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Discussion Starter #1
I’ve searched the forums here multiple times looking for some direction, have tried a few minor adjustments but not getting fantastic results so I thought I’d ask for thoughts. Here’s the setup:

1968 Camaro SS, 502 GM Crate motor, TH 400 Trans.
Aluminum short-style water pump, Power Steering but NO AC.
4-core stock(?) brass radiator, 23-inch. Flow tested this past spring. Transmission Rad in front. No separate oil cooler.
Flexlite Black Magic X-Treme S-Blade, 21” x 17” single puller fan, shroud covers 90% of radiator, pulling 3,300 CFM (supposedly).
Fan has electric thermostat reading from radiator fin probe, set to come on around 180 degrees (slightly above lowest setting).
Running about 20% glycol with H2O and 1 bottle of Water Wetter with a 160 degree thermostat.
Crank Pulley is underdriven (I think) at 6 3/8”.
Don’t know compression for sure but am guessing stock spec of 9.6:1; Don’t know timing.

Here’s what’s happening: When outside temps are over 80 degrees (as has been the case here in western PA most every day this summer), it seems to runs ok in the 175-190 degree range for about the first 20 minutes, assuming mostly 30-40mph suburban street driving with occasional traffic lights. After 20-25 minutes of run time, temp begins to creep up to the 195-200 range and seems to stick there (unless I get a stretch of road a mile or so where I can cruise at 35 mph - that helps). If I hit a light that is longer than 60 seconds, it creeps to over 200 and has a helluva time coming back down. In fact, after 25 minutes of drive time, I get real nervous at lights because I am watching the temp gauge slowly creep up to 205…210…215 all while looking for a place to get out of traffic. I generally chicken out once it hits 210 and pull off and let her cool down for 15 min. Then start all over again if I want to go further.:sad:

At highway speed (50mph +) for any more than 5 minutes with RPMs are in the 2,500 range, it obviously heats up to 200 much quicker. One 85 degree day last week I was driving for about 8 miles on the interstate at about 60 mph, 2,500 rpm, and the temp actually hovered around 200 the whole trip. Only time it dipped below that was when I took my foot off the gas. I can’t believe at that speed, the airflow would be insufficient to cool the system unless the electric is interfering with flow of air?

Here’s what I’m planning to do: 1) check timing, but not sure what would be optimal for a crate 502, 2) replace the underdrive crank pulley with a standard and 3) as a last resort go to an aluminum rad with dual electric fans.
Any thoughts or advice would be appreciated!
 

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Brian 210 for a BBC is actually normal. I would look into an aluminum 4 core radiator before I did anything. Airflow is the key here in my opinion. You want airflow through that radiator. A trans cooler on the front of the radiator will impede some airflow. Can you add another fan in front. Just some thoughts. Here is a sponsor on our site: http://www.entropyrad.com/
 

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Discussion Starter #3
Thanks - I'll consider that.
200 doesn't make me too nervous, but 210 does because one time this summer on the way to a car cruise after 50 min of driving at around 195-200, I got to the cruise area and slowed down to 5-10 MPH on the main drag to find parking. It went up to 215...220...230...shut down, boiled over!

It seems like when I heat up the engine, the fan/rad/pulley combo isn't doing enough to pull the temp back down, especially at idle. I just hate having to keep one eye on the temp gauge at all times!
 

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I would get rid of the underdrive pulley as well.
 

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1st off why a 160 thermostat... u are not running LPG as a fuel... thermost only limits min temp running and should have a GM 180 deg in.. make sure it is the correct GM thermostat.
But that is not your issue...
you should have enough air flow thru the radiator at over 25/30 mph to kee the engine cool no matter what the ambent temp is ....if u do not
There is not enough water incontact with enough air.
This can be caused by
1/ blocked or part bloked radiator cores....often get bloked because raditor is no re done like an oil pump is when a new engine is built or put in...and any bits of gasket silcone break off and bloke already partly blocked cores.
2/ Water pump impeller slips on slines inside the pump... very rare
3/Restricted free flow of air... there is a resent thread on electic fans and not allowing enough air thru and adding flaps to the shrouds that close at low speed/stop because fan sucks air thru the radiator but swing open when at speed... thread has great pics to.


If I hit a light that is longer than 60 seconds, it creeps to over 200 and has a helluva time coming back down. In fact, after 25 minutes of drive time
This is sorta normal... after driving highway for a while, come off stop at an interesection, there is still a lot of latent heat in the engine, and at idle water flow is low, not enough to get that heat out quick...the temps rise, increase rpms(water flow) and start to drop.
Now if u dont have enough water thru (blocked cores) or air this phenomia then becomes excessive.
Other causes...which note here, the stock cooling system was way over built .. for back in the day and for modern use to... do not underestimate its efficiency.. its better than any modern system... unless an engine is extemely way out on timing or mixtures it is so efficient it will not regist.
So to timing...ball park..
intial around 8 to 12 degs
idle 16 to 22 depending on compression and how wild the cam
intial +cent between 32 and 36 all in about 3000/3200 rpms.. start at the higher
intial+cent+VA dont exceed 40/42 degrees...
If retarded a little too much, and econmy and power drops way off if is will cause hot running... way over advanced will also cause it
Lean mixtures will also cause it, espec if timinf is in ball park... if overadanced not quiteas much

So i would check 1st
A HC/COx check on the raditor for blown head gasket.. done assume it is not...local workshops usually do this for free, like check battery loads, 5 mins
Check timing.. idle , cruise... WoT while at it
Check mixtures , idle cruise around the 15 AFR and WoT mid 11s to mid 12s
Swap out the thermostat for a genuine GM 180 unit... and check it in a jug water and thermometer it opens at correct temp AND fully opens.
timing idle, cruise, check idle cruise and WoT mixtures

This all assumes raditor pump are in good condition...
All of the above correct them move to the electric fan shroud flaps.
 

