'77 Chevy C-10. Spark plug gap and timing degrees

60thou

Set your points gap using a dwell meter - 30 degrees (range 28 to 32 degrees). Spark plug gap .035"

my first instinct would be too much of a gap in the spark plugs but since you replaced and im asuming you gapped them then your probelem might be the timing chain

Tune Up

Spark Plug

AWSF-42C

Spark Plug Gap

0.044

Ignition Timing

10 degrees BTDC

Firing Order

1-4-2-5-3-6

Distributor Rotation

Clockwise

Valve Clearance Intake

0.014

Valve Clearance Exhaust

0.016

0.042-0.046 is the correct gap for your spark plugs,If it is backfiring now and was not before make sure you were not sold platinum bosch plugs and if you are using factory plugs,then I be looking for a faulty spark plug.Also make sure the firing order is correct.

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.

suppose to be a sticker under hood with info.
if no sticker then try 6 to 10 before tdc.
that is for a 77 model but should be same .
uses same spark plugs. bsf-42 gap..044

The plug gap is .040

Ok here is the meaning of firing order The numbers 1-5-4-2-6-3-7-8 represent the order of wish cylinder the distributor send a spark as it rotates Starting whit cylinder number 1 The distributor will have to rotor on the number 1 cylinder spark plug and the piston on the number 1 cylinder will be at the top So the fuel and air will be compressed and ignited by the spark plug. The next one will be the cylinder number 5 to do the same as the crankshaft and distributor rotate Next will be number 4 then 2 then 6 ? 7 ? 8. You get the idea "10 Degrees" The degrees represent of spark advance You may think gas explode instantly but it actually take a little time So for the explosion has maximum power when the piston reaches the top of the cylinder the distributor send the spark a little ahead of time 10 degrees of revolution is the recommended by the manufacture but that can be adjust buy losing up the distributor clap bolt and manually turn it. In order to adjust that you need a timing gun Than will flash light on the crankshaft pulley (harmonic balancer) and you will see a notch and a series of numbers than represents the timing advance Note If you have not turn the distributor by loosing to button clap bolt I recommend to live it alone and go to you local part store and get the repair manual find the firing order to see wish wire go to wish cylinder Rotate the crack shaft pulley on till the notch is on 0 and see if the distributor rotor is tours cylinder number one. Cars than don?t used distributor do that automatically and constantly adjust the ignition timing by the computer.

The gap on the points to your distributor is .017 or the thickness of a match book.