Plug gap setting for chev 5.3L - 2000 Chevrolet Silverado 1500

As Long as you gapped correctly, you may have a timing problem.

Olds engine .060 chev engine .045 both with HEI ignition.

On the 96 Chev Blazer 4.3 L V6 engine the recommended spark plug gap is---- .060"

SPARK PLUG .043" GAP

first remove number 1 spark plug, this is the front first plug on the driver side.put your finger over the hole and have someone bump it over until you get compression blowing your finger off the hole tell them to stop. then look on your harmonic balancer and line up the notch on balancer to the wide gap on the pointer. when this is lined up your then on number one compression stroke.

You have a 1986 454 engine with an old style breaker point ignition distributor, GM has not used a breaker point ignition for their V-8 engines since 1974, is that an older distributor or something after-market?

The ignition points dwell angle for that engine should be set at 29-31 degrees dwell (a dwell meter would be the most accurate way to set the ignition points), or a .019 in. point gap.

The spark plug gap for that engine would be .035 in. and the timing should be set at 10 degrees before top dead center.

did you make sure the gap size was right and not just put them on without checking??

I'd say probably .060 but see sticker on rad support or underside of hood to be sure.