1968 Tapping noise

[john cave]

Hi all,
1st time post i have a ford thunderbird 4 door auto with a 429 engine my problem is i get a tapping noise like a lifter but it's not the lifter
only get it when i place the car in gear and drive. Would it be the timing it has been changed to run on unleaded fuel the stainless steal valves have been
done to the engine thanks in advance

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[74 Harley]

Probably running a lower octane fuel, those engines run a little more compression than most of today's cars. Try the high octane fuel, maybe even octane booster. Good luck and keep us posted.

 

[DEVIL DOG 62]

open the hood and have it running and post a video of the tapping noise so we can diagnose it better

 

[john cave]

open the hood and have it running and post a video of the tapping noise so we can diagnose it better

Thanks mate it does not make the tapping noise on idle or reving the engine only when you put it in drive and accelerate ?

 

[DEVIL DOG 62]

Thanks mate it does not make the tapping noise on idle or reving the engine only when you put it in drive and accelerate ?

If you can jack up a rear tire put it in drive and see if someone can video the tapping noise while it's jacked up off the ground. Same as driving it just stationary

 

[74 Harley]

Don't forget to check the timing. It could be a little too far advanced.

 

[Frankie the Fink]

Low octane/timing pinging and lifter tapping are usually distinquishable.
You could run some octane booster through a tank full and see if the noise clears up.
Or a 50/50 mix of Av Gas and premium. 5 gallons or so shouldn't hurt your wallet...
If it really is pinging under load that can
be destructive so you need to address it.

If the pinging is under light load (curising) and the car has vacuum advance, you can do an
experiment by disconnecting and plugging it; if your pinging goes away the car has too much
advance timing and the whole curve should be examined.

The tapping may well be an exhaust manifold leak. A cheap mechanic's stethoscope

https://www.amazon.com/dp/B01BUJZBOO/?tag=thunderbirdforum-20

may tell the tale. If the noise decreases as the car warms up this is worth investigating.

If its a sticky hydraulic lifter a dose of Marvel Mystery Oil may well
clear it up (don't laugh its a real, highly regarded product).

https://www.amazon.com/dp/B0725JQXKS/?tag=thunderbirdforum-20

It may just be time for a valve adjustment BTW>

Finally if the engine is missing when the noise ( a "snapping" sound) occurs it could be a leaky spark plug wire or arcing
at the distrbutor cap; running the engine in the dark and careful observation can often reveral
arcing. Removing each plug wire individually while the engine is runnign should create about a 100 or more
RPM drop at idle, the cylinder that does NOT do this has an ignition problem.

BE CAREFUL DOING THIS CHECK!! Hot engine, high voltage, moving parts !