You will need to install then the right way round.
The gudgeon pin in the piston is off set to one side. This is to reduce the
amount of side thrust on the piston during the firing stroke.
The con rods have an oil hole that lines up with the drilling in the crank
pin in such a way that there is a squirt of oil on to the thrust side of the
bore as the piston comes down.
Another thing is that the crank pins in a 18G and 18GA are offset from the
centreline of the bore, the big end boss is offset on the con rods to
accomodate this. The rods for 1 and 3 have the boss offset to the rear of
the engine, the rods for 2 and 4 have it offset to the front.
You should be able to dismantle and reassemble these yourself with a bit of
care. The small end is held by a pinch bolt. Remove this completly and slide
the gudgeon out. Hold the gudgen by placing a bar through the centre rather
than clamping the con rod in a vice to avoid twisting the rod.
Are you sure that you have not swapped 1&2 and 3&4 as you assembled the
piston/rod sets into the block?
Cheers
ian F
----- Original Message -----
From: "Gordie's Garage" <mg_garage@comcast.net>
To: "mgs" <mgs@autox.team.net>
Sent: Sunday, May 16, 2004 12:33 AM
Subject: "front" of pistons
> I am assembling a 3 main 1800 engine and when I went to install the
pistons
> I discovered that the machine shop installed the rods in the pistons
> backwards. IOW, in order for the big end to line up with the crank
journal
> the "front" stamp has to be in the back of the engine.
> So, the question becomes, is the "front" stamp just to ensure that the
> pistons are installed in the correct orientation so that the rods align
with
> the crank, or is there some other reason that the piston is installed in
> that orientation?
> Would there be any harm in installing the piston "front" to the rear?
>
> The rods are the early type with the angled big end caps and a bolt
securing
> the wrist pin. Any reason why I can't change the orientation of the rods?
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