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d.janssens - 28 Dec 2004 20:14 GMT

dear people,
i have a 350 - 1972 in my truck with a rattling noise while under
acceleration.
if i put the truck in park or and rev the engine slowly to say 5000 rpm
there is no mishap, but if i put it in gear and use the go fast pedal the
engine sounds like i lost a bearing or two.
so i replaced all bearings ( checked clearences ) but with the same result,
ratling under full load.
in then used the pull the plugwire method to find out it was cilinder # 5
that made the noise, when i left that one disconnected there was no noise
under acceleration.
so i tore the engine apart and found out that the # 5 piston had a very
clean top for say half the piston on the sparkplug side while all others
where black as you normally see.
the block is 0.30 overbored ( TRW forged pistons) and there is no ridge or
any other wrong stuff in there other than the skirts of the piston seem a
little scratcy
i thought it could be the piston pin that would cause the noise, but why
doesn`t it make the same noise than if you rev the engine in park, and why
is this #5 piston free of carbon ?
i am at a loss, please steer me in the right direction.
Thank you in advance
Dennes

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Santa - 28 Dec 2004 23:00 GMT

> dear people,
> i have a 350 - 1972 in my truck with a rattling noise while under
[quoted text clipped - 10 lines]
> clean top for say half the piston on the sparkplug side while all others
> where black as you normally see.

WAter leaking at intake Gasket

> the block is 0.30 overbored ( TRW forged pistons) and there is no ridge or
> any other wrong stuff in there other than the skirts of the piston seem a
[quoted text clipped - 5 lines]
> Thank you in advance
> Dennes

u possible could have a CRACKED PISTON

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Whitelightning - 29 Dec 2004 03:10 GMT

> WAter leaking at intake Gasket

If water/coolant was finding its way into the cumbustion chamber the entire
piston would be clean.
The other problem with this senerio you presented is there is no water
passage adjacent to the
intake port for #5 cylinder on a 350 cid small block chevy, or any other
cylinder for that matter.
Water flows across the front of the manifold to the thermostate housing, the
rear head passages are blocked off by the manifold, no water passage..

> > the block is 0.30 overbored ( TRW forged pistons) and there is no ridge or
> > any other wrong stuff in there other than the skirts of the piston seem a
[quoted text clipped - 7 lines]
>
> u possible could have a CRACKED PISTON

Is the head clean and dirty in the same areas as the piston?
have you checked the wrist pin for play?
Have you checked to make sure the piston does not extend past the the deck
when at top dead center? That it is below the deck the prescribed dustance?
Have you checked the clearance between the piston and the cylinder?
Did you plasti-gauge the crank bearings?

Whitelightning

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Santa - 29 Dec 2004 04:07 GMT

>>WAter leaking at intake Gasket
>
[quoted text clipped - 6 lines]
> Water flows across the front of the manifold to the thermostate housing, the
> rear head passages are blocked off by the manifold, no water passage..

Been since The 70's since I worked on the 283/327/350

But it seems like I remember that Water Flows near #5 #6 #3 #4 But it
doesnot continue to the INTANK, The INTANK GASKET Blocks The Hole's
because there is no passage in the intake, I remember something weird
about the intake Gasket and WATER passage !!
And WATER is there Because The EXHAUST Runs UNDER the CARB to HEAT the
intake to turn The fuel to a GAS on Startup,,and to cool the Block next
to those piston holes The HEAT RISER DEFLECTS the EXHAUST back to the
pipes After The intank & The Exhaust Manifold HEATS UP.

Been a long Time since worked in my Dads Garage

>>>the block is 0.30 overbored ( TRW forged pistons) and there is no ridge
>
[quoted text clipped - 25 lines]
>
> Whitelightning

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