FWIW, to backup what Dave has suggested I have noticed a real trend toward
resetting timing at high revs rather that the customary idle speeds.
Several sources are now suggesting setting timing on some of our LBCs in the
area of 32 to 34 btc at 3400 rpm. I'm a bit hesitant to hear my babies
scream that high (on purpose) but if it gets the cars running at their peak
performance then I guess I could wear ear plugs for a quickie adjustment.
Mark
----- Original Message -----
From: "Dave & M" <rusd@velocitus.net>
To: "Michael Salter" <msalter@precisionsportscar.com>
Cc: "HealeyList" <healeys@autox.team.net>
Sent: Tuesday, January 09, 2007 3:23 PM
Subject: Re: Pistons damaged again
> Hi Folks,
>
> I tell this to everyone who will listen, but few apparently do.
>
> On high compression engines, it is important to set ignition timing at
> an rpm where maximum static plus centrifugal advance (vacuum advance
> not connected) is all of the way in. Depending on the particular
> distributor, this could be anywhere from 4,000 to 5,000 rpm. Most
> engines will tolerate between 32 & 36 degrees of total maximum
> advance, depending on engine tune, fuel grade, & altitude. In other
> words, set for maximum advance & let the idle advance fall where it may.
>
> It seems that many folks still insist on setting advance at idle &
> letting the maximum advance fall where it may. This method is not
> precise. The distributor's initial centrifugal advance curve is very
> steep (advances quickly) at low rpm. Only a small error in the rpm
> that the advance is set at can make a very large error in the total
> advance at high rpm.
>
> Seat of the pants timing is never reliable. A few degrees of over
> advance "may" give better throttle response & a bit more overall
> power, But the risks are great.
>
> ------------------
> Quote Michael Salter:
> Detonation can be quite serious at highway speeds but completely inaudible
> to the driver. You can buy knock sensors which will turn on a light when
> detonation is occurring; might be a good investment.
> ------------------
> Quote Bob Spidell:
> "I'm not convinced that the fuels that are available today,
> particularly in
> CA I understand, are good enough to handle the amount of advance that the
> original distributors can produce. "
> -----------------
>
> I agree completely with Michael & Bob.
>
> Regards,
> Dave Russell
> BN2
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