How high is up? there are too many factors to be able to answer that
question. The burn flame temperature in a typical engine is 3000-3500
degrees. That cools rapidly as the gas expands out the exhaust port
but that's where it starts. At the end of the exhaust pipe, even a
relatively short one, the temperature is only 200 degrees or
thereabouts. EGT is a relative indication.
That said, you probably have an air leak.
On Jun 30, 2008, at 9:17 AM, Barr, Scott wrote:
> Thanks, Bob.
>
> The probes in the header I was using at the last race weekend ARE too
> close to the head - about 3 inches from the port. So I didn't believe
> the 1400 degree reading on the EGT, as you suggest. We just installed
> the skinniest needles I own (BGs) and screwed the jets down until they
> were ready to fall out. With those changes, it was still running at
> 1400 degrees on the rear EGT at between 8,000 and 8,500 revs, with
> lower
> temps on the #1 probe. All four plugs had an even tan color to
> them, no
> white ones, no dark ones.
>
> Then the exhaust valve on #4, the cylinder with the higher readings,
> went away (stuck open, broke off?) and did some impressive damage to
> the
> piston and combustion chamber.
>
> Could be just coincidence that the highest EGT readings were from the
> cylinder where we had the problem with the exhaust valve, but I'm not
> inclined to bet another engine on it :-)
>
> This weekend we plugged in a spare motor and swapped to another header
> with the probe holes in the correct location, according to the
> instructions, and found that I still had significantly higher exhaust
> gas temperatures on #4 (1250 degrees at idle). I'm presently looking
> for an air leak to explain the significant difference between #1 and
> #4.
> If I don't find an air leak, I'll start looking for other
> explanations.
>
> But all of that raises the question - how hot is too hot? Is 1400
> degrees acceptable? 1450? All day?
>
> Scott
>
>
>
> -----Original Message-----
> From: rdavis4@cfl.rr.com [mailto:rdavis4@cfl.rr.com]
> Sent: Monday, June 30, 2008 10:57 AM
> To: Barr, Scott
> Cc: fot@autox.team.net
> Subject: Re: [Fot] EGT readings
>
> One of the dependencies to consider is the placement of the probe.
> If it
> is to close to the combustion fire then it will read higher than you
> think it should. You will have to conider ather factors in determining
> if 1400 is right or wrong, ie, spark plugs, holes burned in your
> pistons. I always considered 1200-1300 fairly normal. But again, probe
> placement is key.
>
> Bob
> GT6
> TR4
> Datsun 2000
> Datsun 510 trans am
> ---- "Barr wrote:
>> Here's a new topic - how hot is too hot, where exhaust gas
>> temperatures are concerned? My EGT readings a couple of weekends
>> back
>
>> were reaching 1400 degrees F. Is that considered too hot?
>>
>> Scott
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Bill Babcock
Babcock & Jenkins
Billb@bnj.com
503.936.7660
www.bnj.com
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