DragRaceResults.Com    Bracket Talk    Bracket Talk Forum  Hop To Forum Categories  Tech Talk - by Abruzzi    stumble at the hit-on alcohol
Go
New
Find
Notify
Tools
Reply
  
stumble at the hit-on alcohol
 Login/Join
 
DRR Trophy
posted
stumble at the hit-on alcohol, 750, 460 bbc. low compression 10:1
All, I have a bad stumble at the hit with this simple combo, i have large squirters and 50cc pumps both ends. Car runs good except for this, I drilled the rear squirter to a .065 drill. helped a little im out of squirt at that point. any ideas? thanks
 
Posts: 22 | Location: ohio | Registered: August 15, 2017Reply With QuoteReport This Post
DRR S/Pro
posted Hide Post
Drill them both out!

Sounds like your to lean on the idle side which compounds the problem, richen that up too.

If you can raise the rpms before to stab it, this will also help.

Anything you can do to reduce the initial load on the motor at the hit will help too, smaller manifold, looser converter, more gear, smaller carb will all help
 
Posts: 2163 | Location: Tewksbury, MA,USA | Registered: November 03, 2000Reply With QuoteReport This Post
DRR Top Comp
Picture of Curly1
posted Hide Post
Blow out your air bleeds and then you may have to fatten idle mixture some.


https://postimg.cc/gallery/np3zpruo/
"Dunning-Kruger Effect"
-a type of Cognitive bias where people with little expertise or ability assume they have superior expertise or ability. This overestimation occurs as a result of the fact that they do not have enough knowledge to know they don't have enough knowledge.

Before you argue with someone ask yourself, "Is this person mentally mature enough to grasp the concept of a different perspective?" If not there is no point to argue.

4X NE2 CHAMPION. 2020 TDRA NE2 Champion
 
Posts: 4282 | Location: United States of Texas | Registered: April 02, 2011Reply With QuoteReport This Post
DRR Sportsman
Picture of 57 Vette
posted Hide Post
Easy fix, is to turn out the idle mixture screws to richen the mixture. And if that does not fix it,try a smaller air bleed.Also make sure you have enough initial timing and the dist is locked out.

IHRA ACDELCO Canadian Nationals
Top/et Iron man Champion Wink
57 Don Davis Super Gas roadster Cool
SDPC 582 Head Hunter on Alcohol

This message has been edited. Last edited by: 57 Vette,
 
Posts: 268 | Location: Toronto Ont/Surprise AZ | Registered: August 18, 2003Reply With QuoteReport This Post
DRR Trophy
posted Hide Post
All good advice mentioned but i wanted to add my recent experience. I had a persistent stumble where nothing I tried helped. Eventually found the pump arm springs (the ones where you adjust pump arm clearance) would compress as they were pushing the lever of the accelerator pump not giving the direct pump shot needed at the hit. I fixed it by further compressing the spring (made stiffer) using multiple small washers as shims.
 
Posts: 4 | Location: Nc | Registered: August 11, 2017Reply With QuoteReport This Post
DRR Sportsman
posted Hide Post
Flip it upside down and see how much transfer slot is exposed before doing all the tweaks and drilling.
 
Posts: 479 | Location: here | Registered: February 12, 2006Reply With QuoteReport This Post
DRR Trophy
posted Hide Post
[QUOTE]Originally posted by Curly1:
Blow out your air bleeds and then you may have to fatten idle mixture some.[/QUOTE)

What he said
 
Posts: 4 | Location: Melbourne, Australia | Registered: March 29, 2012Reply With QuoteReport This Post



DRR S/Pro
Picture of Eman
posted Hide Post
quote:
Originally posted by team:
Flip it upside down and see how much transfer slot is exposed before doing all the tweaks and drilling.

Do this first. Check and adjust your pump arm springs. If needed change pump cams.
 
Posts: 1570 | Location: E TN | Registered: February 13, 2009Reply With QuoteReport This Post
DRR Top Comp
posted Hide Post
First thing you do to figure out if it's rich or lean, is turn all four idle mixture screws to one turn out. If that makes the stumble worse, you know it is lean, as long the stumble improves when you turn all four idle mixture screws to a turn and a half out.

If it's lean go to a smaller hole size idle air bleed. No stumble with the mixture screws turned out one and a half turns, or less down to one turn, is Ideal.
 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post
DRR Sportsman
Picture of FootbrakeJim
posted Hide Post
Lot of good advice on here.
Man, that is such an undersized carb for that engine, it should have tons of vacuum and should not have stumbling issues unless something is way out of whack on your carb.
Was it converted from a gas carb? And by who?
Check float levels, then check quality and quantity of shooter squirt, (with engine OFF).
You should be getting a massive shot on any alky carb. My 468 has a 1050, shooter nozzles are .110" And that spray should begin immediately with first movement of throttle.
Is your primary/secondary linkage progressive, or 1:1? I.E: Do primaries open first, (progressive), or do all 4 blades open equally at the same time (1:1)? If progressive, you generally need more pump shot on your primaries.
What color pump cams are on it?


Dan "Jim" Moore
Much too young to feel this damn old!!
 
Posts: 1101 | Location: Farmersville, TX  | Registered: December 05, 2002Reply With QuoteReport This Post
DRR S/Pro
Picture of banjo
posted Hide Post
Is this a new issue?

Check the rubber check valves in the squirter pumps, it will still squirt, just not the full volume.


Bill Simpkins
74 Nova
SBC 406
3240 pounds
Speierracing heads

60 1.27 (10/16)
1/8 6.03@111 (10/16)
Best 9.87@131 on the rev limitor 1 Feb 2013


nova

quarterpanelview

wheelie

FTI Converter
www.speierracingheads.com

 
Posts: 1837 | Location: San Angelo | Registered: March 07, 2005Reply With QuoteReport This Post
  Powered by Social Strata  
 

DragRaceResults.Com    Bracket Talk    Bracket Talk Forum  Hop To Forum Categories  Tech Talk - by Abruzzi    stumble at the hit-on alcohol

© DragRaceResults.com 2024