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Re: Weird Question - Buffing, Sanding SU Pistons?

To: MG List <mgs@autox.team.net>
Subject: Re: Weird Question - Buffing, Sanding SU Pistons?
From: Max Heim <mvheim@attbi.com>
Date: Mon, 23 Jun 2003 12:58:59 -0700
Oops. This is a problem. You are correct in surmising that burrs and
scratches are not acceptable. However, significant removal of material by
sanding is also not acceptable in this application. In operation, the piston
is raised by aerodynamic forces. The clearance between the piston and the
chamber wall is carefully calibrated to achieve this effect.

Buffing out scratches has the effect of randomly varying this clearance
around the circumference and along the length of piston travel. This is not
a good thing.

Within reasonable limits it may not have a significantly detrimental effect.
But I can relate my own experience, where I had one particular burr in the
front piston which I had to smooth out. Since then, I have never been able
to perfectly sync the carbs, and the front one has a tendency to stick
slightly on overrun. YMMV, but I thought I should warn you before you went
to town on it.

on 6/23/03 12:30 PM, S Twigg at seanan@crosslink.net wrote:

> Everyone,
> I picked up a set of HS4s to convert my 75 B from the ZS that is
> currently installed.  When I was disassembling the SUs, the pistons were
> scratched by some grit or sand that was, unknown to me, in the chamber.
> I'm not sure if the resulting burrs will effect their overall operation
> but I figured it would be a good idea to somehow get rid of them.  Does
> anyone have a suggestion as to how I could remove the burrs/scratches to
> ensure that the piston rises and falls properly?
> 
> 
> Thanks,
> Sean Twigg
> 75B


--

Max Heim
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the primer red one with chrome wires

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