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Old 09-08-2018, 10:41 AM   #26
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Re: 350 Heating Up at Stops

What does your coolant look like? Are you running plain water or coolant mix?
Even if it does not get cold where you live to worry about freezing you need coolant mix for the corrosion protection. If the water is brown or the coolant is not bright green, flush the system before you do anything else. Scale and sludge in the radiator and engine water jackets will rob you of cooling capacity.
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Old 09-08-2018, 05:37 PM   #27
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Re: 350 Heating Up at Stops

I agree with bumping the base timing up some. Then reduce idle speed and readjust carb. Use manifold vacuum for the dist too. This should help to reduce engine temp and actually make the truck more responsive as well and use less gas too. Reducing idle speed will lower the trans fluid temp thereby reducing the heat load on the radiator.
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Old 09-14-2018, 03:11 PM   #28
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Re: 350 Heating Up at Stops

Originally Posted by 68 P.O.S. View Post
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.
Perhaps on the radiator, it looks very new and clean and it never heats up besides when it is stopped. I may have to bite the bullet and have it pressure tested. I set the timing back up, no change their in temp less it may heat up slightly faster. The vac advance should be ok as I put a new distributor on it a few months back, can test that as well though just to make sure.

Last edited by cebra; 09-14-2018 at 03:18 PM.
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Old 09-14-2018, 03:22 PM   #29
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Re: 350 Heating Up at Stops

Starting to wonder about the radiator as I have tried everything I can think of and/or have read on here. My coolant is 50/50 and looks clean. I have emptied the radiator about once a month for the last 6 months battling this issue. The flex fan vs the clutch fan didn't change anything for me. The clutch fan is pretty far into the shroud where the flex was not but neither fixed the issue. How much does it generally cost to get a radiator pressure tested and will this tell me if the flow is sufficient or if it just has a leak (I know it doesn't)? Thanks for all the suggestions.
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Old 09-14-2018, 04:36 PM   #30
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Re: 350 Heating Up at Stops

Originally Posted by cebra View Post
The clutch fan is pretty far into the shroud where the flex was not but neither fixed the issue.
It's possible that one problem was exchanged for another, and the results ended up about the same. What I mean is:

You started out with a crappy (my opinion) flex fan. It sat in or near the end of the shroud where it should, but its poor design allowed overheating.

Your new clutch fan can't properly do its job if the fan sits too far into the shroud. Instead of pulling air through the radiator, air is simply passing around the fan, between the fan and the shroud.

If you used a spacer (such as the one your flex fan had) with the clutch fan, that might be the problem. The fan clutches I have seen do not use a spacer. Remove the spacer and the fan will be better positioned in the shroud. Probably already posted but the fan should sit at the end of the shroud, roughly halfway in & halfway out.

Any chance you can post a pic or two showing the placement of the fan?
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Old 09-15-2018, 06:48 PM   #31
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Thumbs up Re: 350 Heating Up at Stops

One thing that hasn't been mentioned. Seal off the radiator so the air has to pull through it and not around it. Air is like water it flows to the easiest path. If you have gaps between the radiator and support and shourd close them up with some type of sealer. I use the black foam to seal off around it. It will work wonders for the cooling effect.
Timing will also help if it's not set right.
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