350 Heating Up at Stops

[cebra]

I have searched and tried about everything I could find. I have a 350 with some sort of cam, headers, Edelbrock intake, HEI ignition, Edelbrock carb. It is heating up from 190 moving to 210 and beyond depending on how long I sit at stoplights. It had a flex fan, I tossed that and installed a thermal clutch and 7 blade fan. I put a 170 degree thermostat in it, new rad hoses, heater hoses, heater core. The radiator is a 4 core and looks fairly new. I also reduced the timing down to 6 advanced and gave it a bit more fuel. It runs great (less it diesels a lot as the idle is high due to the cam) but I want to add AC and it is already running hot. Also, it keeps 200 at stoplights when I drop into neutral (rpm increases to 1,200 from around 600 in gear). Any other things to try?

[Kudzupatch]

Fan shroud?

Have you verified the temp gage is accurate?

[kwmech]

How big is the radiator

[wesmigletz]

If you have a big cam I would run mre initial advance and limit your total. Try bumping your initial time up, should let you back off the idle speed screw. The higher timing wont make you run hotter, it may actually help with your temps. Closing the idle speed screw will help with your dieseling.

Also make sure your timing is advancing with RPM

I run 12* initial, 38* total with my low compression 350 with comp 262xe cam. I ran 20* initial, 36 total in a 383 with a 282hr cam, with 9.8:1 compression and AFR heads. Both idle fine in gear and work with stock radiators.

[tdangle]

I second the fan shroud. I removed mine to repair it. Stopped it would get hot really quick. When I reinstalled it the gauge never moved while stopped.

[68 P.O.S.]

I agree with the suggestions so far. The fan shroud is a must for proper air flow over the rad, your initial timing definitely needs to be increased to at least 12 degrees, your temp gauge needs to be verified to be sure are you really are reaching those temps, and your vac advance need to be on manifold vac as it also helps with cooling at idle and low load. It sounds like your current fan, fan clutch, and radiator should be more than adequate for your engine. You said it has "some sort of cam", do you have any idea what's in it?

[cebra]

I have a fan shroud, forgot to mention that. I am unsure of the dimensions of the radiator but it completely fills the area available.

Not sure on cam..it definitely has a pretty mean lope, I have never had the engine apart that far. I should mention that I did head gaskets not long ago as well to try and cure the issue.

I had it running at 12 advanced but it got hot pretty quickly, this was before the new fan/clutch so maybe I need to take it back up. I have probably reset the timing 50 times over the last 6 months. I don't particularly like how high the idle speed is so it doesn't stall when dropped into gear anyways.

[cebra]

I trust the gauge, it is a Bosch mechanical gauge. I know the vehicle is heating up in general as the air through the vents gets hot and hotter. Will make sure the vac advance is working, never checked before.

[Steeveedee]

The original setup was ported vacuum, and it didn't overheat at idle when new. I'm not going to chase that argument rabbit around, just pointing out a fact. In general, when a vehicle gets hot at idle and not when moving, it is air flow through the radiator. That is all that is different at low speeds, like say, 35 MPH. Of course once the engine starts to work harder at higher speeds, that can change. How hot is the coolant when you are driving on the road, and how long does it take to cool off once you are rolling?

After re-reading your OP, I'm going to say that the difference in idle speeds in and out of gear is also going to contribute. Not all, of course, since it just doesn't get as hot in neutral.

As a temporary measure, as hes been mentioned, advance the timing so that you can reduce the idle speed. You're working the converter at that high an idle, and that will heat the trans and the engine. You may have to go to a higher stall speed converter to completely address the issue. It's obvious that the convertor isn't all of the problem, since it doesn't cool all the way down when you put it in neutral.

[cebra]

At speed, any speed/rpm range/stepping on it, etc, it runs at 190. It only heats up when stopped. It cools back down pretty quickly once I get moving again. It will drop from 210 to 200 if I drop it into neutral but never clear back down to 190 at a stop. Interesting it cruises always at 190 when my thermostat is a 170 (lowest available). Since I don't live in a cold area, would it help to just pull the t-stat? It has been really hot here lately but this issue is only going to get worse with AC even though I plan to run a trinary and an electric pusher fan on the condenser (doubt that will help the overheating).

[tutone]

Hard to chase down sometimes. You dont need a high volume water pump pushing coolant through too fast. Not saying you have one, but its worth looking into. Timing is important and sometimes an electric pusher fan is a must. I have a zz430 in my 34 Ford and without the extra fan, it aint happening.

[Stocker]

Even though the radiator looks good from the outside, there could be trouble such as blockages inside.Check the front surface of it with an IR thermometer, looking for hot spots or cooler areas. Assuming it's a crossflow..... temps should be higher on the inlet side and get cooler as you go toward the outlet side.

[outfield]

you are saying that "the radiator looks fairly new". Have you had it flow tested? This is the one piece you have not done anything with.

[68 P.O.S.]

Good deal on the shroud, that has a huge effect on cooling. Are you sure the rad is good to go? A 4 row should be plenty. Could be clogged just enough to reduce it's efficiency maybe. The rad is the main part of your cooling system, do you know anything about yours?

Bump your timing back up to 12 or 14 and readjust your idle. If you trust your temp gauge that's good enough for me. You can get an IR thermometer to double check it.

