I second Alan's suggestion about the fuel pump (and the plug wires, though
typically they'll work for awhile until the the dist. terminals mangle the
core).
Could also be:
- some sort of vapor lock (I had similar problem out of Needles, CA at
115degF ambient with a heat-soaked engine, but it smoothed out after
a couple miles)
- a blockage in the exhaust system (though I don't know why temp would
make a difference)
bs
***************************************************************
Bob Spidell San Jose, CA bspidell@comcast.net
'67 Austin-Healey 3000 '56 Austin-Healey 100M
***************************************************************
Subject: Re: high rpm - misfire - followup
> PD -
>
> Are you using copper core wires or graphite suppressor core wires? If
> you are using graphite suppressor core wires, they will not work with
> the Lucas Distributor Cap. You must use copper (or other metal) core
> wires. This can cause all sorts of misfiring problems.
>
> Also, have you checked your fuel pump? Is it dirty or are your fuel
> lines dirty? if so, it may not be able to pump enough fuel after it's
> gotten hot and your engine is starved for fuel when you stomp on the
> gas. Do you have gunk in your fuel tank? If so the lead can get
> clogged and starve your car of fuel.
>
> Just some thoughts.
>
> Regards,
>
> Alan
>
> '53 BN1 '64 BJ8
>
>
>
>> Listers -
>> A few weeks ago I posted about my 66 BJ8 running rough
>> at high (3500+) rpm. I have followed the suggestions of this
>> illustrious and knowledgeable list and things are noticeably
>> better but the problem now is more specific.
>>
>> Here's what has transpired so far. What I thought originally was a
>> bad coil --- was in fact a coil failing. The replacement coil (high output
>> type) made a big difference.
>>
>> New parts
>> ========
>> coil
>> pertronix ignitor
>> ignition wires
>> distributor cap
>> plugs
>> damper oil at 20W and present
>> vacuum advance checks out OK
>> dynamic timing set
>> both HD8 carbs rebuilt
>>
>> With this configuration, when I first go out for a drive,
>> the BJ8 performs wonderfully. There is only the hint of
>> a stumble at about 4000+ rpm.
>>
>> But drive it for while, get it up to temperature and it stumbles
>> worse and worse until it almost seems to have a rev limiter at 3000 rpm.
>> You can slowly get the rpms up and cruise along fine but any sort of
>> moderate or hard accelleration (load) is cause for what sounds like half
>> the cylinders missing. Back off and it cruises just fine.
>>
>> Plugs 1, 2 and 3 are slightly rich looking compared to 4,5 and 6 but all
>> in all, pertty clean.
>>
>> Could I have a distributor problem that is accentuated by heat?
>> If so, any suggestions on a remedy?
>>
>> Any thoughts on other causes?
>>
>> I have swapped most of the components listed above with other parts
>> including a different pertronix ignitor. With exception of the old coil
>(which
>> really runs poorly all the time), nothing seems to change the condition
>> when hot.
>> Could I have a new coil that's bothered by temperature?
>>
>> TIA.
>> -pd-
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