hey El,Don't forget,this engine is a furnace.If the pump is too slow and the heat is generated too much,then at idle ,the water can't cool enough.This is evidenced by the fact that on a cooler day , no problem.You dig? Does it make sense now?Also don't forget that when looking in the expansion tank,there is very little flow at higher rpm's.I do think you're right that the airflow is also a factor so I'm gonna get a fan shroud so I can utilize all of the radiator surface instead of 65% .Viper fan huh,thats a thought.but remember that this is a show and sound car and a radical cammed engine.Do they make the viper fan in chrome?Are you saying that both the water pump and crank pulley are the same size?that means that it's a 1:1 ratio.If it works for u that is fantastic but for a furnace producing engine ,I think that,s the difference .NOW TO BULLETBROWN,you are absolutely right about March.This engine needs a faster flow due to basically the fact that it has been set up as a high rev engine though I dont run it that way so I guess I got what I bargained for,a mixed bag of problems to solve one at a time.Hey thanks for the imput guys.Ya made me think even more now.Love talking to everyone.Don't stop now.Everyone is a help.Give me more! Love ya all my friends.By the way,this is the blue and silvered striped ,chrom engined cobra at the Shell Valley display at carlisle this year

Oh--if its a blue/silver striped shell valley, then bulletbobbrown's answer is best--

Here's Ford's part number for a FE bottom single row pulley that's 6 1/2" in diameter: C8AE-6A312-B. You can often find them on FleaBay. Coupled with March's other pullies ( 5 1/2" water pump & alternator) you'll get a 12% overdrive.

I had the same issue until I ditched the underdrive pulleys. People are quick to point to airflow through the radiator. Given, that is important part of the equation. But the ability to cool depends on having an adequate amount of air pass over a sufficient amount of water. If the flow of either air or water is insufficient, then the coolant will not be cooled by the air enough to absorb and dissipate the heat generated by the motor. The underdrive pulleys, a street RPMs, don't flow enough water for the Cobra application.

Lew, you touch upon the airflow and how it works after it goes throw the front opening in a Cobra . I hope to hear from the people who knows about this , I read something a few years ago . Air turbulence in front of the radiator is a problem and I would like to hear from the people who have info on this.

OK Jerry,now that was funny.Making harsh judgements about my blue and silver cobra.Just kidding.It did make me laugh after a hard days work.UNDY.Thanks for the part number.I really appreciate it.Hey LEW,I think the same way you do and feel that either the combination or maybe just the increase in flow will do the trick.Wanna hear something really bad?I was on my way home from a car show,the heat generated my this engine was so much that it expandrd the hydrolic fluid , pushed the slave cylinder .pushed the clutch to disengage and had no clutch .Stood for three hours waiting for a rollback at night with my everloving wife by the interstate.Now she won't get in it till it's all fixed and proove it to her.Heck,the idea to get the cobra was hers in the first place.Got a great woman. How's that for a story that started this hole mess.Gotta get her back into this car regardless of the cost.See ya guys.JOHN

Well the reason I am posting here is I have some experience trying to cool a furnace of my own: An all-cast iron 427 (block AND heads) inside Hurricane's body (quite thick fiberglass) in the fiery hell of Houston TX, where the temps have been at or above 100 every single day I have been in the car in July.

I get that, same condition as I see in my car when I look into my tank, very little noticeable circulation, not what you would expect. So I swapped out the Ebrock water pump, made no difference.

Assuming your engine is fine, your radiator is sufficient (may not be) this is likely just a heat exchange issue. This is why on cool days, and down the highway you run cool. But on hot days, sitting idle, you run hot. The radiator/fan combo is not dissipating enough heat from the coolant as it passes through the radiator. It doesn't look like it would, but proper shrouding and more fan muscle makes a HUGE difference in cooling these big engines.

Now one thing to consider is that both of your pulleys are both 5.2" and stock pulleys like mine are 6.5", so your water pump is turning 20% slower at a comparable idle (I think I got that right.) That could be contributing.

Forget the pulleys. Remove thermostat, replace radiator if necessary, utilize pusher and sucker fans, make sure oil cooler working(helps even at idle), and shroud the heck out of it.

alkir,a 427 ford needs to run at 180 to run well.It'S PRETTY WELL KNOWN AMONG FORD LOVERS rUNNING TOO COOL AND REMOVING THERM IS A GOOD IDEA TO LOOK FOR OTHER RESTRICTIONS.mAYbe i SHOULD HAVE USE A 350 CHEVY YES?It"a an iron block with alum. heads at 607 hp.I/m pretty sure at this point it"s the pulley size problem.We"ll find out shortly

Hi guys,here is an update on the overheating . I replaced the water pump pulley with a Kirkham smaller one and the temp. is holding at 190 degrees.Increase the RPM and you can literally watch the temp go DOWN to 180.Now today I will add a shroud and see what effect it has.Outside temp. is 95 degrees.Happydays are here again. I'll let you know what the stainless steel shroud does.It should help beacuse without it I'm getting 0nly 73% of the radiator being used.Back atcha later.

I solved this problem with dual (puller) electrical fans from W.D. Kydd plus a good shroud and a manual control of these electrical fans which provides an airflow of about 37 mph during stop. And also a dual core aluminium radiator from Ce Cool (26 inches) and a coolant capacity of about 2.5 gallons. You can also add "water wetter" from "Red Line" but I do not need it.
And one more comment: there is nothing in front of my radiator, not even a "griddle" to reduce airflow.