3ltr GM - new carburettor

[High Flyer]

Hi Guys -
After having trouble with with rough/low power running and fuel flow issues, last season, we have fitted a new mechanical fuel pump (and having taken the old pump one apart it certainly needed replacing) and a new carburettor, having fitted everything the engine ran horribly, the carb came with a alternative set of jets, which were then fitted, and the engine now runs smoothly and revs better than ever.
My question is what were the alternative jets, and why did they make so much difference.
Regards: John

[mmwjr]

Can’t really answer your question as I’ve not seen a carburetor come with alternate jets other than performance carburetors. Typically they are marked. The difference between then is the size of the passage drilled in them which controls fuel flow. The original jets may have been too rich, bigger hole.