help - excessive backfiring after rebuild

[chris-stockton]

hi guys,

i hope someone can help, just took my westfield v8 out for its first drive post engine rebuild and its really not happy.

Seems to be ok on idle and part throttle but as soon as you get to half throttle or more, you get an enormous backfire from the exhausts.

So what could this be?

only things i can think of that were altered vs before we as follows:

head skimmed by v8d (composite gaskets)
previous crower cam correctly dialed into 104 deg (was on std gear)
ngkbp6es instead of ngkbpr7es
metal canister fuel filter replaced by plastic inline next to carb.


what should be my hit list to start checking, its never done this before.

cheers

[JP.]

What ignition system ??

What carb ??

[chris-stockton]

hi, its a webber 500 (around 1 year old) just checked and float chamber area seems ok,

ignition is MSD coil and amplifier