The obvious first question is what grade gas are you using? I'd assume you
are using 92 octane but, if not, that's the first thing you need to do.
The second thing is to do a compression check. Anything higher than 165 psi
per cylinder, cranking with the throttle held open, and you will always have
a pinging problem. Modern 92 octane just won't handle a compression ratio
much higher than 9.25 to 1 (which is roughly what 165 psi indicates). If
your cranking compression is higher than that, the only way you'll eliminate
the pinging is to run racing fuel or an octane additive, or lower the
compression by fitting two head gaskets.
Lawrie
British Sportscar Center
----- Original Message -----
From: "Craig Wiper" <craigw@sonic.net>
To: "mg mailing list" <mgs@autox.team.net>
Sent: Friday, September 20, 2002 9:13 PM
Subject: MGB pinging...
> Hi. I've been off of the list for a couple of years now. I'm finally back
> on.
>
> I installed a rebuilt (Glenn Towery) engine in my B about a year and a
half
> ago. I have been having a pinging problem ever since.
>
> I have a California early '74 B which is supposed to have the timing
> adjusted to 11deg BTDC with vacuum off at 1500 rpm. I've actually got it
at
> 8 degrees to lessen the pinging which I've been experiencing. Any closer
to
> TDC and it's very hard to start and doesn't run as good.
>
> I bought brand new HIF4 carbs last year for a 'smog' check (couldn't
adjust
> the old ones to idle low enough). I put a 160 deg thermostat in it to keep
> the temp down to help the pinging.
>
> In the mornings now, it seems OK with the temp reading below the N. In the
> warm afternoons however, with the temp right at N, I still get lots of
> pinging; especially between 2500 and 3000 in 3rd, 4th and 5th gears.
>
> I adjusted the timing to both extremes and have never been able to get rid
> of the pinging. I swapped the HIF4's for a Weber downdraft and I couldn't
> even drive it out of the driveway because it was pinging badly. So I put
the
> HIF4's back on. I haven't done a compression check. Glenn told me it was a
> high compression engine though.
>
> I never had this problem with the old engine. It blew some rings and it
was
> cheaper for me to buy a rebuilt rather than have mine fixed locally.
>
> Has anyone had a similar experience? Any ideas would be welcome. Thank
you,
> and best regards,
>
> Craig Wiper
> Santa Rosa, CA
> craigw@sonic.net
> www.sonic.net/craigw
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