That sound like a valve issue to me. Stuck/slow combined with a
mixture issue maybe caused by an intake manifold leak. Yeah, intake
leaks usually cause a spit back on the intake side like 100 Sixes
always get, but the excess mixture can detonate in the hot exhaust
pipe. DOes the car have headers?
Wilko
On Mar 13, 2011, at 9:47 AM, Rich Chrysler wrote:
> Gary,
>
> Either something way out of time...valve or ignition (but you say
> you've
> checked that) or maybe a tight valve not being allowed to fully close?
>
> Rich
>
> -----Original Message-----
> From: healeys-bounces at autox.team.net [mailto:healeys-bounces at
> autox.team.net
> ]
> On Behalf Of warthodson at aol.com
> Sent: Sunday, March 13, 2011 10:19 AM
> To: healeys at autox.team.net
> Subject: [Healeys] backfiring
>
> We have been trying to find the source of backfiring & eliminate it
> on a
> friend's BN7 (twin carb). Every time he shifts it back fires one
> time, very
> loud. It sounds like a rifle shot. I am not talking about the normal
> rumbling
> during deceleration. The car has recently been fully restored. The
> engine,
> distributor & carbs were professionally rebuilt. We have double
> checked the
> timing & carb adjustments. We cannot find any exhaust system leaks.
> If there
> are any they are very small. The tail pipes exit in front of the
> left rear
> wheel. The muffler has some damage, it was partially crushed when
> trying to
> unload the car from a trailer when it got hung up on the trailer bed
> to ramp
> angle. However, I could not see, feel or hear any exhaust leak in the
> muffler
> or pipes. I have read previous posts on this subject & they always
> seem to
> say
> that the cause is running lean or rich or exhaust leaks. I don't
> think we
> have
> any of these issues. Can you suggest any tests we could do to
> isolate the
> cause of the backfiring? Has anyone experienced this type of
> backfiring &
> eliminated it? How?
> Gary Hodson
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