combustion cylinder temps
- Thread starter steve c
- Start date
To put it in basic terms the coolant flows along block & around cyls from front of block to rear, then up thru rear of head gasket & along cyl head to front & exits via T/ Stat.
So there is a temperature gradient in that circuit..... when doing race jet boats we tried to keep that gradient within a 30° C window, any more than that it created havoc with piston to bore and other problems in relation to shut down & restart. Cars once warmed up dont [ or should not ] experience the wild temp swings that boats do in those circumstance's. The bleeds at rear that GT40's etc seem to require are just that -steam or air bleeds. I think most GT 40's built with an engine install that has the front of the engine elevated slightly could possibly get away without the rear bleeds, but they are handy if the motor is in a race situation to get rid of steam pockets etc
So there is a temperature gradient in that circuit..... when doing race jet boats we tried to keep that gradient within a 30° C window, any more than that it created havoc with piston to bore and other problems in relation to shut down & restart. Cars once warmed up dont [ or should not ] experience the wild temp swings that boats do in those circumstance's. The bleeds at rear that GT40's etc seem to require are just that -steam or air bleeds. I think most GT 40's built with an engine install that has the front of the engine elevated slightly could possibly get away without the rear bleeds, but they are handy if the motor is in a race situation to get rid of steam pockets etc
Jac,
So with some water flowing up around 1 and 2,, 2 and 3 ect in the block to the heads and balance of water having to flow to rear of the block getting heated as it passes by all the cylinderss then finally to 7 and 8 is cyl temp of 7 and 8 hotter than 1 and 2 or does fact that majority of water that goes into rear of the heads and then all the way forward make 1 and 2 the hottest?
Steve
So with some water flowing up around 1 and 2,, 2 and 3 ect in the block to the heads and balance of water having to flow to rear of the block getting heated as it passes by all the cylinderss then finally to 7 and 8 is cyl temp of 7 and 8 hotter than 1 and 2 or does fact that majority of water that goes into rear of the heads and then all the way forward make 1 and 2 the hottest?
Steve
Steve, with those cylinder numbers you have spent tooo long on the dark side with Mr Chevrolet, #'s 1 & 2 are the fronts while 7 & 8 are rear over in that camp
Now over with the good guys #1 & 5 are fronts & 4 & 8 are rears....... Yes the two front cyls/bores do tend to run cooler & depending on whether you have early or late water pumps there is a flow bias difference from left to right banks [ The later 'mixing bowl' type pumps tend to to have less difference ], there are small openings in the block/heads/gasket that send water up from block to head in the area of the plug boss & ex valve and these are sometimes eliminated in alloy heads, just as some early cast heads had steam holes that no longer line up with later blocks etc.
From my experience most cooling related problems seem to occur in #'s 5 & 6 if things start to get marginal, conversations I have had in the past with guys that have had lots more exposure to this stuff than me tend to agree, Nascar guys were actually dropping the comp ratio & total ign timing in the #5 cyl since that allowed them to push the envelope a bit further on the other good cylinders. A lot of circle track stuff [ left turn only] also has the added factor of centrifugal force causing the RH cyl bank[1234] to get more coolant than the left [5678 ].
Erratic thermostats cause problems on road cars where they open suddenly during a high speed burst as in overtaking etc & the sudden influx of cold radiator water will literally 'shrink ' the cyl bore of #5 to the point of grabbing & partial seizure of the piston, more prevalent on cast factory pistons or later tight tolerance stuff.
Now over with the good guys #1 & 5 are fronts & 4 & 8 are rears....... Yes the two front cyls/bores do tend to run cooler & depending on whether you have early or late water pumps there is a flow bias difference from left to right banks [ The later 'mixing bowl' type pumps tend to to have less difference ], there are small openings in the block/heads/gasket that send water up from block to head in the area of the plug boss & ex valve and these are sometimes eliminated in alloy heads, just as some early cast heads had steam holes that no longer line up with later blocks etc.
From my experience most cooling related problems seem to occur in #'s 5 & 6 if things start to get marginal, conversations I have had in the past with guys that have had lots more exposure to this stuff than me tend to agree, Nascar guys were actually dropping the comp ratio & total ign timing in the #5 cyl since that allowed them to push the envelope a bit further on the other good cylinders. A lot of circle track stuff [ left turn only] also has the added factor of centrifugal force causing the RH cyl bank[1234] to get more coolant than the left [5678 ].
Erratic thermostats cause problems on road cars where they open suddenly during a high speed burst as in overtaking etc & the sudden influx of cold radiator water will literally 'shrink ' the cyl bore of #5 to the point of grabbing & partial seizure of the piston, more prevalent on cast factory pistons or later tight tolerance stuff.
Jac,
No "dark side" here (actually running a Shelby 427) just that my brain not working when I posted cyl #'s above.
Reason for my question is that I changed coolant recently and wanted to make sure I had purged all air out of the rear of heads as my engine sits level. I actually raised the front of the car and purged ect but, to make sure no air pockets I measured front vs rear cylinder areas with an IR meter and found the rears a little hotter than the fronts.
So reason for the question was to determin if this is a normal condition.
Still wondering if 4 and 8 are expeccted to be hotter than 1 and 5?
Steve
No "dark side" here (actually running a Shelby 427) just that my brain not working when I posted cyl #'s above.
Reason for my question is that I changed coolant recently and wanted to make sure I had purged all air out of the rear of heads as my engine sits level. I actually raised the front of the car and purged ect but, to make sure no air pockets I measured front vs rear cylinder areas with an IR meter and found the rears a little hotter than the fronts.
So reason for the question was to determin if this is a normal condition.
Still wondering if 4 and 8 are expeccted to be hotter than 1 and 5?
Steve
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