350 sbc heat soak

ASharpShark

Not-quite-so-new-guy
Jun 14, 2020
11
3
Hi, im Jaden and own a 82 Monte Carlo. Ive owned the car for about 4 years and recently have swapped the motor from the stock 267 to a built 350. This motor has been giving us troubles since we bought it pre-built at a swap meet in November 2021 and it went through a rebuild around February 2022. The cars runs pretty decent with some torque to it but after turning off the car and letting it sit for more then a minute the temp rises pretty quickly to around 230~ while the car is off. When you go to fire up the car after letting it sit for a few minutes it cranks for about 15 seconds, maybe more, and once it finally starts it dumps raw fuel causing white smoke and runs flooded for about a minute or two until it clears up and goes back to normal. It has a Cold Case large 2 row radiator with dual electric 12" fans, stock water pump, and no thermostat currently. I have been dailying this car for weeks and am sick of this issue and the car running hot in general. Today while driving the temperature reached up to 200F which is strange because it doesnt even get above 190 while driving at all. My dad has owned multiple gbodys and classics in general and we are stumped on this issue. Any and all help is appreciated, i will answer any questions in hopes of curing this heat soak/overheating! Also, the car has had the rear end swapped from its stock low 2.41 ratio gears to what I thought was 3.73 gears with a posi but the car tops out at 50-55, im thinking the rear end may be closer to 4.10 gears or even 4.56s, will gears this high cause overheating due to higher rpm from the gears? Edit: I forgot to mention that you can hear the gas in the carburetor boiling away and after a little bit of time the fuel filter is completely empty. I have yet to see if the carburetor spacer affects this.
 

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ELCAM

G-Body Guru
Jun 19, 2021
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pagrunt

Geezer
Sep 14, 2014
7,870
113
Elderton, Pa
Need a thermostat to help regulate block temps so the fans can work when needed. Also how's the coolant mix, 50/50, not near 50/50, straight coolant, straight water?
 
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565bbchevy

Geezer
Aug 8, 2011
9,126
113
Michigan
That radiator looks really thin for a 2 row, any idea what size tubes they use?
Also are you running a phenolic spacer under the carb?
 
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ASharpShark

Not-quite-so-new-guy
Thread starter
Jun 14, 2020
11
3
Need a thermostat to help regulate block temps so the fans can work when needed. Also how's the coolant mix, 50/50, not near 50/50, straight coolant, straight water?
Having the thermostat before had the temperature about 10-20 degrees hotter but i have changed a few things so i will try that soon. The coolant is 50/50 green coolant with distilled water and a bottle of water wetter.
 

ASharpShark

Not-quite-so-new-guy
Thread starter
Jun 14, 2020
11
3
That radiator looks really thin for a 2 row, any idea what size tubes they use?
Also are you running a phenolic spacer under the carb?
Per cold case's website it states "(2) 1.25 inch Tubes. Within the last hour i added a 1 inch spacer i got from autozone. The spacer helped a little bit with response and driving but it still had heat soak and cranked for 6+ seconds til starting sounding like it was flooded. This was after letting it sit for 5 minutes. Also the top row on the radiator is not the thickness of the radiator, it is just a hollow chamber for the fans to mount onto.
 

565bbchevy

Geezer
Aug 8, 2011
9,126
113
Michigan
Per cold case's website it states "(2) 1.25 inch Tubes. Within the last hour i added a 1 inch spacer i got from autozone. The spacer helped a little bit with response and driving but it still had heat soak and cranked for 6+ seconds til starting sounding like it was flooded. This was after letting it sit for 5 minutes. Also the top row on the radiator is not the thickness of the radiator, it is just a hollow chamber for the fans to mount onto.
This is the Griffen I installed in my Regal with 2 x 1.25" tubes and you can see how thick it is.
 

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565bbchevy

Geezer
Aug 8, 2011
9,126
113
Michigan
Also I would replace that alternator belt ASAP and change out that aluminum carb spacer with a phenolic one if you want to help eliminate heat soak to the carburetor. IMO Jomar Performance has the best phenolic carb spacers and I have used many different styles and materials.


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64nailhead

Goat Herder
Supporting Member
Dec 1, 2014
4,830
113
Upstate NY
Do you have a chin spoiler?

What temp thermostat?

What carb?

What's the timing - base, vacuum advance, and all in? Are you using ported or full manifold as a vacuum advance source?
 
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abbey castro

G-Body Guru
Oct 31, 2015
668
93
Harker Hts TX
I would go for the following:
1. Install 180 degree thermostat.
2. Check timing

I run 180 degree thermostat, original 87 AC equipped radiator with and oil cooler, trans cooler in front of it and dual Chrysler e-fans that come on at 180. Drove the car this week with over 102 F outside temp and never got to over 190. I bet the timing is off.
 
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