Overheating at Low Speeds - Team Camaro Tech
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post #1 of 35 (permalink) Old Jun 14th, 18, 12:42 PM Thread Starter
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Mark
 
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Overheating at Low Speeds

Iím having some problems keeping my 69 Camaro cool while it is idling in traffic, and hoping someone can give me some advice to resolve it. My car has a OE style 21 inch 3 core radiator and factory fan shroud. Radiator is about 10 years old. I like to keep the car looking original, so a few years ago I replaced the flex fan I was using with the factory clutch fan set-up. The car has an OE style Hayden 2705 std duty clutch and a factory 7 blade fan (3947772). My car does not have A/C.

I can monitor the coolant temp using the EFI system. The cooling system has a 180 degree thermostat that I replaced recently to little effect. The car stays around 180 while driving at highway speeds, but will gradually heat up while idling. Iíve seen it get as high as 210 when the outside temperature is 70-80 degrees. The fan seems to pull plenty of air through the radiator, so Iím at a bit of a loss to figure out what to do next. Any suggestions?

69 RS, Hugger orange/black, Deluxe interior, Sony AM/FM/XM/CD, PS & PB. 355, forged pistons, Eagle rods, balanced, Iron Eagles, 9.4:1 CR, .038 quench, XR270HR Cam, Z28 intake, FAST-EZ EFI 2.0, Thorley Tri-Ys, TCI 700R4, 2400 stall, 3.42 posi
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post #2 of 35 (permalink) Old Jun 14th, 18, 01:17 PM
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Re: Overheating at Low Speeds

Maybe look at your tune, Engine in good shape, idle mixture, timing...

Water pump, thermostat issue... Just throwing out ideas.

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post #3 of 35 (permalink) Old Jun 14th, 18, 04:03 PM
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Re: Overheating at Low Speeds

I would say use Autozone 15356 160 thermostat and HD Hayden clutch.

Be sure timing is ok. I had the same problem and thatís what cured it. Learned it from WHEATON on Chevelle site.

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Last edited by rp930; Jun 15th, 18 at 08:25 AM.
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post #4 of 35 (permalink) Old Jun 14th, 18, 04:07 PM
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Re: Overheating at Low Speeds

Factory thermostat was 195*. These cars ran around 200* all the time.
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post #5 of 35 (permalink) Old Jun 14th, 18, 04:51 PM
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Re: Overheating at Low Speeds

Quote:
Originally Posted by rp930 View Post
I would say use Autozone 15356 160 thermostat and HD Hatden clutch.

Be sure timing is ok. I had the same problem and thatís what cured it. Learned it from WHEATON on Chevelle site.
Quote:
Originally Posted by jkuro View Post
Factory thermostat was 195*. These cars ran around 200* all the time.
160* T-stat will not make it run any cooler.

Has it always done this or is this something new?

What is your idle RPM does increasing it affect the idle coolant temp?

16# cap? Is it puking any coolant?

and 210* at idle is really not anything to stress over.

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post #6 of 35 (permalink) Old Jun 14th, 18, 07:29 PM
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Re: Overheating at Low Speeds

If your distributor is connected to ported vacuum, you won't have enough advance at idle and slow speeds.

Make sure it's connected to manifold vacuum.
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post #7 of 35 (permalink) Old Jun 14th, 18, 11:23 PM
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Re: Overheating at Low Speeds

Quote:
Originally Posted by NashvilleCat View Post
If your distributor is connected to ported vacuum, you won't have enough advance at idle and slow speeds.

Make sure it's connected to manifold vacuum.
Incorrect.. Ported. Manifold vacuum is just a bandaid for other problems... Typically tune is lean if need manifold vacuum (extra timing) for the slow burn... ( of course there could be other issues also... remember when you crack the throttle wide open ( no vacuum) your timing is jumping all over with manifold vacuum.

