losin my cool

[Mike M.]

I have a 64 300hp roadster that runs right at 180 degrees as long as I'm moving forward. Stop and go traffic sends my thermostat to 220 degrees fairly quickly. It will get right back to 180 degrees once I'm back up over 30-40 mph.
I've replaced and checked everything I can think of....new hoses, new water pump, new thermostst. I have the correct fan shroud, fan & clutch, I have a Ray temp gun and my temp gauge is correct. Heater core is fine, have new coolant, and the system including the block has been flushed. I finally gave up and bought a new DeWitt's radiator. Still have the problem! Also, the timing is correct, the engine runs strong and no apparant gasket problems.
I don't know whether or not the following would have any impacts, but the engine is a 67 corvette 300 hp block with 64 365 hp intake and exahust manifolds. It also has a mild cam (though I don't know the specs on it).
I sat next to a guy with a 61 vette last night on Woodward (gearing up for the Cruise) and he pulled over for the same reason as me. He runs fine until he get's in stop & go traffic. Are we the only two out there with this problem? Any suggestions would make me a very happy cruiser this weekend! thanks

[Gene B.]

Re: losin my cool

I would check your fan clutch. It probably is bad. The fan clutch is design to tighen when the temperature rises. A bad clutch will not spin effectively to pull enough air through the radiator.

That is why when you are moving the air is forced through the radiator, but when you stop, there is not enough air being pulled through the radiator.

Gene

[Robert Wingerter]

Re: losin my cool

**NOT politically correct answer ** but I had the same problem, did the same things (including new clutch fan). Just last week gave up and went to an electric fan kit from Dewitts. You can still use the factory fan shroud to keep a semi-original look. Solved the problem immediately.

[Robert Wingerter]

Re: losin my cool

** Forgot to add ** if you go this route, spend the extra for the curve blade, 16" kit. The straight blade kit is SO LOUD its embarrassing. I had to swap after 1 day. Couldn't deal with the noise.

[Chris C.]

Re: losin my cool

Just a reminder that if your fan clutch is a gm service replacement part (not original to car) it is actually designed for later models (C3) and has a higher temperature at which is engages. You can seach the archives for more information, but it was very simple to lift up on the coil spring on the front of the fan clutch and rotate it out of the middle of the two tabs, this effectively lowers the temperature at which the fan clutch engages, thus runs cooler at idle.

[Timothy B.]

Re: losin my cool

Mike,

If you have the original 300 HP distributor and vacuum advance, the low manifold vacuum of the mild cam will not be enough to pull the vacuum advance can to it's limit at idle. The result will be low idle timing and conditions just like what your experencing. Look in the archives for tons of discussion on this subject and I think you will find your solution. Also check your heat riser to make sure it's opening and closing without restriction.

[Gerard F.]

Re: losin my cool

Mike,

Have you checked the carb for vacuum leaks around the base gasket and throttle shafts. Maybe try running a little richer at idle.

Just a thought.

Jerry Fuccillo
#42179

[Mike M.]

Re: losin my cool

All excellent suggestions. thanks! It does run a little lean.
I have Pertronix ignition, new clutch fan, and heat riser is new as is the entire exhaust system. I'll check to see if those parts are still working and also re-adjust the fan clutch spring. Electric fan will be a last resort, but I'm glad to know it should work if I have to buy one.

[Mike M.]

Re: losin my cool

it is a Paragon replacement which says it's good for 1960-1970. The description states "does not look exactly like the original". So I'm guessing it's GM replacement. When you rotate the spring, are you tightening it or loosening it? thanks

[John M.]

Re: losin my cool

Hey Mike, Same name.
Does the cooling system spit out any coolant at 220? I think it's a 15 PSI system and should run at 210-220 without any problems as long as it's not losing coolant. There is no reason why it shouldn't run perfectly with all the cooling system stuff you have done unless the block is just plain clogged up or full of trapped air.

[Rob A.]

(Message Deleted by Poster)

Message Deleted by Poster

[Mike M.]

Re: losin my cool

It doesn't spit it out at 220. It will at about 240 (before I replaced the radiator, and I have not tried to push it that far yet). I think the cap is 16 lb. I don't mind running at 220, I have read that that's fairly normal. Maybe with the new radiator it won't go over 220. Guess I'll have to try it. thanks

[Tracy C.]

what if you take out the clutch and bolt the fan

(or a newfandangled flex fan) direct to the pump using a spacer? This should rule out a faulty fan clutch if it still gets hot.

tc

[Gerard F.]

Re: losin my cool

Mike

If the carb is newly installed, sometimes it takes a while for the gasket to take a set. Try retightening the mounting nuts. I had this same problem, and it just went away after I tightened the carb nuts.

Also check out that suggestion on the vacuum vs vacuum can. Maybe advance the initial timing a little.

Jerry Fuccillo
#42179

[Rob A.]

Re: losin my cool

Mike,

Although I'm sure you've already considered this...you could buy a fan clutch from Kragen or Pep Boys and install it. It's a fairly inexpensive and relatively quick way to see if that is where the problem is.