ignition timing vs. engine temperature

[ducktapeguy]

Ok, this is a simple question which I thought I knew the answer to, but I think just confused myself by thinking about it too hard

How does ignition timing affect engine temperature? I know with advanced timing the engine runs hotter, spark plugs run hotter, but what about retarded timing? I thought retarding the timing would do just the opposite, i.e. make the engine run cooler due to incomplete combustion. But I've found some conflicting answers. Some sites say retarding the timing causes the spark plugs run cooler (which makes sense to me) but I've also read retarding too much also causes overheating issues.

So Is spark plug temperature always proportional to engine temperature, or is it possible to have a hotter running engine but a cooler spark plug? And does the engine run coolest at the right (optimum) timing? Thanks

 

[Mark W]

Spark plug heat range has nothng to do with engine operating temps.

Retarded timing makes for a hotter running engine. The fuel is burned less efficiently requiring more fuel for similar power levels. However this fuel IS burning and creating heat as it exits the engine.

It is not so much that advanced timing makes for a hotter spark plug, but that a hotter prak plug is more likely to cause pre-igntion than a colder on, so when the timing is advanced,a rig with hotter plugs is more prine to this problem.


Mark...

 

[ducktapeguy]

Spark plug heat range has nothng to do with engine operating temps.

It is not so much that advanced timing makes for a hotter spark plug, but that a hotter prak plug is more likely to cause pre-igntion than a colder on, so when the timing is advanced,a rig with hotter plugs is more prine to this problem.


Mark...

Thanks for the response. Are you saying the engine runs coolest at the optimum timing?

Also, I thought advancing the timing will cause a hotter spark plug (not heat range, but actual temperature) because the cylinder temperature itself gets hotter due to higher combustion temperatures and/or pre-ignition. I know a higher heat range (hotter) plug will cause this to happen sooner, but it the plug itself does not add heat to the engine to cause this increase.

I ran across this graph

http://www.procarcare.com/images/shar/encyclopedia/8852VG01.gif

which shows an increase in the actual plug temperature as timing is advanced, but doesn't show what happens as it is retarded.

And I also made a mistake in my earlier post, I meant to say that I thought retarding the timing would make the engine run cooler due to lower peak cylinder pressures, not incomplete combustion. It would seem to me that the engine itself would run cooler (as measured by the coolant temperature) as the timing is retarded, even though the EXHAUST from the engine might be actually hotter. Like you mentioned, it's still burning and creating heat, but as it's EXITING the engine, so it seems as if less heat would be going into the engine itself as opposed to the exhaust. Maybe it's just too late and i'm getting myself confused, but I think I'll just take your word for it.

 

[sloanstavern]

The warmest it gets is just above the left most Mark. I did a test and placed some cardboard in front of the radiator. That raised the temp closer to normal. It does have a new thermostat and fresh coolant. I wonder if my timing is off, it is set right on the bb

 

[1911]

Retarded timing makes for a hotter running engine. The fuel is burned less efficiently requiring more fuel for similar power levels. However this fuel IS burning and creating heat as it exits the engine.

Absolutely; retarded timing burns fuel in the exhaust to the point that it will turn headers cherry red in no time at all. Not a good idea!

If your engine is running well, it's probably not a timing issue.

Sloanstavern: on an F/2F engine, it's much more likely that either you are missing the rubber gasket on top of the thermostat, or missing the thermostat altogether.

 

[antFJ]

View attachment 1180222 The warmest it gets is just above the left most Mark. I did a test and placed some cardboard in front of the radiator. That raised the temp closer to normal. It does have a new thermostat and fresh coolant. I wonder if my timing is off, it is set right on the bb

Without a temp gauge with actual numbers on it you have no idea what temp your engine is. Be careful with the cardboard, you could overheat your engine and never even know.

 

[Landpimp]

You do need a better way to check the real temp, but my 82 runs right or tiny bit above the 1st(1/3rd) hash mar, which according to my real temp guage is 185-195. I think if you looked in the owners manual you would see a large range on the gauge that is "normal"

 

[tls3601]

chucabra is right on, the thermo in my brothers '76 was installed upside down and with NO upper rubber o-ring gasket. Big surprise it would barely move the engine temp gauge at all..................

 

[sloanstavern]

Thanks guys I will pull thermostat and confirm.
I have lots of temps with my infer red themometer oil pan peaks at 110f and heads at 125f
Cat peaks at 250f

 

[Landpimp]

shoot the radiator(across whole unit), upper & lower hoses and the T stat with the temp gun and the PS side of the block(not head)

 

[sloanstavern]

Just pulled the themostat and it had a bunched up rubber gasket on the top. I cleaned and put a thin coat of sealant on the housing top, then clamped her down.

Will let let it set then fire it up and see what I get.

 

[sloanstavern]

After 25 minute hard drive,
Head. 150f
Exhaust manifold 450
Oil pan 155
Red hoses 125
Cat 250-325 funny how the outflow end is hotter????

 

[65swb45]

After 25 minute hard drive,
Head. 150f
Exhaust manifold 450
Oil pan 155
Red hoses 125
Cat 250-325 funny how the outflow end is hotter????

..........and the guage?

 

[sloanstavern]

Never leave the left most tick mark ( right by the C). It does move from hard left to the C then stops

 

[65swb45]

If it's REALLY hard left, it may have shorted once. Look at the position of a new guage on one of those Ebay clusters.