Don,t Guess Deal In Facts

[Grumpy]

Bad news today as I cranked up the 68 el Camino after only 6 days of sitting idle to hear a loud clanking/slapping at the back of the engine,
probably cylinder #8.
The oil level is OK and Camino ran great the last outing to Lowe's on Saturday at low RPMs.
Hopefully it is only a blown head gasket.
I fear that I will have to have an engine rebuild by our local, reliable mechanic.

don,t guess deal in facts,
do some logical testing,
and inspect the engine carefully

Until you locate the source of the noise your only guessing.
it might be something as simple,
as a busted rocker or valve spring ,
or the flex plate touching the lower converter /trans dirt shield,
a loose converter bolt.
be aware of exhaust leaks, loose motor mounts, and loose/worn, u-joints,
and improperly adjusted throw-out bearings, can also make unexpected noises.
do a compression test and pull both the valve covers ,
and look for the noise source before you assume anything!

I once bought a "BLOWN UP" 396 BBC engine dirt cheap for parts,
that the owner swore had a bad rod knock,
I got it home and found the only thing wrong with the engine was two burnt rocker balls

I once purchased a 454 BBC that smoked like a mosquito spray truck, the owner swore
"the rings were shot"
once inspected it proved to be a leaking trans modulator valve leaking trans fluid get sucked into the intake manifold through a vacuum line.

I once had a guy bring a car into the shop who swore he needed a new muncie trans, the only problem was he had a linkage rod on the shifter had come off.