GrandSportC3

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:

Smokehouse69

Sounds to me like unequal fuel distribution in your intake, and number 2 is running much richer than the other cylinders.

GrandSportC3

What could cause such uneven fuel distribution?? I use a single plane intake with a direct shot at the valves... My thought was that maybe the intake gasket came lose and is partly blocking the fuel delivery to that cylinder :confused: :confused: but I'm not sure..

shoptek

I am glad to hear the compression is fine :cheers: :cheers: :cheers:

LFZ

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

redvetracr

Your intake is not as effecient as it could be.
...redvetracr

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.

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°.


[Modified by Pete79L82, 11:40 AM 10/18/2003]

1979toy

Bad plug wire giving a weak spark to that cylinder?

GrandSportC3

You can actually feel that the pipe is colder when you get close with your hand.. The gauge is accurate for sure...

GrandSportC3

I don't know how the intake could be the problem :confused: :confused:

It's a spider style single plane intake with a direct shot at the valves...

GrandSportC3

We actually took readings in several different situations.. and cyl number 2 was always colder...

GrandSportC3

That's what other people said.. However - when checking the plub on #2 after a 420 mile drive today - the plug was colored brown.. the way it's supposed to be.. If the wire would be bad it would cause the cylinder to run too rich and the plug would be black...

GrandSportC3

Well - I checked the temp after driving the car a while.. and #2 was always colder by over 100 degrees...

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.

GrandSportC3

Well - I checked the temps after driving at higher rpm.. and #2 was always low... I would suspect the plug wire if the plug would black from running too rich from a spark that isn't strong enough.. However - the plug was just the right color...

I somehow suspect a fuel delivery problem to that cylinder... Maybe the runner on the intake is somehow partly clogged???

redvetracr

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

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.

Tyler Townsley

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

GrandSportC3

How is it done??