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

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

Blow out your air bleeds and then you may have to fatten idle mixture some.

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.

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This message has been edited. Last edited by: 57 Vette,

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.

Flip it upside down and see how much transfer slot is exposed before doing all the tweaks and drilling.

[QUOTE]Originally posted by Curly1:
Blow out your air bleeds and then you may have to fatten idle mixture some.[/QUOTE)

What he said

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.

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.

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?

Is this a new issue?

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