1967 327, Temp spikes at idle - Team Camaro Tech
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post #1 of 13 (permalink) Old Jun 26th, 17, 06:26 PM Thread Starter
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1967 327, Temp spikes at idle

Ok, All.. here is yet another Temp problem!

I have a 67, 327, brand new 3 core aluminum radiator with electric fan. Temp runs beautiful (165-185) all day while on the road and at red lights. Even hot and humid days. But after its been up to temp for a bit, if I stop and let it idle for 5 min or so (longer than your normal red light) The temp all of sudden takes off to 220ish. The temperature will come back down, but very slowly with fan on and driving.

Mechanical temp sensor at water neck. New radiator hoses that dont collapse but get to hot to touch. Stock water pump. Does have AC condenser in front of radiator unfortunately. 16 inch electric fan with aluminum shroud made for it and radiator.

Any ideas on how to diagnose or where to start would greatly be appreciated by this rookie!

Thanks again! G
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post #2 of 13 (permalink) Old Jun 26th, 17, 07:17 PM
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Re: 1967 327, Temp spikes at idle

I would start at the weakest point the actual gauge and or sender. Test the ohms you are getting when it "runs away" if it is factory sender and gauge.
Confirm temp with a infrared handheld. Gauge and or sender may be having connection issues if the gauge is reading higher than the sender and more then the filler neck reads on the infrared.

Also worth checking the actual thermostat and cycle the water temperature on the stove top by using a candy thermometer.
If a 180 unit - Cycle from just under 180 degrees to 220 a couple times and see if the spring on the unit is not fully opening the second or third cycle by the time she reaches 200. If 190 unit start at just under 190.

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post #3 of 13 (permalink) Old Jun 26th, 17, 07:29 PM Thread Starter
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Re: 1967 327, Temp spikes at idle

Thanks for all the advice Brian! I will try those this weekend! Any idea on the ohms i should be looking?

Thanks again! G
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post #4 of 13 (permalink) Old Jun 26th, 17, 07:38 PM
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Re: 1967 327, Temp spikes at idle

Getting back to basics; IF the motor remains cool at higher RPM on the highway THEN we can assume the radiator is working properly.

IF it overheats idling, THEN the fan is not pulling enough air through the radiator we know works to cool the engine (ipso facto I rest my case). There can be other issues besides using an electric fans, such as no fan cowling, but basically you need more air flow.

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post #5 of 13 (permalink) Old Jun 26th, 17, 08:07 PM
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Re: 1967 327, Temp spikes at idle

Just a thought, are you running a vacuum advance and is it connected to ported or manifold vacuum? If connected to ported, that can be contributing to running hot at idle. Check out the article at the link below.

http://www.camaros.org/pdf/timing101.pdf

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post #6 of 13 (permalink) Old Jun 27th, 17, 02:16 AM
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Re: 1967 327, Temp spikes at idle

Quote:
Originally Posted by GY67Camaro View Post
Thanks for all the advice Brian! I will try those this weekend! Any idea on the ohms i should be looking?
Ballpark references as it also depends on the make of the sender unit installed in the block:
Water Temperature Factory Gauge values
220F = 101 ohms
210F = 104 ohms
200F = 118 ohms
190F = 133 ohms
180F = 152 ohms
170F = 172 ohms
160F = 194 ohms
150F = 225 ohms

There are a couple stickies about temp senders and gauges in the electrical forum to reference for details.

Full chart of senders here:
https://www.camaros.net/forums/1607532-post6.html


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post #7 of 13 (permalink) Old Jun 27th, 17, 10:07 PM Thread Starter
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Re: 1967 327, Temp spikes at idle

Thanks Larger Dave and CTCZ. I will look into air flow and timing. I was blown away by the amount of air the electric fan pulls when running some very basic test, but maybe its still not enough compared to driving down the road.. I wonder how accurate the cfm ratings are on these fans! lol

As far as timing goes, it has and MSD electronic ignition, I forget the degrees advanced right now.. but can take a look when home from work in the morning. Any ideas what is just too far ahead of top dead sensor before it starts creating too much heat?

I really do appreciate all the comments and learning!

Thanks again! G
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post #8 of 13 (permalink) Old Jun 28th, 17, 05:59 AM
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Re: 1967 327, Temp spikes at idle

Read through the thread listed below and pay particular attention to posting #42 in the thread by Dave Ray as pertains to VA.

https://www.camaros.net/forums/18-eng...le-help-3.html

Also, there are followup articles written by JohnZ to his Timing 101 article that can be found at this link:

JohnZ's Technical Articles

Pay particular attention to the portions of these articles that pertain to the VA on your distrbutor. Does your distributor have a VA and if so it's not locked out is it?

You didn't mention if this overheating problem just started after you made some change to your setup or has always been a problem. You mention a new radiator and fan, but don't specify if those are new to the car or were in the car when you purchased it. I assume there is no air trapped in your cooling system. Also, overheating while idling can be more a problem of timing being too retarded at idle instead of too advanced as described in the articles/posts referenced above.

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post #9 of 13 (permalink) Old Jun 28th, 17, 06:51 PM Thread Starter
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Re: 1967 327, Temp spikes at idle

Thanks CTCZ... I will read both of those!!

To answer your question (somewhat), it is a brand new 3 core aluminum radiator and 16 inch fan. Model and make eludes me while I am here at work. I made every attempt to get rid of all air. Is there a way to find out for sure?

One more bit of info that I discovered today. The mechanical temp gauge hits 180 ish then jumps to 210 instantly. No sudden steady increase. The needle jumps in less than a second. I wonder if the mechanical gauge is broken?? If so.. anyone know a way to check that?

I really do appreciate all the advice as I am just jumping into the Camaro/classic car world and loving it all!

Thanks again! G
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post #10 of 13 (permalink) Old Jun 28th, 17, 07:29 PM
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Re: 1967 327, Temp spikes at idle

Quote:
Originally Posted by GY67Camaro View Post
I made every attempt to get rid of all air. Is there a way to find out for sure?
The old farmers trick to burping air of the cooling system is to park on an incline nose up, bag of sand or something a couple inches tall under the front pass tire only so the radiator cap is the highest spot.
Once radiator is cool remove cap, then start her back up and run to temperature so the thermostat opens and closes a couple times. Each time it is open push pull the bumper up and down and bounce her up and down a couple times from the drivers corner. Looks stupid. Works great.

Brian
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post #11 of 13 (permalink) Old Jun 29th, 17, 04:35 AM
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Re: 1967 327, Temp spikes at idle

Toss on a spare gauge and sender or borrow them from a friend. Most have spare gauges hanging around. If your fan and shroud set-up operating efficiently that's fine, but a stock system with a clutch fan will have no problem cooling your engine. A radiator consists of a core with rows, hence a 2,3 or 4 row radiator.

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post #12 of 13 (permalink) Old Jun 29th, 17, 06:10 AM Thread Starter
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Re: 1967 327, Temp spikes at idle

Sounds good! I'll do what I can to remove the air, if there is still some trapped in the system.

Unfortunately, I dont know a lot of guys in the hobby/trade. So I am learning a lot here and dont think I know anyone I can borrow a gauge or sending unit from. I will certain explore that idea though!
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post #13 of 13 (permalink) Old Jun 29th, 17, 11:27 AM
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Re: 1967 327, Temp spikes at idle

$20 with sending unit

https://www.summitracing.com/parts/sww-122272/overview/
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