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#1
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Hood Scoop Slowing Down Car
Have a real brain teaser here. Have a 1000 cfm APD carb, snorkel hood scoop, no air pan or anything to seal carb to scoop. Car is footbraked and more often than not has a stumble AFTER I leave the line. Car initially leaves fine.
Last weekend the top of the snorkel broke off down track on the first run (after the usual stumble after leaving). 1.58 60ft The rest of the day the car was amazing leaving the line and 60 footing. (1.54-1.55) Has never been that clean and crisp consistently. We didn't think anything of it. The air was fair (for us 3000 is good air) so we thought maybe it was just that. Next weekend we replaced the broke snorkel with a new one and went racing. Air was bad to start the day (3600 at 9:30 am) Car stumbled two passes back to back. (1.62-1.65 60 ft) Got me thinking the hood scoop was doing something. Finished the next 2 rounds getting beat with an inconsistent car. 1.635 60 ft then a 1.654 60 ft. Took the hood off for a time only. At this point the air was 4400 ft. Car went 1.606 in the 60 ft. did another pass to be safe and this time car went 1.598. To me this says the car is fat down low in the first half second of the run and liked the unrestricted air with no scoop/hood. What's the first change? Seal carb to scoop? Different scoop? pump cam and squirter change? |
#2
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Quote:
Funny you post this, I’m going to try to run my car this weekend without a hood as well, I have a 1450 carb and I have alot of open area for the carb to suck in hot air, I would try what I’m going to do, try a clear lexan hood scoop with no hood and see how you do. Sent from my iPhone using Tapatalk |
#3
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Bowl vent tube slosh/siphoning from direct flow of scoop air, absent when it's gone?
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'65 Tempest 467 3650# 11.30@120.31 |
#4
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If it puffs black smoke on the leave it's fat ifnot it's probly a lean condition.
Just my thought GT |
#5
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I did a bunch of testing on the snorkle scoop back in the 70s.
Do you have a "bleed vent" at the bottom rear of the snorkle scoop? 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. |
#6
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No I don’t believe I do
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#7
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. Here’s the hood before new snorkel was put on. Hole size okay?
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#8
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I noticed when the scoop was off I had a splash of fuel on the windshield on every launch. Sure it’s from the squirter
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#9
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Could be. Could be out the vent tubes, and with scoop on it goes down the carb instead of on the windshield.
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'65 Tempest 467 3650# 11.30@120.31 |
#10
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Lower floats a hair maybe? I can just see the top of fuel at the very top of sight window … just barely
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#11
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I wouldn't if the engine is happy otherwise. A simple test is make some extensions out of fuel line and see if it helps do away with the stumble.(scoop on)
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'65 Tempest 467 3650# 11.30@120.31 Last edited by Scott65; 05-08-2023 at 11:04 PM. |
The Following User Says Thank You to Scott65 For This Useful Post: | ||
#12
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Here’s the carb I’m running
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#13
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That looks like the vent tubes should be adequate. How close do those tubes come to the scoop when it's on?
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'65 Tempest 467 3650# 11.30@120.31 |
#14
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About 5 inches I’d say. Carb barely sits under the hole in the hood.
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#15
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I'd say it carb needs sealed to the scoop?
Too much (bad) air movement around the carb with it being open like that? Plus the real benefits of the scoop aren't being utilized with it not being sealed to carb.
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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 |
The Following User Says Thank You to johnta1 For This Useful Post: | ||
#16
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Quote:
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. |
#17
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Quote:
GT |
Reply |
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