Re: New motor with previous set up bolted on. Wondering about compatibility between c
Did you check the throttle travel? With the control in throttle only and pushed all the way forward is the carb throttle lever all the way back?
It could also be the timing advance is not kicking in. I cannot remember if you had mentioned checking all that out after your re-rig. I would want to check the timing advance, if it is not kicking in to 30 degrees or more total between 2200-3000 rpm then 3500 is about all it will be able to get to.
If the carb is getting full throttle travel and the timing advacne is working properly then it sounds like the secondaries are not opening soon enough or maybe at all. The opening rate is controlled by the spring that works agains a diaphragm in the vacuum secondary pod just to the left of the choke. Sometimes the rod from the bottom of the pod is not connected back to the secondary lever if it has been removed to change the spring o for a rebuild. There is a very small lock ring that keeps the bottom of the rod poked thru the lever. If you can get a full on side view of the bottom of that pod then follow the rod down you will see what I am trying to describe. Some times the diaphragm may not have been seated properly when the top was tightened down and there is a leak there. The pod gets "Vacuum" from an internal passage from the primary venturis and that is what draws the diapghragm against the spring and moves the rod. There is a very small thick rubber gasket in the throttle body that the pod hole seals against. If that seal is not good then the pod will not get good vacuum. I am not suggesting it be reomved, I am jsut describing the workings for further divination of possible causes of your problem. The choke housing has to be removed first to get to the pod mounting screws, so be sure you really need to take it off as we all know one thing can lead to another.
It could also be the timing advance is not kicking in. I cannot remember if you had mentioned checking all that out after your re-rig. I would want to check the timing advance, if it is not kicking in to 30 degrees or more total between 2200-3000 rpm then 3500 is about all it will be able to get to.
Regarding the secondaries, it could be that they open way too soon and the engine can't catch up. This can happen if the spring was left out, not very likely. This is easy to "listen" for. If at throttle wide open and engine at the 3500 rpm or so under load of course, move the throttle back briskly but not radically to just above idle, at least less than 1/4 throttle. Listen for a whistling and whooshing sound that changes pitch, that would be the secondaries returning from being open. If you have not heard that then disregard this as a probability. That noise usually indicates the secondaries are opening at too fast of a rate. Kind of a Holley thing for tuning.
Like I have said before, mine runs like a striped ape and I know yours can too.
By the way, the specs you mention are exactly what I turned up when looking my carb# up. Interesting that this same carb is what was specced out for the Shelby Cobra 427. It comes with a warning that the secondary spring is very light, and that it can start opening when the choke is all the way closed, just some trivia for the day.
Thanks to Maclin and others, I have corrected fuel delivery potential causes and ruled out being over propped.