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#1
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No top end mph
I took the 1050 Holley and restrictor plate off and replaced with an 850 Holley. I lost finish line mph. 60;s are 1.33 with an 1/8 of 6.30/107 but only manage 9.9 barely breaking 132mph . Do you think it's the carb being small or should I look at a gear change? Car never had high mph even with the 1050.
I have a 4.10 gear and 30" tire. Shift at 6400 and cross the line at 6800. I run a 10.00 index and am tired of having the lowest mph. I am always looking behind me to see where they are. Would like to be around 135mph. Only ran it all out thru the 1/8 once with the 1050 and ran a 6.04/111 with a 1.29 60'. Didn't have enough gear to run it thru the 1/4. |
#2
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Do you have data logging? To me It looks like to much convertor slippage.
Stan
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#3
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No data logging. Calculator shows just about 9 percent slippage. Afraid if i put a 3.90 or 3.73 slippage will go higher,
I have an ATI MRT 8" converter stall right at 5000. I leave at 3800 with a trans brake. |
#4
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You should have not done that type of testing without having a vacuum gauge hooked up to view in front of you when making a pass.
Having such would have clearly shown if the Carb is too small. With any flat out race motor if your approaching your shift point and the gauge is reading 3/4" of Hg or over then your Carb is too small.
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I do stuff for reasons. |
#5
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Quote:
I have always run a manual trans. So I can only go by what some others have told me. Using your car as an example they went to a 4.33:1 saw an increase in MPH and no increase in RPM. Maybe give ATI a call and see what they think Stan
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#6
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The reason for the carb change was to get rid of the restrictor plate. I had a 1050 with a 1.550 restrictor plate under it. The 850 throttle plates are 1.75 and have no restrictor plate. I notice with the 850 60's and 1/8 mile is better and more consistent than the 1050 with the small restrictor plate.
Last time out 1/8 mile times varied .004 over 5 runs. I used 1/8 mile because of hitting the brakes in eliminations. Figured it can't have any more vacuum than the 1050 with the restrictor plate at wide open. |
#7
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Tire size? Just a thought...
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If you cant drive from gas pump to gas pump across the map, its not a street car. http://s207.photobucket.com/albums/b...hop/?start=100 |
#8
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Quote:
4150 carbs are always going to react better. More consistent 60 foot times over a 4500 carb. The way to go for bracket racing. |
#9
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4150 850(1000HPs) have 1.75 throttle blades.
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Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
#10
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I think the blades are stamped 180 but are 1.75" diameter?
(been over 25 years since I looked at one)
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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 |
#11
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have you had it on a dyno to find out where max power is being made -- what rpm.??
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#12
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Quote:
I just remembered drilling a 1/8" hole right through the "8" back in the day. Wonder why they do not have the actual diameter stamped on them ? Has to be some reason. |
#13
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I think they are a part number or ID number.
Seems like the 750/800 had maybe 179 stamped number? (still been a long time since I saw mine)
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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 |
#14
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Never had it on a dyno. Been about 8 years with the same combo. Tried different shift points and likes 6400,. I notice the smallest head wind slows the car down, Not being the most aerodynamic body style. The 2 times I took it out had some low wind, I think this might be some of my problem since I installed the 850.
It did mph a little better when I was running a 30" slick. I switched to a 30" radial 2 years ago. The radials hook a lot better and are more consistent. Not knocking slicks, just radials work better with my car. Stock suspension and 3400lbs. |
#15
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Mph is horsepower.
Mph is down, hp is down. Going from a 1050 to 850 will slow you down. It may be more consistent, but you will slow down.
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1978 Pontiac Grand LeMans.......out next year Previous - 2001 Jerry Haas-built P/S Grand Am - former WJ car, Hoffman Racing 535" IA2, Tiger Heads/Intake, Single Dominator, PG Best ET: 7.776 @ 175.94, 1.096 60', 2375 lbs. |
#16
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To many unknowns here-- as in head flow , engine size ect.ect. I suspect the 6800 rpm finish line is well past peak HP. just a thought.
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