Engine.. Header temp mystery...
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Engine.. Header temp mystery...
Yesterday - I met with other forum members (Shoptek and Electron Blue'02) to have dinner. Marc (Shoptek) had a digital laser temperature gauge with him.. We were checking temps on several locations on our engines.. I checked on each header pipe... The pipes of 7 of the 8 cylinders read around 300 degrees and the last one (cylinder 2) read below 200..,. I was shocked and thought that I might have bad rings or valves that would cause low compression... Today I bought a pressure gauge to check the pressure on all cylinders.. and the pressure was just about the same on all cylinders...
The engine still runs as good as it always ran.. but I have no explanation on why the header pipe on cylinder 2 (front right cylinder) runs so much cooler... I checked my valve springs, spark plugs etc and nothing seem to give me a clue why one header pipe is a lot cooler than others...
Any ideas??? :confused: :confused:
The engine still runs as good as it always ran.. but I have no explanation on why the header pipe on cylinder 2 (front right cylinder) runs so much cooler... I checked my valve springs, spark plugs etc and nothing seem to give me a clue why one header pipe is a lot cooler than others...
Any ideas??? :confused: :confused:
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From: Semper ubi, sub ubi
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Re: Engine.. Header temp mystery... (GrandSportC3)
Sounds to me like unequal fuel distribution in your intake, and number 2 is running much richer than the other cylinders.
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St. Jude Donor '03, '06, '17
Re: Engine.. Header temp mystery... (Smokehouse69)
Sounds to me like unequal fuel distribution in your intake, and number 2 is running much richer than the other cylinders.
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From: Lake Norman NC
Re: Engine.. Header temp mystery... (GrandSportC3)
i wonder how accurate those laser temp things are....supposebly, pretty accurate. but that doesn't make since since you got good compression on all cylinders....touch with your hand next time and see if its cooler than the others. :jester
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From: Yazoo City MS
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Re: Engine.. Header temp mystery... (GrandSportC3)
I assume you took the readings at idle. Raise to 1500 rpm for a few minutes and retake - my guess is the readings converge. Raise to 2000 rpm - closer. As previously mentioned, probably an anomaly of the single plane at idle. Also, just for kicks, shoot them cold - make sure some surface phenom isn't affecting readings.
Drifting
Joined: Oct 2000
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From: Shawano WI
Re: Engine.. Header temp mystery... (GrandSportC3)
When we run an engine on the dyno we have EGT's for all 8 cylinders at the same time. It an idle there is always a big variation in temps from cylinder to cylinder regardless of what kind of manifold you have. EGT's only become meaningfull when the engine is under load and then you try to get all the cylinders to be within 100° of each other. Under a hard load at full throttle you like to see EGT's t be around 1200 - 1250°.
[Modified by Pete79L82, 11:40 AM 10/18/2003]
[Modified by Pete79L82, 11:40 AM 10/18/2003]
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Engine.. Header temp mystery... (Redshark6974)
i wonder how accurate those laser temp things are....supposebly, pretty accurate. but that doesn't make since since you got good compression on all cylinders....touch with your hand next time and see if its cooler than the others. :jester
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St. Jude Donor '03, '06, '17
Re: Engine.. Header temp mystery... (redvetracr)
Your intake is not as effecient as it could be.
...redvetracr
...redvetracr
It's a spider style single plane intake with a direct shot at the valves...
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St. Jude Donor '03, '06, '17
Re: Engine.. Header temp mystery... (guvnerwl)
I assume you took the readings at idle. Raise to 1500 rpm for a few minutes and retake - my guess is the readings converge. Raise to 2000 rpm - closer. As previously mentioned, probably an anomaly of the single plane at idle. Also, just for kicks, shoot them cold - make sure some surface phenom isn't affecting readings.
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Engine.. Header temp mystery... (1979toy)
Bad plug wire giving a weak spark to that cylinder?
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St. Jude Donor '03, '06, '17
Re: Engine.. Header temp mystery... (Pete79L82)
When we run an engine on the dyno we have EGT's for all 8 cylinders at the same time. It an idle there is always a big variation in temps from cylinder to cylinder regardless of what kind of manifold you have. EGT's only become meaningfull when the engine is under load and then you try to get all the cylinders to be within 100° of each other. Under a hard load at full throttle you like to see EGT's t be around 1200 - 1250°.
Thread Starter
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Engine.. Header temp mystery... (1979toy)
Chack the resistance on the plug wires. If the #2 wire has a lot more than the others it could be giving a weak spark at idle only.
I somehow suspect a fuel delivery problem to that cylinder... Maybe the runner on the intake is somehow partly clogged???
Race Director
Joined: Aug 1999
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From: WI
Re: Engine.. Header temp mystery... (GrandSportC3)
Have you ever seen an "epoxied intake" ?? I have one, the floor and the runners have been redone in epoxy and it still needed a little dam in #3 to raise the exhaust temp, mine are all within 100*. Checking your EGT anywhere except at WOT is a waste of time, and checking a plug anywhere except after a clean cut is another waste of time. ...redvetracr
Le Mans Master
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From: Canada
Re: Engine.. Header temp mystery... (redvetracr)
I epoxied my intake, same as yours Olivier. We used to do that in the 74 when I ran 1/4's with the Kawi 900 team in Mission B.C. if I remember right we used to epoxy near everything to prevent leaks caused by minor pits in the surface that a gasket just did not seal perfectly against.
Melting Slicks
Joined: May 2001
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From: Nichols Florida
Re: Engine.. Header temp mystery... (GrandSportC3)
Do a cyl leakdown test on cyl 2 and any other cyl. I have seen small cracks in a head do this yet still have good compression.
Tyler
Tyler
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St. Jude Donor '03, '06, '17
Re: Engine.. Header temp mystery... (gdh)
I epoxied my intake, same as yours Olivier. We used to do that in the 74 when I ran 1/4's with the Kawi 900 team in Mission B.C. if I remember right we used to epoxy near everything to prevent leaks caused by minor pits in the surface that a gasket just did not seal perfectly against.
