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Old 03-28-2021, 05:56 PM   #1
panhead59
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Getting hot issue

Stock 350 in a 68. Coolant temp. Goes up fast over 55 mph. Old issue, nothing new. 160 thermostat, good tight clutch fan with 7 blade fan. Good shroud. Fan 1/2 in, 1/2 out. Runs 170-180 all day long in city. Say below 55. Goes to 220 and probably would go higher if i let it over 55 mph. 50/50 mix coolant. Just changed radiator cap, of course it won't be that easy. Timing set at 10.5 btdc. 12 is too much. Thoughts ?
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Old 03-28-2021, 07:03 PM   #2
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Re: Getting hot issue

The blade, clutch, and shroud have nothing to do with cooling at the speed, so you can rule all that stuff out.

My guess is you need a better radiator.
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Old 03-28-2021, 07:26 PM   #3
'68OrangeSunshine
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Re: Getting hot issue

What radiator are you running?
[Semper Fi]
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Old 03-28-2021, 08:00 PM   #4
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Re: Getting hot issue

Running a 2 row now. Upon further inspection, it is shot. Recommendations?
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1959 H-D Panhead. Owned since 1978. Currently with son in Lawton, OK.
1968 Chevy Custom SWB pick up. Fleetside. Lowered 4/6. Totally refurbished. 1966 Pontiac GTO. 4 speed. Saved original 389. Now has slightly built 455 engine. 355 rear gears. Very fun to drive !
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Old 03-28-2021, 08:12 PM   #5
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Re: Getting hot issue

A re-core of your radiator, if a lot of tubes have been soldered shut in previous work, would be enough. Seems like it's cheaper to buy a new radiator, though. Without AC, I've gotten 2-row radiators from O'Reilly reasonably cheap, like about $200. Of course that was several years ago.
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Old 03-28-2021, 08:44 PM   #6
'68OrangeSunshine
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Re: Getting hot issue

I live in AZ full time. I have a 4-tier core radiator on the 350 V8 in my '71 GMC Jimmy, and a 3-tier core in my '68 C/10 Stepside w/ 292 L6. [I'ts also the wider V8 style radiator, since the narrower L6 radiators became unavailable.] I use a 50/50 Prestone mix in both.
After some high heat issues on the 292, last summer, I flushed the system, put on new hoses and fresh coolant, and it runs fine. The 350 runs cool now too.
Can't remember what degree settings my thermostats are, but they're around 180 - 195*.
Too low a T-stat, and it just opens early, and the water sluices around, without spending time in the radiator to cool off.
For a moderate climate like VA, a 3-tier core might work. Four would be too much.
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Old 03-29-2021, 12:47 AM   #7
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Re: Getting hot issue

When my all-metal 4-row needs replacing, I'm strongly considering a heavy-duty 2-row aluminum radiator.



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Old 03-29-2021, 01:18 AM   #8
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Re: Getting hot issue

Does your truck have a spring in the lower radiator hose ? A collapsing lower hose could explain your symptoms along with a clogged radiator .
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Old 03-29-2021, 05:30 AM   #9
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Re: Getting hot issue

Personally I prefer the old school copper/brass radiator. With the aluminum you need to run the orange coolant.
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Old 03-29-2021, 08:29 AM   #10
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Re: Getting hot issue

Yes on the lower hose spring. Current radiator needs replacing. I went with a Cold Case direct fit alum. Radiator. I've had good results with the one in my GTO (with elec. Fans) so I'll try one in the truck. Minus the elec. Fans. I just bought some Prestone antifreeze that says "recommended for all vehicals makes, models and years." And it is clear
Looks like thick water. They've been around forever, so i guess i can trust their product. I think that green/yellow difference has most likely been improved upon.
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1959 H-D Panhead. Owned since 1978. Currently with son in Lawton, OK.
1968 Chevy Custom SWB pick up. Fleetside. Lowered 4/6. Totally refurbished. 1966 Pontiac GTO. 4 speed. Saved original 389. Now has slightly built 455 engine. 355 rear gears. Very fun to drive !
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Old 03-29-2021, 12:58 PM   #11
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Re: Getting hot issue

