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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