Leon, I am afraid I am going to be a bit long winded now... Apology in advance...
Attached are two screen shots of an excel spreadsheet we assembled for the car we are building. Given torque as a function of RPM (what we expect to get out of our build) and the gear ratios w can assemble optimum shift points and can plot HP as a function of Speed (assuming I am racing the car).
Please take a look at the spreadsheets ---
Since I know my tire diameters, rear end gear ratio, and transmission ratio, and can look up what other people have measured (torque vs rpm) I can take a look at what the optimum shift points are for my car. The first spreadsheet shows (from right to left) RPM, Torque, HP, then left to right, the speed the car would be traveling if it were in 1st gear, 2nd gear, ... 5th gear by knowing the speed and Engine RPM then looking up the available HP (in the right).
First thing, notice the knee in torque at 5500 RPM (I expect the engine I am building will not knee until 6000 rpm, but I am being conservative here). The loss in Torque causes a loss in horsepower at 6000 RPM. A wider torque curve would greatly improve overall HP.
Your car has webbers ( a 6 pack right? ) Well your torque curve comes up much faster in the low end then mine does using SU carbs. You can model this here also.!
Lastly, lets take a look at the last plot. In this plot I plotted the available HP as a function of RPM you can see the HP dips / each represents a shift point. In addition, I compared the car as is with a different rear end (one with 4.11:1 gear ratio). Notice the low end HP improvement!
What happens if I swap out the stock rear end for one which has 4:11 gears. Notice we get 160HP at the tires at 20MPH in first gear (4:11 gears) instead of 35MPH at first gear (3.5:1). This little change should make a BIG difference to quarter mile and off the line times. Again, note your webbers have more torque at the low end then my SUs so your results may be difference. Which means, if I want my car go go faster, the easiest thing to do is to change gear ratios instead of farting around with trying to eek out another 5HP.
This is a long winded way to say:
- The L24/26/28 are magic motors and one thing they have is their ability to be perfectly balanced throughout all RPM. Take advantage of it!
o balance your motor
o understand how your modifications will effect torque
- Take top down approach to building your car and understand how your car will respond to each modification you make
o sometimes your best modification are gear ratios
If you want a copy of my spreadsheet, send me an email and I'll forward it to you. James.Canyon@gmail.com