Weber tuning on 427 engine

[Hannes]

just fulfilled my boyhood dream and bought a 427 with weber 48IDAs. Unfortunately I have a real problem in getting the webers tuned.

The car previously was used in South Africa and I am not sure that here in Austria the current setup of the webers can work at all due to climatic differences.


After trying a few different jets, here is my cry for help:

can anybody recommend a good basic setup for the webers for a 427 engine, which is supposed to produce 425 hp ? unfortunately nothing is known about the exact details of the engine (cams, compression etc.).

with the original jets it ran way too rich backfiring all over the place and fouling the spark plugs real fast.

with a new set of leaner jets I got it to run well at idle and until about 3000 RPM. then its starts to backfire in all directions again, even worse than before. Going higher with the RPMs it stops backfiring but does not produce a decent power output and seems to run too lean.

currently there are 40 mm venturis installed.

any help and hints would be much appreciated.

with kind regards from Vienna

Hannes Winkler