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As Steps & Donny suggests, timing, mixture and go for an overdrive pulley.

You might for a science project, block off the radiator support around the headlamps, and the top on bottom of support to valance preventing recirculatiing hot air through the radiator.
 

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Does your distributor have vaccum advance? Is it connected to manifold vaccum? This will aid cooling at low rpm.
 

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Had the same problem with my 468, hitting 230deg. I junked my 3 core radiator and
bought a Griffin 2 row with the inch and a quarter rows. It did much better but not
where it needed to be. I finally removed the water pump and inspected the blades.
I bought a pump which was supposed to be a reverse rotation off ebay, it was even
stamped with an R on the impeller. When I took it to Checker they told me it was a
standard rotation one. It was a freak thing, but they told me it happens. Now car runs
no higher than 210 with AC in 110deg Phx weather. Also got the right vac can, B-28
for the lumpy cam and set total timing at 36deg. Hope this helps
 

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Discussion Starter #10 (Edited)
Somebody recommended a 160 stat. So I got one, and when I went to install it...lo and behold, it already had a 160 in it!! Go figure. I'll get a 180, but obviously that's not going to solve the problem.

I'm doubtful it's the water pump...It's the aluminum one that came on the 502 crate assembly and it's not that old. I'll see if I can get it checked out, though.

It does have a vacuum advance but unfortunately I honestly can't remember whether it's connected to the manifold or the valve cover. I'll have to look when I get home from work and maybe post a photo.

Thanks all - I'll start with Steptoe's suggestions and work from there. I appreciate all the help, I know it's hard to diagnose a problem like this over a forum...
 

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"John Z" wrote an article, that is on this web site, stressing the importance of using vaccum advance connected to manifold vaccum, NOT ported vaccum. It is worth the effort to find and read.
 

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My 502 is about 100hp over stock, cools great with the 40 y/o partially clogged 3 row and fan clutch. My 1st suggestion is to get as much timing in the motor as you can. 2nd, consider another set of electric fans, preferrable an OE-type. Or, the factory fan/clutch/shroud - they really move air.

I ran a set of Windstar fans which cooled as good as the factory mechanical system, but I went back to the mech system just to keep things simple. I think alot of these aftermarket elec fan co's over-rate or use a different rating system to come up with the CFM ratings. The Windstar fans pull close to 4000 cfm I believe. Need to upgrade the wiring for the amp draw that thing creates.
 

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Discussion Starter #13
I talked to a guy at a show recently who said he swore by a clutch fan on his 396 Chevelle and had seen other guys do the same on their BB's and solve their problems. Rick's and a couple other sites sell stock replacement shrouds and clutch fans- I'm seriously considering trying this route...but I get the impression that the 502 is something of a different beast and I don't want to fumble around buying wrong parts.
 

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Timing is extremely important, so make sure you have enough initial. I run around 30* (initial + vac).

After than, just get the correct fan and shroud for a BBC of your year. Some folks like HD fan clutches, I use a standard-duty as it does the job and isnt as noisey.
 

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Discussion Starter #15
Here's a photo of the engine. I need a vacuum and timing 101, but the vacuum advance runs into the carb (which I guess also qualifies as the manifold(?).

If I'm going to try the clutch fan, I imagine I'll have to replace that underdriven crank pulley as well.
 

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I talked to a guy at a show recently who said he swore by a clutch fan on his 396 Chevelle and had seen other guys do the same on their BB's and solve their problems. Rick's and a couple other sites sell stock replacement shrouds and clutch fans- I'm seriously considering trying this route...but I get the impression that the 502 is something of a different beast and I don't want to fumble around buying wrong parts.
I run a stock fan (#772) with a fan clutch on my 396. No issues at all.
 

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Brian, your vaccum advance is connected to ported vaccum. Connect your hose to the vaccum port at the base of the carburator which is manifold vaccum. Your idle speed will increase slightly when you restart the engine. Good luck, Jack
 

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Go to Team Chevelle and read Scott Wheaton's posts on cooling issues. The same principles apply and numerous people have had success solving their problems by following his suggestions. Not surprisingly using GM components. For one, your electric fan's shroud is only pulling through 90% of radiator. And electric fans draw better through aluminum radiators with fewer rows than a Harrison 3 or 4 core. The 160 stat in some cases does help with reducing temps. Autozone T-stat part #'s are over there. Using GM or aftermarket components in the wrong manner will cause overheating. Usually it's due to poorly thought out non stock setups. Tuning aside, if you defy the principles of air and coolant flow efficiency, you will overheat. Nothing wrong with a properly installed GM system to keep your BB cool.
 

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