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Pontiac - Boost Turbo, supercharged, Nitrous, EFI & other Power Adders discussed here. |
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#41
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I believe down the road I'll probably change to a different gear maybe
when I put this motor in the other firebird it was intended for. As for now I'll just do a converter change and see if that works. Lot of the guys I know that run blowers said they ran a lower 3-series gear and some of them where spraying too. Sounds like you got a handle on yours. Good luck with it. I'm going to change mine tomorrow. GT. |
#42
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I'm having trouble making sense of your numbers. I ran a 6-71 blown iron 400 engine in my blown-alky puller for awhile; saw 8,300 RPM on most runs, with no more than 12 PSI boost.
You talk about a "mild" cam- the one I used in the puller was ground in 1958 by Harvey Crane- lift was only .478" and was not a "blower" grind.
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Anybody else on this planet campaign a M/T hemi Pontiac for eleven seasons? ... or has built a record breaking DOHC hemi four cylinder Pontiac? ... or has driven a couple laps of Nuerburgring with Tri-Power Pontiac power?(back in 1967) Last edited by Jack Gifford; 06-29-2017 at 01:11 AM. |
#43
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Bluegoast and George both have 8-71 BDS Superchargers, as does Jim I believe.
Might be some of the difference there. Today, Jack, if the cam does not have .800+ lift, it is a "little camshaft" vs your .478" lift deal. So don't pay too much attention to the "Mild Cam" label used today. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#44
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Sounds mild to me...230/240@.050 flat hydraulic on a 113ls from his earlier post...
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1969 GTO, 3370 lbs, 10.5” tire... 07/31/21 Norwalk 9.42 @ 142 1/4, 5.95 @ 115 1/8th mile 3400 lbs...535 with Junk dinosaur Eheads |
#45
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Agree, It is a basic RA-IV type camshaft as far as duration, at .050"
Even with the events moved around a bit. At one time people called the RA-IV cam a "performance cam". .480" lift with a 1.5 rocker .520 lift with a 1.65 rocker Bigger than Jack's camshaft specs he posted. So your post basically proves my point. You called it Mild too. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#46
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Quote:
GTO George |
#47
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Listen to the Man.
Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#48
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Ok here's my two cents worth take it how you like. Back in 82 I ran a 400 cast rods, cast pistons an HO racing cam similar to the 041 cam spec's. 72 HO round ports which gave 7.2 compression. I ran a 671 blower at 12% under driven for a max of 7 PSI of boost. With 4:10 gears shifting the manual trans at 6000RPM's it went 10.50's in the quarter in a 3500LBS car. Later the same heads, cam and blower setup on a 455 with 8.5 compression, 4.10 gear and a manual trans driven 1.1 making 8PSI of boost. But in a Grand Prix weighing in at 4500LBS it ran 11.40's at 117.5 MPH. You have an 871 blower driven at 3% over with 7.8 compression this works out to 15.5 to 1 total compression! Way to high for pump gas! You are detonating at full boost and probably won't ever hear it with the blower whining. Also two 750 carbs are to small for an 871 with this much boost. You are more than likely running out of fuel at high boost hence the falling on it's face at 900ft. Also as mentioned the converter sounds very loose for your combo. With a blower setup running on pump gas never go over 12.4 to 1 total compression. You should run the blower at 12% under driven for you combination of part's unless you use 112 octane race fuel or higher but the carbs will still be marginal at these boost levels. I believe between the detonation, fuel starvation and converter your fighting a loosing battle that Nitrous will only exacerbate. You don't need forged parts if you run a smart conservative combination, sure they offer extra insurance but definitely not required. Hope this helps and good luck.
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#49
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Great Info alloy indian and 10.50s and 7 psi you were having a lot of fun.
So how many years did you run that combination in the 3500 lb car? Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#50
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Thanks,
That cast engine is still together but the blower is long gone. I drove this on the street from 82 till 89 when I parked it. You see the police didn't fancy that big huffer sticking through my 72 F-body's hood. Can't understand why myself I thought it was bitchen! |
#51
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Yeah, you might have a chance to catch up to the turbo car.
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#52
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Never raced and lost to a turbo car!
GTO George |
#53
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My compression at max boost is 12:6:1 I'm at the edge for pump gas.
The carbs don't say any where what the size might be They might be 850's got to check into that. I changed the converter today man what A difference that made. We have new black top around here so I got after it even though the road was damp and short shifted, The guy's Told me that the front wheels were about six inch's off the ground. It's like a totally different car. Can't wait to get back to the track. I guess I'll find out on drag weekend, we leave thurs. So I'll be at Stanton on the 7th and Martin the 8th. I'll let you know what happens. I can't thank you guy's enough for all the info and steering me in the wright direction. The car drives so much better and feels like it would pull al the way to 200 mph if I wanted. I'll know more when I get to drive it more, Right now it's raining here. GT. |
#54
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This is the last I will say about this. 15 Pounds of boost, a 400 and 7.8 compression at 6000RPMs works out to 15.5 total compression. At 8 pounds of boost you would be at 12.5 total compression with this combo. Good luck and have fun with your car that's what it's all about.
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#55
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Quote:
GTO George |
#56
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Brought up the build pics and video of my blower motor.
It's on the race section (New Power Plant) Thought you guys might want to see it again. Also tells about the motor. GT. |
#57
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Drag Weekend
Well heading out tomorrow for drag weekend.
Hope the car works right with the new converter. Should be fun anyway, That's what it's all about. GT. |
#58
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Good luck!
__________________
John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." – Socrates |
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