Re: Spittin' MGB
On Thu, 18 Aug 94 09:29:42 PDT Andy McLeanwrote about his Spitting MGB
> Having finally got my '78 MGB idleing and running reasonably
> well it still exhibits an annoying habit. It starts well but
> backfires quite violently when changing up through gears until
> the engine gets up to normal operating temperature. I know
> that the valve clearances/mixture/timing are all about right
> BUT the check valve and gulp valve are both non-functional.
> Could either be the cause of my waking up half the neigbourhood
> in the morning ? I could just about believe that the exhaust
> blow-back through the broken check valve could be what I'm
> hearing but why would it go away when the engine heats up ?
> Cheers,
> Andy (amc@berlioz.nsc.com)
If you're getting backfiring through the exhaust when you lift
your foot off of the accelerator at high RPMs, it could be an
intake manifold leak, which could also be your gulp valve.
The standard test is to spray something like carb cleaner or
WD-40 or whatever on all the possible leak sources and listen
to some change in engine speed or sound. A change means the
stuff you're spraying has found it's way into the engine.
I dunno why it would stop when the engine warms up unless some-
thing is expanding with heat. I've never had that experience.
My problems always just get worse with time, heat or whatever ;-)
-- Dave L.
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