Occasional Knocking Noise

[septantrionalis]

Can someone give me an idea on where to start? I hear a knocking noise coming from the engine when I accelerate.  Its pretty loud and doesn't happen all the time -- maybe once a week.  I can get the knocking to stop by letting go of the accelerator then accelerating again.  Honestly, I dont even know if its coming from the engine, but its definitely coming from the front and I can feel it.

My truck is a 74 Chevy K10 with a 350 engine, NP203 tcase, and TH350 automatic transmission.

[zieg85]

Could be that your timing is advanced to much.  Could be a crack in your flexplate as well.  Torque converter loose?

[bd]

Could be that your timing is advanced too much.  Could be a crack in your flexplate as well.  Torque converter loose?

^^^^ This.  If after checking the above you haven't discovered the source of the problem, inspect the crankshaft pulley for cracks and make sure that it's firmly bolted to the crankshaft.  Check all of the bolt-on peripherals (engine cooling fan and pulley, P/S pump & pulley, alternator, etc) and their mounting brackets.  Inspect the motor and transmission mounts.  Verify that the crankshaft end play is in the range 0.002" - 0.006".

[septantrionalis]

Thanks for the ideas.  I will start with those and see where it goes.  It would be much easier to diagnose if it happened all the time.

[FlatBlack77]

Is it a knock you can feel? like maybe a loose engine mount bolt or something.