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Weird puttering sounds accelerating up hill


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Hey dudes. So I have a 76' datsun 620 w/ around 220,000 miles on it and engine has been acting a little weird recently. I was driving it up a hill and the engine was making popping sounds and losing power every time I pushed on the gas pedal. When accelerating on flat ground, everything is fine but uphill, the car was dying. also before this happened, the speedometer started acting crazy and spinning all over the place. Not sure if they're related but something is definitely up with my lil' hustler. Any thoughts would be greatly appreciated as to what's going on. Thanks, Dave

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Popping sound is usually a backfire through the carb and is quite noticeable. This can be caused by the following...


1/ A bad intake valve seat, damaged or bunt valve or possibly not fully closing because the valve clearance is not set.

Check and set the valve lash to proper spec. A leak down test will confirm a hissing sound from a leaking valve. If the sound is from the carb an intake valve or seat is bad. If from the tail pipe its an exhaust valve.


2/ A blown head gasket between two adjacent cylinders.

A compression test will sometimes show two adjacent cylinders with low values. A small leak may not be big enough to show up.


3/ Spark jumping to another wire and firing the wrong cylinder.

Inspect all wires and ends, cap and rotor for obvious damage. Clean with WD-40 and a rag to remove grease and dirt. Look for carbon tracking which looks like a scratch or burnt path where the spark has found a path to arc across. If in doubt replace them all.

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