C2 Cooling help.

[John S.]

Need some advice on my 67 300hp small block car. Added vintage air this past winter to help keep me cool in a black coupe in the desert! Finally getting hot here and am having some issues. Cruising at 55-60 mph car runs from 215-235 degrees on the gage. I have confirmed this with an IR temp gun at the water neck. A little hotter then I like for my 38k mile original motor! have searched all the posts and checked timing and vac advance as suggested. Everything good there. Also added the C2 a/c strip at the top of the radiator. My original thoughts were that the condensor is blocking air the radiator. BTW the radiator is original to the car! Here is to the point. When I put the temp gun on the inlet side of the radiator it reads 215. When I go to the outlet side it reads 190! That is at 95 ambient and idle. Fan clutch and fan are original to the non-a/c car. I am now leaning towards the fact that the radiator is 45 years old and just not able to keep up with the a/c now. Anybody checked inlet and outlet temps before and have the same readings? Thanks.

[Michael J.]

Re: C2 Cooling help.

I haven't checked inlet and outlet temps, but if you still have the original radiator, I would say the best thing to do would be to replace it with a DeWitts aluminum. Running at up to 235 when cruising at those speeds is too high. I have a new Dewitts on my '67 L71, and was cruising yesterday at 99 degrees at 65 mph and the temp was 185-190.

[John S.]

Re: C2 Cooling help.

Already talked to John over at Dewitt's this morning. He agrees. Also he explained that even low mile cars that have the original radiator end up with an insulating scale coating the inside of the entire radiator which greatly reduces the cooling capabilities. Felt the same way as you about the running temps especially for a low horse car.

[Duke W.]

Re: C2 Cooling help.

The high silicate "green" antifreeze that most of these cars have seen most of their life were good at preventing corrosion and subsequent leaks, but they laid out a lot of inorganic salts over the years that insulate the tubes and greatly reduce heat transfer.

There's no real test that I know of to determine if your OE aluminum radiator has arteriosclerosis (on a brass radiator you just unsolder the end tanks and inspect the tubes), but 45 years is a pretty good run. Hot running on level ground at highway speeds is usually an indication of radiator heat transfer degradation.

Use of a modern HOAT antifreeze like Zerex G-05 will significantly reduce the rate of deposit buildup, so with proper coolant change intervals the new radiator should last longer than 45 years.

If you have a '66-'67 300 HP/PG car with AIR there are other issues to discuss.

Duke

[Michael J.]

Re: C2 Cooling help.

Duke, as usual, is very correct about all that. Here is a picture of my original L71 radiator insides at 60,000 miles after all that wrong anti-freeze, needless to say, when I replaced it Zerex G-05 now keeps her cool. In this thread:
https://www.forums.ncrs.org/showthre...81638&uid=6183

[John S.]

Re: C2 Cooling help.

Thanks for the replies guys. Placing the order with Dewitts tomorrow after I take all the numbers off of the original one tonight. I will change to the newer coolant at the same time. Should I try and open up the block plugs to get all the old coolant out? Done this before on other engines and it is never easy. As to Duke's point about 300hp powerglides, my car is 300hp 3speed (1 of 180 something) radio delete no option coupe. If you've seen it before you would not forget it as it is black with teal interior, numbers matching Duntov car. Love driving the hell out of it, that's why I put the air in it!

[Michael J.]

Re: C2 Cooling help.

I just did a quick flush through the heater hose, too much trouble for the full deal I think. Also, the G-05 should be compatible with your existing anti-freeze. After my switch, the clear stuff was just a little discolored by the orange stuff I had. And that car sounds very unique, wonder who would have ordered such a stripped down car.

[Duke W.]

Re: C2 Cooling help.

The block plugs should always be removed when changing coolant, but since some have probably NEVER been removed, they may be seized.

Use a 6-point socket and a big breaker bar. Put a little torque on the bar, then jerk it. If they won't budge you can back flush the block through the heater hose nipple on the inlet manifold to get all the old coolant out.

If the plugs do come out, reinstall them with some pipe joint compound that you should find at any hardware store. It is designed to seal tapered thread water and steam fittings.

Only install the plugs "snug" - no more than about 10 lb-ft of torque. I don't think NPTs have torque specs other than tighten until there are no leaks, and with pipe joint compound they should not leak or loosen at 5-10 lb-ft torque.

Duke

[John S.]

Re: C2 Cooling help.

Michael,
Thought was always that it was a loss leader car for the corner of the lot run on special for $3,999. Problem is the color combo would not be one that Chevy would run on a no option car. Tank sticker is still on it and lists only "standard engine" and "standard trans". Like I said earlier, I love the color combo and I drive it as much as possible!

[Michael J.]

Re: C2 Cooling help.

Michael,
Thought was always that it was a loss leader car for the corner of the lot run on special for $3,999. Problem is the color combo would not be one that Chevy would run on a no option car. Tank sticker is still on it and lists only "standard engine" and "standard trans". Like I said earlier, I love the color combo and I drive it as much as possible!

True, that teal interior is not something a dealer would just check on a box with a black car. I suspect somebody had some definite tastes and filled the order out accordingly.

[Al R.]

Re: C2 Cooling help.

Hey Duke, elaborate on the 300Hp powerglide with A/C a little bit. I'm in the process of restoring mine, and now would be a good time to solve problems before they present themselves. Thanks! Al

[Gerard F.]

Re: C2 Cooling help.

John,

I've got the Vintage Air on my 67 (as you know), and was having some overheating problems. I thought about replacing the original radiator, but thought I'd try a reverse flush at a shop without removing the radiator, a new refurbed dated water pump, and a refill with Zerex G-05. Also a new fan clutch.

That worked, and I now cruise at 180-190 even in the hottest weather and with the Vintage Air blasting. Maybe worth a try before you replace an original part.

[Duke W.]

Re: C2 Cooling help.

Hey Duke, elaborate on the 300Hp powerglide with A/C a little bit. I'm in the process of restoring mine, and now would be a good time to solve problems before they present themselves. Thanks! Al

I said 300 HP/PG with AIR. This configuration, required for California in '66 and '67, had a very severely retarded spark advance map at low revs, and I recommend converting it to the conventional spark advance map as used on 49-state cars.

See the CSM and AMA specs for the differences.

Duke

[Randy S.]

Re: C2 Cooling help.

"Also added the C2 a/c strip at the top of the radiator. "


John,

66 and 67 AC cars also had a radiator fan shroud extension. I am sure a new radiator will be a big help but the shroud extension will likely boost the efficiency a bit.

Randy

[John S.]

Re: C2 Cooling help.

Any pics of the shroud extension. I did not know there was a difference!