Yes, check your vac advance. Make sure the weights move freely & are lubed and make sure the vac can diaphragm isn't leaking or blown out. Easy check...hook it up to manifold vacuum and the idle will jump noticeably. If it doesn't, the vac can is bad or you already had it hooked up to manifold.

[68 P.O.S.]

Originally Posted by Steeveedee

The original setup was ported vacuum, and it didn't overheat at idle when new. I'm not going to chase that argument rabbit around, just pointing out a fact. In general, when a vehicle gets hot at idle and not when moving, it is air flow through the radiator. That is all that is different at low speeds, like say, 35 MPH. Of course once the engine starts to work harder at higher speeds, that can change. How hot is the coolant when you are driving on the road, and how long does it take to cool off once you are rolling?

After re-reading your OP, I'm going to say that the difference in idle speeds in and out of gear is also going to contribute. Not all, of course, since it just doesn't get as hot in neutral.

As a temporary measure, as hes been mentioned, advance the timing so that you can reduce the idle speed. You're working the converter at that high an idle, and that will heat the trans and the engine. You may have to go to a higher stall speed converter to completely address the issue. It's obvious that the convertor isn't all of the problem, since it doesn't cool all the way down when you put it in neutral.

I hear you Steeveedee, but it doesn't matter what the "original setup" was because it’s no longer relevant (unless you’re doing a 100 point factory restoration). That's like suggesting not to advance the timing, or not to change the exhaust, intake manifold, carb, cam, etc. for better performance because that's not what the "original setup" was. If you want your engine to perform more efficiently, give more power, etc., you change stuff out and tweek settings to get it how you want it.

I do agree with you about the torque converter. Still, sounds like the rad to me tho.

[rpmerf]

I am going to lean toward a bad water pump, partially clogged radiator, or bad fan clutch.

I think it is concerning that your t stat is 170 yet you are running at 190+. It means your system isn't keeping up enough for the thermostat to close.

Where is the sender for your gauge? The stock sender in the side of the head can be effected by heat from headers. Mine read lower with the factory manifolds and heat shields. Intake should be more accurate.

Are you sure you system is well bled? Have an overflow? Consistent level?

[don t. - 72gmc]

Originally Posted by cebra

The radiator is a 4 core and looks fairly new.

Almost like we're talking about my 68 Firebird.
My rad looked fairly new as well, was the last thing I replaced.
Guess what fixed my issue.

HTH....don t.

[jabborabbo]

A completely different possibility - I had an exhaust manifold leak apparently for some time - I didn’t notice it until the bottom of the gasket at the #3 and #4 exhaust ports had blown away/disintegrated/whatever and a quite audible knock developed when I would first crank the truck. During the time I had the manifold leak, the temp idiot light would come on sometimes when I stopped after the engine was at operating temperature...that hasn’t happened even once this summer since I replaced the manifold gasket.

[Mike C]

I read a lot about mid-year big block Corvettes and cooling. The reality is MORE advance makes an engine run cooler.

Corvettes run hot. High compression, big cam big blocks run hot. You can mitigate that by getting your initial and mechanical advance curve to where it is the appropriate max advance for you and then you hook up the vacuum to MANIFOLD source which gives you tons more advance at idle which should help keep temp down as well as make for a smoother idle.

This is just ONE aspect of a car running hot and making sure a lot of the other hard components are in good shape as suggested above is mandatory as well.

[Coley]

...is your original dash still intact (w/ deluxe gauges) including the original temp gauge?
What does it read when hooked to the same sensor?

Do you (or a buddy) have a 'heat gun' (infrared)....pretty common these days for household stuff.
What does it say?....always a good idea to get a second opinion....always.

Coley

[mike16]

maybe a clogged radiator or a radiator for a six rather than a bbc v8.

If you look at the cooling specs there is only about a quart or so difference between a six and a bbc v8. but there is a huge difference between the six radiator and the 8.

nother thing is gas milage. if your driving habits are usual but your burning up alot of gas then that gas is not doing any work but it is taxing the cooling system. make sure your carb adjustments are not compensating for a Poor cam choice.vacuum leaks?

[Stocker]

May not be likely, but it's possible your new thermal fan clutch isn't working properly. Did you get a heavy duty unit? Probably need one, considering your modded engine. My factory A/C requires a HD clutch.

Differences in standard duty, heavy duty, and extreme duty fan clutches are explained here: https://www.haydenauto.com/featured%...s/content.aspx

Also, the fan should be roughly half-in and half-out of the shroud. If not, air can be pulled around the fan instead of through the radiator.

[dagnabbitt]

It wouldn't hurt - or be expensive - to do a flush. Did the truck sit for a while when you bought it/owned it?

Also, if you never set it up yourself, maybe check to see if the last guy put the fan on backwards, you never know...

[toolboxchev]

I may have to do that again just 4 month after doing the last one. You would be surprised at the amount of rust in the radiator fluid once drained. It looks nothing like what you see when looking at what is in the radiator cap.

[custom10nut]

Do you have a clutch fan? I was having the same issue as yours, and then replaced the clutch type with a 6 blade non clutch type. I haven’t had an issue since.
Seems to me that my old clutch was worn out, and wouldn’t tighten when it was supposed to.