Just be aware that Cold Case's "direct fit" is in reality just sort of direct fit and you will have to modify the factory mounts or fabricate new radiator mounts.
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Old 03-29-2021, 03:54 PM   #12
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Re: Getting hot issue

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Originally Posted by panhead59 View Post
Stock 350 in a 68. Coolant temp. Goes up fast over 55 mph. Old issue, nothing new. 160 thermostat, good tight clutch fan with 7 blade fan. Good shroud. Fan 1/2 in, 1/2 out. Runs 170-180 all day long in city. Say below 55. Goes to 220 and probably would go higher if i let it over 55 mph. 50/50 mix coolant. Just changed radiator cap, of course it won't be that easy. Timing set at 10.5 btdc. 12 is too much. Thoughts ?
How old is the water pump. If it's old/worn those can be a cooling issue as they will cavitate more than pump.
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Old 03-30-2021, 06:04 PM   #13
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Re: Getting hot issue

A wide tube 2 row aluminum rad will cool better then a 4 core copper rad
Tstat to low
What psi is the rad cap and is the rad cap any good
A failed rad cap can cause overheat issues as well as worn water pump

I ran green Preston in my 99 for many years no issues
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Old 04-06-2021, 09:23 AM   #14
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Re: Getting hot issue

Update on new radiator. I went with a alum. 2 row from Cold Case. It solved problem of getting hot over 55mph. Old radiator was pretty rusted inside. Cold Case direct fit was just that- direct fit. The weld on top, by drivers side bracket wad/is a little thick. 5 min. Of grinding the top bracket was all that was needed. Fitment wasn't as easy when i put one in my 66 Gto, but very very easy and quick with 68 pickup. I'll put 180 degree thermo. Back in now. Used Prestone antifreeze listed for all radiator materials. It is green in color. I would highly recommend this radiator even though it's a little pricey at around $ 375.00.
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1959 H-D Panhead. Owned since 1978. Currently with son in Lawton, OK.
1968 Chevy Custom SWB pick up. Fleetside. Lowered 4/6. Totally refurbished. 1966 Pontiac GTO. 4 speed. Saved original 389. Now has slightly built 455 engine. 355 rear gears. Very fun to drive !
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Old 04-06-2021, 10:55 AM   #15
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Re: Getting hot issue

I've had that same model radiator in my truck for a couple years. Dropped right in and no trouble! Good to see that the problem is licked.
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Old 04-06-2021, 01:30 PM   #16
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Re: Getting hot issue

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Originally Posted by panhead59 View Post
Update on new radiator. I went with a alum. 2 row from Cold Case. It solved problem of getting hot over 55mph.
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Old 04-06-2021, 04:26 PM   #17
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Re: Getting hot issue

I'm betting on a timing issue. Is the vacuum advance working.
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Old 04-06-2021, 04:34 PM   #18
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Re: Getting hot issue

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I'm betting on a timing issue. Is the vacuum advance working.
$500 says you are wrong.
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Old 04-07-2021, 12:06 AM   #19
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Re: Getting hot issue

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Personally I prefer the old school copper/brass radiator. With the aluminum you need to run the orange coolant.
Been using a 2 row aluminum radiator for 12 years and using Prestone "green" coolant mixed 50/50 with distilled water... No problems...

Gary
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Old 04-07-2021, 01:10 AM   #20
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Re: Getting hot issue

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Been using a 2 row aluminum radiator for 12 years and using Prestone "green" coolant mixed 50/50 with distilled water... No problems...

Gary
OK. Must be an urban myth. Any dis-similar metal corrosion if you have a copper/brass heater core and an aluminum radiator?
I prefer the green Prestone myself.
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Old 04-07-2021, 09:50 PM   #21
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Re: Getting hot issue

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OK. Must be an urban myth. Any dis-similar metal corrosion if you have a copper/brass heater core and an aluminum radiator?
I prefer the green Prestone myself.
Been running green in my Chevelle for 8 or 9 years with an aluminum radiator this is what DeWitt calls for with distilled water. Only had one problem but I dont think the antifreeze was the problem
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Old 04-07-2021, 09:57 PM   #22
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Re: Getting hot issue

Ouch!!
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Old 04-08-2021, 01:24 AM   #23
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Re: Getting hot issue

Ouch, too.
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