At 11:38 PM 12/1/98 -0800, Neil Cotty wrote:
>....
>.... Well here I am spinning along at 4000rpm in second when there's a
funny noise, like a rattle, and then a clonk, clonk, clonk, clonk in time
with the motor. .... it sounds like something is inside the cylinder
whacking around .... I took the carbs off to see .... nope. The dizzy
appears ok, .... tappet all there - fine. .... did a compression test. 1-4
156,154,128,153. Put a bit of oil in the third cylinder and wham up it goes
to 155.
>
>Whats happened? .... The engine appears to be quite difficult to turn over
by hand now. ....
>
>.... OK I was giving it 'a bit of a roost' (revving it), .... didn't go
over 4500 anyways.
Sorry to be the bearer of bad news, but it sounds like classic symptoms of
a broken piston. Been there, done that (more than once unfortunately).
Don't blame yourself, sometimes they just get tired and crack from fatigue.
Although improper tune can contribute to it. Running lean and with the
timing substantially out of spec can cause it to run hot and lead to early
demise of pistons, rings and valves.
Remove the head. You may be able to see some damage to the piston from the
top, but not always. Remove the oil pan. You may find a few bits of
broken piston shirt in the pan, but not always. Look up into the cylinder
from below. You may be able to spot some damage to the piston that way.
If it is a broken piston, at that point just two rod cap bolts and it comes
out the top.
A new piston and rings and a few gaskets get you back on the road. Careful
if there's a ridge at the top of the bore, should be removed with a ridge
reamer. And you should hone the bore a bit before installing the new
rings. Take it in stride and give your car what it needs. Sometimes life
sucks, but you'll feel better when it runs again.
Barney Gaylord
1958 MGA with an attitude
PS
And over the years, 2 dropped valves that punched out the piston, two other
broken pistons, and two broken crankshafts (one with other substantial
internal damage, and none of this happening during hard driving (except the
last broken piston).
BG
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