE · 03-21-2003, 10:19 PM

I have a question do you guys ever raced your blower cars at the drag strip or do you just keep them in the garage and give out information?

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