Keith:
Just for giggles run a compression check. It's possible you have valve
seating problems causing back pressure in the carbs.
This will also show up any valve guide seizing problems, so make sure
you do the compression check with the engine at normal operating
temperature. It's unusual, but possible that the bronze guides are
galled and the valves are sticking.
Kelvin Dodd
> -----Original Message-----
> From: owner-mgs@autox.team.net [mailto:owner-mgs@autox.team.net] On
Behalf
> Of Plant, Keith Contractor (NCTAMS Naples N35)
> Sent: Tuesday, July 05, 2005 10:35 AM
> To: MG List
> Cc: 'mgs@autox.team.net'
> Subject: Pow, pow pow pow....er
>
> I have added a crossflow head and two Weber Side 40D's. I love the
power
> I
> am gettin gout of the engine now, but I only enjoy it after lots of
> backfires and under the hood the carbs also seem to release pressure
(not
> really a backfire sound, more of a pssssst sound over and over around
> 2000-2800 RPM). A friend mechanic and I tuned the carbs according to
a
> few
> guides we found on the net. The timing on the vehicle is perfect. We
even
> took it to a local mechanic (mind you an Italian mechanic so no
> guarantees)
> and he said it looked fine. What would be causing these
> backfires/backpressures? The Webers are brand new (now about 500
miles on
> them). I'm running cleaner through the fuel system as well as high
octane
> gas (already tried lower!). No luck at all. Plugs are clean, almost
brand
> new.
>
> Just looking for a next logical step.
>
> V/R
> Keith
> '69 B Roadster
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