engine knock 88 240 non turbo

160k mi. Knocks loud at start up. You can here it destinctively from 30
feet away. Gets lower about twenty minutes at highway speed (55-60).
Is suttle but present at idle, after an hour of driving.
On start up with loud knock I can quiet it by pulling the number 2 plug
wire only. Should I be worried about throwing a rod.
I have been running thin oil in it for winter.
I read about the piston slap and do not think this is it.

 

It is not knock if it is at idle. You have a leaky exhaust manifold gasket.
The reason it is louder at startup is because the manifold has not expanded
to partially seal the leak. You should be able to see carbon deposits around
the leak. Replace all four exhaust gaskets.



Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca

void _-void-_ in the obvious place

 

Maybe, or maybe it's piston slap. Well known phenomenon in B230 engines.
Not familiar with it myseslf, but it's said to be worst when cold, and
diminishes as the engine warms up.

 

I agree, not rod knock because it quiets after the exhaust gets really hot.
In my experience, exhaust leaks are a fairly sharp tapping sound while bad
rod knocks are a deeper "thunk" sound. Mild rod knocks sound very much like
exhaust leaks, though. Piston slap is louder when the engine is cold, but it
quiets quickly. It also sounds deeper than an exhaust leak, more like a
clank.

My favorite technique for locating an exhaust leak:
Start with a cold engine. Connect the hose of a shop vac to the outlet side
of the vac, so it is blowing air. Empty the shop vac and run it for a few
minutes to clear grit out of the hose. Duct tape the hose to the exhaust
pipe of the car and start the shop vac. Feel around the exhaust with your
bare hand - even a small leak will be obvious.

Mike

 

I know for sure that the header pipe is leaking right at the manifold,
and it is a bad leak.
I need to replace two of the studs, and I am holding of until I do the
rear seal, which is also leaking. I have new motor mounts and was
going to yank the motor and tranny together to do all of this and some
other stuff. (correct timing belt,I think I'm off a tooth,fix leaky
water pump gasket,front tranny seals, rewire overdrive selonoid to
switch) I have a list.
Thanks
Ray

 

There ya go! Drive with confidence, but remember the exhaust at that point
has significant CO. Having had CO poisoning once, I can tell you it's bad
news. The sound you describe should be trivial enough, but if it gets louder
it may need attention earlier.

Mike