I am trying to determine if I have high head temps due to an intake leak and the resulting running lean.
I have read about spraying starting fluid or carb cleaner at the suspected leak.
Does one work better than the other?
So far I have tried starting fluid sprayed the bottom of the intake manifold.
The idle speed does increase but I am wondering if it is just getting sucked through the air cleaner.
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Michael- If you're spraying a short blast at close range it's being sucked through the intake leak and is telling you which manifold is the problem. Remember, even spraying either fluid through the air cleaner wouldn't change the fact that there's still an air leak and that side is running lean. Al
Try blocking the venturi stacks with your hand, one at a time. If the idle speeds up momentarily, it's an intake leak.
You can use WD40 also. It has propane in it.
DON'T USE WD-40!
It used to have Butane in it, but that was replaced by CO2 years ago.....but it also leaves a ****load of residue on whatever you spray it on that'll take forever and three days to dissipate Because it was formulated (after the 40'th try) as a water displacement medium.
Use either starting fluid or (my favorite) carb cleaner. Either will evaporate with no residue in about a minute.
short blasts (1 second or so) around whatever you're testing and move the nozzle between blasts.
BTW: I have banned WD-40 from my shop. There are LOTS better penetrating oils out there......PB Blaster, Liquid Wrench, Marvel Mystery Oil and my favorite, a 50/50 mix of Automatic Transmission Fluid and Acetone.
None of those are especially effective in finding intake leaks, though. 
If you really want to use WD-40 for something pretty effective, it clears up spark plug wires shorting across the cap when the cap gets wet (like on a dune buggy) Really well.
Gordon's right about the WD.
Another use for it (for those with fat whites or whitewalls) is that when sprayed on a rag, it's very useful for brightening/cleaning whitewalls.
That's good to know about the WD. Won't the carb cleaner eat all the paint off parts around where you spRay it though?
Frank: "Won't it eat up nearby paint?"
"It depends"
Carb cleaner somemtimes eats some of the Rustoleum paints, but when I've sprayed it on Krylon painted surfaces they seem to survive. It also seems to matter how long the paint has been on there - the longer the better to let it fully cure and "bake in" from the heat of the engine.
I guess it depends on what the part was originally painted with, and what you spray with. I honestly don't use starter fluid and haven't bought any in decades.
But my chair at work has not made squeak one in nearly two Months as a result of WD-40.
I am trying to determine if I have high head temps due to an intake leak and the resulting running lean.
I have read about spraying starting fluid or carb cleaner at the suspected leak.
Does one work better than the other?
So far I have tried starting fluid sprayed the bottom of the intake manifold.
The idle speed does increase but I am wondering if it is just getting sucked through the air cleaner.
High head temps highly unlikely caused by a leak in your manifold. With the motor off, reach into the fan and see if there is anything like paper that got sucked in. Also check your belt - too loose and the fan won't cool like it should. Needles to say that if your engine bay is not well sealed your fan will recirculate hot air and your head temps will got hotter and hotter.
All great points, Rusty; these are the first things to check when troubleshooting a temp problem. I remember Gene Berg saying that 1 tear in the engine compartment seal alone caused a 10' rise in oil temps in a bug of his.
