Ok, I have read every thread I can that is posted in (including the archives) on overheating - my issue is I have a 65 327/300hp with Factory A/C. When I bought the car, the former owner just put in a new B-Cool radiator. The car continues to run ok on the freeway (note that I am in Arizona so I am talking about 105+ days) at 180-190 Degrees - if I use the A/C maybe 5 degrees hotter. Once I exit and get into traffic and/or low speeds, it will climb fast and if I am not careful it will peg at 240 degrees quickly. I have a IR gun and shooting the t/stat housing backs up the guage. I have flushed the block 2 times, new water pump, 50/50 antifreeze, water wetter, GM NEW fan clutch, hoses, checked timing, vacuum over and over again. I just installed a modified 68 core support closed cell foam seal, sealed around the shroud to radiator, lower radiator, no front lic plate, etc, etc, etc. I know that there is a solution as my friends 67 427/400 with A/C will run 180 degrees in traffic! The only thing I have not done of course is step up and buy a new radiator - as many of your posts have said over and over again, check everything before you buy a new radiator - is it time for a DeWitt?? (No, Tom is not a relative!)???? Any other thoughts? During the winter here in AZ, it will get hot in traffic, but it takes longer. I really need to solve this problem....HELP! :cry

 

How does your spark advance map compare to OE spec?

Duke

 

The fact that it runs cool with plenty of air flow and hot at lower speeds makes me question the fan clutch. New fan clutches are set to lock up at a higher temp than the old ones, and there is always the possibility that even a new one just isn't working. The BeCool rad doesn't have the capacity of the DeWitts or the replacement that Tom sells.

Like Duke mentions, your advance curve could also be a problem, but if it checks out, take a close look at air flow. Sounds like you already have the seals in place. Do you have the correct fan? :steering:

 

Advance curve is fine......the fan clutch stops quickly after shutdown, but you could be right that it is not functioning correctly...but, the old one really was not bad and I did replace with no results....so, I will again double and triple check all the timing/advance issues and if still no luck, most likely will go for a radiator - the car is so original with exception of radiator and a few other minor issues I might as well put the correct date coded radiator in for the future. Thanks for the reply's!

 

What about the vacuum advance? Is it correct? What are the numbers on the bracket? Does it function to spec? Is it pulled to the stop at idle? Does the signal line show full manifold vacuum at idle? What is the idle vacuum? What is the total idle timing?

This is real basic stuff!

Duke


[Modified by SWCDuke, 10:04 PM 9/21/2003]

 

This statement is very true. None of the "replacement" rads have the same btu rating (not even mine) as the original. There is about a 10% reduction is cooling with the aluminum replacement (2row x 1" tube). This doesn't sound like a lot until you take 10% of 180 degrees. You multiply that by some factor because you have 105 degree ambient temperatures, and AC. I'm surprised it's not running even hotter than you stated.

I think what I would do is not only go with the factory radiator, but add the 16" fan as well. I have had great success with this package, even SB to BB conversions. Guys tell me they NEVER go over 180. The reason this works is because the plate type radiator is so 3" thick and the engine fan can only pull so much air through. The fan more than doubles the air flow and the radiator performance goes way up. I want to be careful in recommending this and state that not everyone "needs" an electric fan. Most people don't. It just that there is more cooling available if you feed it more air.




[Modified by Tom DeWitt, 3:34 PM 9/22/2003]

 

I would check timing & also - what about your thermostat? - may be sticking

 

Thanks for your assistance! I knew I could count on some very good advice - I will double check everything again this weekend and keep you posted. Yes, I do have the correct fan. I am going to have Joe Reno (Howard Goehring mechanic at Howard's Corvette's) assist me to make sure I have not missed something - then, if not, I will go a radiator. Tom, the additional fan idea looks good, but I assume it can be added later if the radiator still needs assistance?

 

Now I'm a little worried. I too have a problem with overheating in very hot weather. My SB will run around 180 or below in regular nor. cal. weather. But, when it's hot, like this past weekend, and I'm in stop and go traffic or climbing a grade on the freeway, the temp gauge will slowly climb toward 220. But, what's more of a worry, is that when the engine get's that hot, I'm blowing cooland through the overflow tank.

Sunday, I added two gallons of coolant to the radiator after I got home. That's a lot. I've replaced the caps, flushed the cooling system twice, checked the timing, and, in hot weather, still the same problem.

I've ordered a becool replacement radiator and will buy two new caps. I'll see if that works. I sure hope so. :confused:

 

Just a suggestion when you go to the mechanic. Have him run an exhaust gas test on the coolant. You can have a small crack in the head gasket and let a small amount of exhaust gas into the cooling system which will eventually super heat the coolant. At highway speeds the airflow overcomes this and you are ok, but in traffic there is not enough air flow to overcome. Sounds crazy, nope I have had this happen on 2 different cars, not vettes but principal still the same. Finally, as a double check is the vacuum advance hooked to manifold vs ported vacuum?

 

Hey Motro...save your money on the B-cool radiator purchase. Mine has only been in the car for just over a year and maybe 1,500 miles - looks brand new but it will not cool as good as others.....I am going to step up and buy the correct DeWitt.....he also has a cheaper version that is not date coded that is not that much more than the B-Cool....I have heard from enough mid year owners who have had similar issues who once they doubled checked everything else bought a DeWitt or Griffin and are very happy. If you really want a B-Cool....I have one! :thumbs:

 

Bigvette1 - thanks for the advice - we will check out the coolant......and vacuum advance :cheers:

 

[QUOTE]Get your ignition advance map back to design specfication.

Duke


QUOTE] :iagree:

JohnZ, did it again in this months issue of Corvette enthusiast. There is a great "step by step" article on this subject. Even I understood it.

 

How often are we replacing radiators to overcome other problems? From everything I have read, If I need to replace a radiator I will buy one from Tom. From posts I have read Tom would recommend making sure his radiator is not simply overcoming your problem.
Larry

 

Ron: Thanks for the advice. I think I've solved the problem. First, got the wrong b-cool radiator from Jegs so I sent it back. But, I did buy a larger 6 blade fan and took off the fan clutch. I'm running the 6 blade with no clutch in back of a big block, copper/brass, radiator. The car barely gets above 160 degrees, the thermostat opening temp. More tests today because it's supposed to be warmer. Keeping my fingers crossed.