31/03/2026
Iron Lion build - Holden V8 touring car
Carb flowed
Now we've flowed the cylinder heads we have a very close idea of the carburetor CFM demand from the engine at peak power rpm, by flowing the carburetor we get a very accurate indication of the actual CFM rather than the carburetor's listed CFM.
This carb by part number is listed at 650cfm ,
The CFM demand from the engine at 6500rpm with the CHD ported cylinder head is 805cfm ..... so let's see what the "actual" CFM is...🤔
The industry standard from Holley to flow a carb is 20.4 inches instead of 28 (industry standard for cylinder heads) , we flow each venturi individually with the carb wired wide open, primaries first then secondaries, then run the numbers in the formula as follows
Pri - 208.8
+
Pri - 211.0
+
Sec - 209.5
+
Sec - 213.8
= 843.1
843.1 x .92 (8% fuel)
Actual CFM = 776cfm
This is not quite where we want it (at this stage), however it is very close so will see how much the demand changes after the manifold is added.💪🏁
Once the manifold is ported we will flow the head with the manifold, checking cfm & most importantly velocity, then will bolt carb to manifold and flow as one unit , this will tell us exactly what cfm is available to the engine and will also be able to measure the booster signal..... we want the engine pulling hard on the fuel. 🏁
This just shows that "650" is purely a list number.
This exercise is also extremely good for Speedway Saloon engines where the rules mandate a "600 vac sec" Holley , they're not all the same.... 😉....🤔
Hope this all makes sense 🙏 💪🏁😎
Thanks for looking.
Everything - no exceptions!
Measured - ✅️
Calculated - ✅️
Tested - ✅️
Repeated - ✅️
Guessed - ❌️❌️
