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RE: Ottawa GOF TF mystery

To: MG Mailing List <mgs@autox.team.net>
Subject: RE: Ottawa GOF TF mystery
From: "John M. Trindle" <jtrindle@tsquare.com>
Date: Sun, 1 Sep 1996 08:42:44 -0400 (EDT)
On Sun, 1 Sep 1996 bleckstein@monmouth.com wrote:

> pedal followed by a slight increase to make the slight hill. What happens is 
>a 
> suuden loss of power and a chainy pinging noise. If you push in the clutch 
>and 
> let the rpms drop to idle, then release the clutch the car recovers with full 
> power. The engine never dies when this happens, and if you push on( without 
> letting the rpms drop), the pinging continues .
> 
> The latest theory is timing. Although the car starts well, and runs great, 
>the 
> theory is that I am near the edge of advance or retard, and the extra advance 
> with a hot engine at high rpm pushes the timing to the edge and I get pre 

This sounds likely, although I would suggest that perhaps you are also
leaning out the mixture during the "slight increase" and that's
aggravating the problem.  Check the damping fluid, and increase the
viscosity if necessary (we've had this thread before, but I like the
originial straight 20W oil for HIF4s, Marvel Mystery Oil for HS2s, and it
is all somewhat dependent on whether it is summer or winter).

It's also possible that the whole thing is set lean, and/or you have a
small air leak.  But it sounds like you have done enough work on the carbs
to find the leak.

> detonation. Another theory relates to the head replacement. This is that a 
>fine 
> ring was left on the bores of the head when it was machined. This fine ring 
> heats up on steady runs of 4000 rpms and glows, thereby detonating the gas 
> before the spark. Aparently the machine shop should have sanded the edge of 
>the 
> bores lightly after planing the head. 

I think you'd see the problem in more than one specific situation if that
was true.

John M. Trindle | jtrindle@tsquare.com | Tidewater Sports Car Club
'73 MGB DSP     | '69 Spitfire E Stock | '88 RX-7 C Stock
"Don't look back, they might be gaining on you."


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