Re: Edelbrock 1411 vs 1407
The springs essentially play an up/down tug of war with the manifold vacuum to determine what diameter of the rod is pulled into the jet. Take for instance a .070x.037 rod. Under idle/cruise, the vacuum is high and pulls the the .070 diameter of the rod down into the jet.(to regulate fuel flow for cruise mode) Under WOT, manifold vacuum goes to zero and the springs are are now free to pull the rod up out of the jet, exposing the .037 diameter of the rod in the jet.(to promote more fuel flow for power mode) The transition from cruise mode to power mode is where the spring choice comes into play.
What happens in a mid-throttle stumble is the spring does not overpower the vacuum fast enough and it keeps the fat part of the rod in the jet too long; essentially delaying the delivery of fuel when you enter the power mode.(hence, the stumble) With a stronger spring, it overpowers the vacuum sooner and there is no lapse in fuel flow from cruise to power mode. As taken from the edelbrock tuning manual, the spring strengths are as follows: (from weakest to strongest)
Blue 3" staging vacuum
Yellow 4" staging vacuum
Orange (stock) 5" staging vacuum
Pink 7" staging vacuum
Plain 8" staging vacuum
That said, the problem is not always the spring. If the problem persists, even with the strongest spring, the problem is related to the metering. If that is the case, I would try to go more rich in the cruise mode. (smaller diameter for the first number.. ex: .065x.037 vs .070x.037)
'69 - 408sbc: 11.70@116mph
10.7:1, 65cc AFR 195 Eliminators, Comp XR288HR, RPM Air-Gap, 950 Street HP, Dynatech 1-3/4 Stepped Headers, 3" Magnaflow X-pipe Sys, MSD Dig 6AL, 200-4R (2800 stall), 8.5 10bolt 4.10 eaton 30spl posi /Cal-Tracs
Last edited by xAerox; Apr 27th, 10 at 08:48 AM.