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post #8 of 35 (permalink) Old Jun 15th, 18, 01:52 AM
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Re: Overheating at Low Speeds

Quote:
Originally Posted by partsguy57 View Post
Incorrect.. Ported. Manifold vacuum is just a bandaid for other problems... Typically tune is lean if need manifold vacuum (extra timing) for the slow burn... ( of course there could be other issues also... remember when you crack the throttle wide open ( no vacuum) your timing is jumping all over with manifold vacuum.
Read John Z's "Timing and Vacuum Advance 101"

Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.

https://www.camaros.net/forums/13-per...nce-101-a.html
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post #9 of 35 (permalink) Old Jun 15th, 18, 07:00 AM
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Re: Overheating at Low Speeds

Quote:
Originally Posted by NashvilleCat View Post
Read John Z's "Timing and Vacuum Advance 101"

Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.

https://www.camaros.net/forums/13-per...nce-101-a.html
Thanks for posting this article. Too bad more people don't understand the advantages of full manifold vacuum. Ported vacuum was a crutch implemented to meet EPA mandates that resulted in negative unintended consequences, one of which was higher idle temps.

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post #10 of 35 (permalink) Old Jun 15th, 18, 08:09 AM
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Re: Overheating at Low Speeds

Quote:
Originally Posted by ctcz28 View Post
Thanks for posting this article. Too bad more people don't understand the advantages of full manifold vacuum. Ported vacuum was a crutch implemented to meet EPA mandates that resulted in negative unintended consequences, one of which was higher idle temps.
One guys opinion... Ported vacuum is correct... My father is a retired professional mechanic and I worked in the shop a bunch growing up and was taught that by him. ( my back ground auto parts and machine shop owner) you will find plenty on ported vacuum online also and the reason for being correct. Manifold vacuum can have it place, but is not correct and is used to cover other issues... ( you mention higher idle temps, but you do know lean also creates heat and using manifold vacuum can be crutch to cover this.. Check your tune...) in this case 210 is not overly warm.....

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post #11 of 35 (permalink) Old Jun 15th, 18, 08:26 AM
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Re: Overheating at Low Speeds

67-69 Camaros never came with ported vacuum. Beth is correct, use manifold vacuum.
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post #12 of 35 (permalink) Old Jun 15th, 18, 08:27 AM
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Re: Overheating at Low Speeds

Gee. And I thought it was going to turn into a thermostat debate. Itís a vacuum debate instead.
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69 COPO clone, 461" BBC 11.25:1 Compression
840 Rec Heads (2.25/1.88) AED 850 HO carb
Orig Exhaust Manifolds
Straub (Clay Smith) cam, 288/300 .600/.569 109.
TH400, 3500 stall, 4.11 12 bolt posi
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post #13 of 35 (permalink) Old Jun 15th, 18, 08:46 AM
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Re: Overheating at Low Speeds

I have no vacuum advance at all. I have very quick throttle response no heating problem sitting in a garage or traffic for 15-20 minutes idling and I get 14 mpg with a 540 horse SB
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post #14 of 35 (permalink) Old Jun 15th, 18, 11:18 AM Thread Starter
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Re: Overheating at Low Speeds

Thanks for the suggestions everyone. Timing is set at 12 degrees initial, 34 degrees total at around 2800 RPM. Distributor is connected to manifold vacuum that adds around 10 degrees at full vacuum. Idle speed target is set at 870 RPM. My car has FAST-EZ EFI, and I haven't moved the idle AF ratio target from the default setting (I don't recall what it is). My car doesn't have gauges, so I didn't have a way to monitor the coolant temps until I upgraded to EFI a few years ago.

Couple questions - I've noticed there are a few gaps between the fan shroud and the radiator, especially where the shroud and radiator meet at the top of the radiator. Would it help to plug that gap? What would I use? Also, would installing a HD fan clutch help?

Thanks again. Hope everyone has a good weekend.

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post #15 of 35 (permalink) Old Jun 15th, 18, 11:52 AM
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Re: Overheating at Low Speeds

I didnít see if you answered

Does the temp drop of you increase rpm at idle?

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