I'm not very familiar with the internal differences of the Edelbrock VS the Holley, Rochester, or Carter, but I'll add my general knowledge two cents worth anyway. :L
This is the order of what I would check:
1. Look for an in-line canister type fuel filter, I can't recall where they were located, I think it may have been in the engine compartment, just prior to the fuel pump. Find it, replace it.
2. By all means, replace that clear fuel line with an approved line, that clear plastic line is a fire waiting to happen. It is not your performance problem, but a safety issue.
3. Check to see if there is an internal filter where the fuel line enters the carb. Holley, Rochester, and Carter carbs all had them, Edelbrock might also. If it has one replace it.
4. If you have replaced all the above filters, you should have a clean unimpeded fuel flow at all RPMs, if not then the next check is fuel pump pressure and flow. Check the pressure with a gauge, and the fuel flow according to the service manual. If the flow and pressure are low, determine if it is the pump, or if the fuel is not reaching the inlet side of the pump.
5. Since the in-line canister was found and replaced (I hope) then you could have poor fuel flow from the tank to the pump.
There is a fuel strainer located inside the tank on the fuel pickup/sender unit. This was made of nylon mesh, and they can become clogged, especially if there may have been high water content sometime in the history of the car.
5a. Drop the fuel tank, remove the sender/pickup unit, and check the fuel strainer carefully. Some strainers may be replaceable if they were the type that were retained only by press fit.
If the strainer looks the least bit suspect replace it while the tank is down.
5b. If the strainer looks OK, check the lines that come out of the tank for deterioration, inside as well as outside. Also look for possible rust deterioration of the steel line coming out of the tank as part of the pickup/sender unit, and the lines running the length of the car. remember, the line from the tank to the fuel pump are not pressure lines, they are suction lines, and any minute pinhole(s) will cause an airleak, and a resulting airbubble in the fuel on it's way to the fuel pump. This can cause a reduced fuel flow and insufficient fuel/pressure under high loads when it's needed the most.
6. Once you have satisfied yourself that the fuel flow is OK, and the problem persists, I would check the exhaust pipes for internal collapsing. Way back in the 70s GM was having problems with the double wall exhaust pipes collapsing under the newfound heat of the leaner burning and cat connverter engines. We found it quite by accident on many GM cars, not just Chevys. It will drive ya nuts because it doesn't feel like an exhaust problem, and occurs only under load at high throttle application.
This is really lengthy so I'll end here.
vettepilot
