whats wrong with my engine?

[SRlew]

right for a while now its been running rough. its revs fine up to 2k the just doesnt want to rev upuntil like 4k then after 4kish its fine,

in the bad range of rev it backfires and jumps real bad. engine is t40's, piper 285 cam on c14se gas flowed head.

any ideas?

cheers lew

[Adam]

Is your ignition timing spot on?
Also check the cam timing.

Might be worth changing spark plugs, leads and dizzy cap too

[mowgli]

could be an advance retard thing or the fact that the autumn weather is upon us causing carb icing.

[SRI crazy]

did u get the carbs set up an adjusted properly, did u use a timing pulley for the cam?