Put the correct size rad in there 
Does size matter?
Thread Starter
Instructor
Joined: Jan 2006
Posts: 109
Likes: 55
From: Wake Forest, North Carolina
Does size matter?
I have a 69 coupe w/ 350 and 4speed. I have been experiencing an overheating issue while in traffic. The car has an aftermarket 17" flex fan with no clutch, factory fan shroud, and an electric 12" pusher fan. The radiator looks like it has been replaced with a brass one with side tanks. It is only 18" wide x 16 high and seems to be the standard replacement for 350 MT cars. Is that radiator big enough? Has anyone successfully cooled their car with that type radiator? I see Dewitts has an Direct Fit aluminum one of that size and some larger ones. Do I need to invest in a new radiator?
Race Director
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Racer
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Rad sounds smaller than what was originally there, plus copper/brass rad has only about 70% the cooling power as the same size plate type corvette aluminum rad according to DeWitts.
Just went thru this- wound up putting a DeWitt's original repro of my blown aluminum vette rad in w/ a 16" Spal electric fan. So far it's keeping my 500 hp small block cool- never saw it run that cool with the old 350 and probably crapped up original rad and fan/shroud. I know the temp guage is working- just never seen it sit that low after it's been running a while !
Just went thru this- wound up putting a DeWitt's original repro of my blown aluminum vette rad in w/ a 16" Spal electric fan. So far it's keeping my 500 hp small block cool- never saw it run that cool with the old 350 and probably crapped up original rad and fan/shroud. I know the temp guage is working- just never seen it sit that low after it's been running a while !
Thread Starter
Instructor
Joined: Jan 2006
Posts: 109
Likes: 55
From: Wake Forest, North Carolina
Thanks for the replies, but just wanted to reiterate that the core of the radiator is 18w x 16h not including the tanks. It does seem to be the common replacement from Napa, Parts America, or chain auto parts stores for a 350 MT car.
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Le Mans Master
Joined: Jan 2006
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From: Butler Pa
That is the correct size for a mt 350 car w/o ac. I have the smae copper rad in my '69... and it's doing a great job of cooling a 502. If the rad is in good shape, your problem is somewhere else.
Le Mans Master
Joined: Jan 2006
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From: Butler Pa
Pro
Joined: Dec 2008
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From: Frisco TX
bashcraft has it right, my '69 4 speed non-air car came with the small radiator from the factory - you probably have the steel shroud as well.
here is the Dewitt's rad/fan combo replacement - its SP016
Good Luck, Ed
here is the Dewitt's rad/fan combo replacement - its SP016
Good Luck, Ed
Team Owner
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St. Jude Donor '13-'15, '17 thru '22
I'm sure I have bored a few folks with this along the way, but I have had overheating problems on both my Corvettes, and BOTH times it was, at least partially, that I didn't have a front spoiler installed. What you have there should work if you have the spoiler.
Now, you did say that you are having an "overheating issue in traffic". The downside of functional spoilers is that they don't function when the car is sitting still. It is perfectly normal for Corvettes that are well-behaved and running at 180-200 all day to have the coolant get somewhat hotter when in traffic or idling for long periods. If we are talking about the coolant temperature going up to 220 in traffic, it may not be mentally comforting, but this is normal. If you are seeing temps over 230, I would consider this a problem that needs to be addressed.
Now, you did say that you are having an "overheating issue in traffic". The downside of functional spoilers is that they don't function when the car is sitting still. It is perfectly normal for Corvettes that are well-behaved and running at 180-200 all day to have the coolant get somewhat hotter when in traffic or idling for long periods. If we are talking about the coolant temperature going up to 220 in traffic, it may not be mentally comforting, but this is normal. If you are seeing temps over 230, I would consider this a problem that needs to be addressed.
