Which Radiator Cap Should I Use??? - Team Camaro Tech
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post #1 of 7 (permalink) Old Aug 10th, 07, 12:50 PM Thread Starter
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Which Radiator Cap Should I Use???

I have a 1967 Camaro with its original and completely stock 327 resting under the hood. Vintage air was professionally added which means the condensing coils now reside in front of the radiator. When I purchased the car it had a rotten radiator with a 7 pound cap on it and it would tend to run hot on warm days (20 to 25 degrees over the 165 degree thermostat). I flushed the system and replaced the radiator with a heavy duty 3 core and it still wants to run about the same temp. Will a heavier cap assist in cooling it down some?
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post #2 of 7 (permalink) Old Aug 10th, 07, 01:00 PM
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Re: Which Radiator Cap Should I Use???

With a new rad, use a higher pressure cap. 14-16 lbs is good.
The higher pressure raises the boiling point, but it won't make it run cooler.

What do you have for a ... Fan? Shroud? water pump? Thermostat?
Does it run hotter with the A/C on?
Does it run hotter idling in traffic, then cool down when you're up to speed?

I'd recommend:

Mr Gasket or Richardson hi flow thermostat, 180 is good.
New thermal clutch fan with 5 or 7 blade factory type fan.
Original type full shroud.
New aftermarket hi flow pump. I use a Wiand, and it cools really well. It's polished alluminum, but you could always paint it orange if that's your look of choise.





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post #3 of 7 (permalink) Old Aug 10th, 07, 01:02 PM
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Re: Which Radiator Cap Should I Use???

Also, factory A/C cars used a seal on top of the rad support to keep the air going thru the radiator rather than passing above it (these are reproduced) and a pair of "extenders" on each side of the rad support to prevent the air from going around that way and bypassing the radiator. (these are hard to find, but could be made fairly easily, maybe someone can make you a pattern?)

A front spoiler would also help at speed.





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post #4 of 7 (permalink) Old Aug 10th, 07, 01:04 PM
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Re: Which Radiator Cap Should I Use???

Is the radiator puking with the 7 lb cap when it gets warm?

165 stat + 25 degs = what are you worrying about? (190 degs) Heat makes power and 165 is just getting warm enough to get on it without fear of it being not warm enough. 180-200 is ideal...

I would recomend a 180 stat and a 15lb cap but it doesn't sound like you have any problems unless it is puking with the 7lb cap... More pressure will raise the boiling point which means the coolant temps can get hotter before blowing off any steam...

...Dennis

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post #5 of 7 (permalink) Old Aug 10th, 07, 02:35 PM Thread Starter
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Re: Which Radiator Cap Should I Use???

Thanks for the responses. The car has a flex fan, full shroud, high flow water pump and the new radiator was mounted using original brackets that prevent air from flowing past the radiator. The car does not overheat and spew water, but I have never been in traffic idling long enough to allow it to get that hot. I do have a billet overflow bottle and it seems to capture any water that may overflow. It does tend to run hotter with the air on. I will try the heavier cap and keep an eye on the temp.

Thanks again,

1967 Ragtop
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post #6 of 7 (permalink) Old Aug 10th, 07, 03:18 PM
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Re: Which Radiator Cap Should I Use???

Quote:
Originally Posted by DjD View Post
165 stat + 25 degs = what are you worrying about? (190 degs) Heat makes power and 165 is just getting warm enough to get on it without fear of it being not warm enough. 180-200 is ideal...
Somehow I missed that part. Agree with Dennis, you don't have a problem.





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post #7 of 7 (permalink) Old Aug 10th, 07, 04:12 PM
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Re: Which Radiator Cap Should I Use???

Here's what worked and didn't work for me:

My car used to run hot (meaning would get up to 220 degrees max) when idling in traffic for very long periods of time on 90 degree plus days. It didn't ever get above 190 when driving above 40 mph though. I tried various types of fans (clutch & flex) which didn't matter much when it came to idling for extended periods. Then I installed a Weiand aluminum high-flow pump which believe it or not actually made it slightly worse. Finally, I installed the biggest/most cfm electric puller fan available in place of the mechanical fan and now never goes above 185 no matter what the temp or how long it idles. It typically runs between 175 - 185 on the hiway. (all the above were with a Griffin Alum Radiator, 180 degree stat and 16lb. cap). Also - don't need to do a 50/50 mix for summer - use corrosion inhibitors with more water in the mix and will cool better. Lastly, the products that claim to lower temp 10, 20 or 30 degrees are bullcrap - tried several and never made a noticable difference so don't buy into their claims and save your money.
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