Has anyone ever had to swap one of these due to it being weak?That swap isn't so bad..but where did you get the new one?My Demon one on the primary side has lost just about all of it's strength and is too soft now.When I activate the pump it collapses the spring a fair amount before it starts to activate the pump giving me a nice dead spot.The swap is obviously not the hard part..takes a whole 15 seconds.Just curious if I should just runs to Home Depot or anyplace like that and match it close enough or is it a specific spring?TIA

 

I've never heard of that happening, at least no on Holleys; those are usually fine even after 30 or 40 years. In fact, that spring is called the "duration spring", precisely because it does just exactly that. It is supposed to provide a controlled delivery of fuel rather than just one massive blast. Also if it wasn't there, since gasoline is incompressible, the linkage would bend if you opened the gas too fast.

If you have a flat spot on throttle tip-in, it's probably because there's a gap between the end of that spring's bolt, and the pump arm; or a power valve with too low of a number.

 

The spring will last a really, really long time. What makes it go slow is a restriction. The restriction is supposed to be the squirters. Bigger squirters will give you more initial 'squirt' but for a shorter time. Smaller squirters will give you a lesser 'squirt' for a longer period of time. Other things to look at, the accelerator pump diaphram getting too stiff or a clogged squirter or squirter passage. Your exact problem happened to my holley recently. Clogged accerator pump passage(chuck of the crappy stock holley gasket mashed into the flowback needle under the squirters). Anyway, like he said above it's not very likely the spring bad. And if it was, you would want a stock demon replacement spring.