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Former Vendor
Joined: Jan 2000
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From: Brighton
http://http://www.dewitts.com/pages/whyaluminum.asp
The replacement radiator the OP is talking about has a btu rating of 3290 btu/min. The factory radiator was rated at 4600 btu/min and our replacement Direct Fit aluminum unit is 4100 btu/min. The copper unit might work on cooler days but when you put in under load, like a hot day, traffic, and even high speeds, that's when you go over that 3300 btu rating and the heat rises. Hundreds of people have already been through this, here are just a couple of the testimonials we have on our website. http://www.dewitts.com/pages/testimonials.asp?catID=1
Le Mans Master
Joined: Jan 2006
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From: Butler Pa
This misunderstanding and debate never seems to go away but I will try again to explain this. What people mean when they say the aluminum is better, they mean the aluminum radiators cool better. They are not saying aluminum is a better conductor of heat, it's not. So how is this possible? Well it's not an issue of material vs material but rather design vs design. Aluminum radiators use wider tubes which provides more tube-to-fin contact. They also use a lower fin height which results in more rows of tubes per a given size. These two items is why an equal size aluminum radiator will run 20-40 degrees cooler than the copper unit. Also a copper radiator isn't ALL copper. The radiator is held together with lead, and that is not a good conductor at all.
http://http://www.dewitts.com/pages/whyaluminum.asp
The replacement radiator the OP is talking about has a btu rating of 3290 btu/min. The factory radiator was rated at 4600 btu/min and our replacement Direct Fit aluminum unit is 4100 btu/min. The copper unit might work on cooler days but when you put in under load, like a hot day, traffic, and even high speeds, that's when you go over that 3300 btu rating and the heat rises. Hundreds of people have already been through this, here are just a couple of the testimonials we have on our website. http://www.dewitts.com/pages/testimonials.asp?catID=1
http://http://www.dewitts.com/pages/whyaluminum.asp
The replacement radiator the OP is talking about has a btu rating of 3290 btu/min. The factory radiator was rated at 4600 btu/min and our replacement Direct Fit aluminum unit is 4100 btu/min. The copper unit might work on cooler days but when you put in under load, like a hot day, traffic, and even high speeds, that's when you go over that 3300 btu rating and the heat rises. Hundreds of people have already been through this, here are just a couple of the testimonials we have on our website. http://www.dewitts.com/pages/testimonials.asp?catID=1
So, basically what you're saying is an aluminum radiator design has more tube surface area than a copper radiator, and that's the reason for the improved efficiency, correct?
What is the difference in tube surface areas when comparing copper rads and direct replacement aluminum rads?
Just thinking out loud here, but it seems to me that an aluminum rad would need about 30% more surface area just to be equal with a copper rad.
Former Vendor
Joined: Jan 2000
Posts: 5,593
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From: Brighton
So, basically what you're saying is an aluminum radiator design has more tube surface area than a copper radiator, and that's the reason for the improved efficiency, correct?
What is the difference in tube surface areas when comparing copper rads and direct replacement aluminum rads?
Just thinking out loud here, but it seems to me that an aluminum rad would need about 30% more surface area just to be equal with a copper rad.
What is the difference in tube surface areas when comparing copper rads and direct replacement aluminum rads?
Just thinking out loud here, but it seems to me that an aluminum rad would need about 30% more surface area just to be equal with a copper rad.
Le Mans Master
Joined: Jan 2006
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From: Butler Pa
Le Mans Master
Joined: Dec 2003
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From: Fremont CA
I also think that there is a good chance that all your foam radiator seals are probably missing including the one between the hood and the radiator support. There is also a baffle betwen the radiator support and the front cross memeber that is probably gone. Look at Dr Rebuilds site for all the parts that were installed at GM to keep airflow proper through your Vette.
Heel & Toe
Joined: Mar 2009
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From: Lawrenceville GA
I also think that there is a good chance that all your foam radiator seals are probably missing including the one between the hood and the radiator support. There is also a baffle betwen the radiator support and the front cross memeber that is probably gone. Look at Dr Rebuilds site for all the parts that were installed at GM to keep airflow proper through your Vette.
Jeff