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overheating question

General engine tech -- Drag Racing to Circle Track

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Circlotron
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Re: overheating question

Post by Circlotron »

mag2555 wrote: Sat Apr 17, 2021 6:53 pm The fact is that if your pump pressure at whatever given rpm is not higher then your average system pressure then how do you expect coolant to move thru the motor?
The vapour pressure of the coolant is the same on both sides of the pump so it would have no effect on flow rate. It's when the pump starts rotating the pressure on the outlet side increases and the inlet side reduces so the coolant flows.
Belgian1979
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Re: overheating question

Post by Belgian1979 »

Did some tests. Ignition timing had no effect I could tell on the coolant temperature.

I think what Jeff says is correct. The opening point is 195°F and seemingly the full open is at 205°F. It seems to want to hover around 205 but it will heat up further after some time. I thought the full open was at 195°F.
I set the fans up so that the first fan starts up at 207°F and the second at 210°F.

I do know from previous tests my engine is happier at around 195-200°F. I have tried a 180°F thermostat before but it seemed to have a negative effect on the way it runs and idles. I can imagine with a carb this may be different.
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Re: overheating question

Post by BCjohnny »

Belgian1979 wrote:Now, I have upgraded the rad in the sense the heaviest core is in it (still copper though) ......
Although regional terminology varies, I can't recall had a situation related solely to a cooling system issue and not other external factors where a 'high density', otherwise known locally as a 'diesel', core has not made a significant difference

Four row copper/brass, horizontal straight cooling fins, not the ziggy zaggy ones, has normally worked ...... all things being equal
"If an honest man is wrong, after demonstrating that he is wrong, he either stops being wrong or he stops being honest." Anon
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Re: overheating question

Post by stealth »

Please define overheat... is there a temp you are refereeing to or simply pushing water from cap?
The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man.
Belgian1979
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Re: overheating question

Post by Belgian1979 »

stealth wrote: Mon Apr 19, 2021 12:28 pm Please define overheat... is there a temp you are refereeing to or simply pushing water from cap?
For me: going much over 205-210°F. Not like when it's too late. I realize I should have said: running hot.
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Re: overheating question

Post by steve cowan »

What side of the radiator are your fans,are they pulling or pushing air??
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Re: overheating question

Post by Tuner »

Belgian1979 wrote: Mon Apr 19, 2021 12:45 pm
stealth wrote: Mon Apr 19, 2021 12:28 pm Please define overheat... is there a temp you are refereeing to or simply pushing water from cap?
For me: going much over 205-210°F. Not like when it's too late. I realize I should have said: running hot.
Have you confirmed this with some other means, non-contact infrared thermometer gun or ?
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Re: overheating question

Post by NewbVetteGuy »

I know the C3s are "bottom feeders"; I don't think it matters for IDLE and low speed cooling much at all, but are you referring to the PaceCar style front air dam, or the rubber "HD01" "Heavy Duty" cooling package's rubber air dam extension?

Knowing how meticulous you are with the details, I'm assuming you have installed the rad-to-support seals and you have an actual fan shroud and not just fans attached directly to the radiator without the shroud?

What's your coolant-to-water ratio? Pressure rating of your rad cap? -In the Belgian weather, I'd think you could go with a pretty water heavy mix to optimize cooling and a higher pressure cap to prevent boiling.


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Re: overheating question

Post by NewbVetteGuy »

I think I'll regret this when going over speed bumps, but I used a cheapish Amazon generic rubber universal spoiler extension kit to extend my PC spoiler down another 2 1/2 inches. It costs the same $75 as the HD01 style air dam extensions and I think it looks way better on the PC bumper cars... (Ignore where I put two screw heads through the front of the spoiler, please. UGH!)

Note: When ordering a PC spoiler on 78 and 79 cars, even if you ordered or had the HD01 Heavy-duty Cooling option, GM would NOT include the rubber air dam extensions. They deemed the air dam extension only necessary when you did NOT have the PC spoilers. (But HD01 did come with the electric fan to help out the engine fan for low speed cooling.) -Your current setup sounds really similar to the stock "good cooling" on the car, even better with your intake mods so I'm guessing it's just your thermostat not opening all the way until the engine is already 200+F.

Image

Image

I'm using a 75/25 water-to-coolant mixture, with water wetter and anti-corrosion agent to make up for the high % of water. -It's actually a blend of VP's Stay Frosty High Performance Coolant and their Race Coolant which is just a pre-mix of their anti corrosion + water wetter stuff; it's definitely a rip-off but sometimes I just want to hit the "easy button" on something...

That puts my freezing point at -12.5F (which Seattle NEVER gets to and certainly not in my insulated garage), and what would be a boiling point of 218F except when I add a 16lb rad cap pressure that ups the boiling point to 266F or so, I think (boiling point increases 3 deg for every 1 PSI in pressure).

I went with the Mr. Gasket 4364 High flow 180F thermostat for $18.40 which is a rebranded Robert Shaw, then drilled the 3 holes in it like the Evans one and an Ebay Chinese PRW Polished aluminum high flow Corvette style pump -scratch and tent version for $140 -smoothed out the internal casting roughness, and added the CVF Racing Alum 2 groove pulley to it. Chinese 3 row Champ radiator w shroud, single SPAL 16" 30102049 2024 CFM 19 amp fan and seals.

-I've also got my Holley temp probe in the driver's side head; I still need to wire up my relays and figure out how to get the Holley to control it.

I'd like to add a Trackspec hood louver, but they only make them for the L88-style hoods.


Adam

P.S. A Belgian using Fahrenheit... Weird....
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Re: overheating question

Post by Tuner »

P.S. A Belgian using Fahrenheit... Weird....
He is being tolerant and polite to the provincials. :)
Circlotron
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Re: overheating question

Post by Circlotron »

I always thought it would be a good idea, particularly with ECU controlled fans, to have them come on at a quite low rpm when the car is stationary and the temp is over say 190 but but below the main turn on temperature. Have just a small breeze of air wafting through the radiator like the old days of non-clutch fans. Why let it creep up to the trip point unnecessarily?
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Re: overheating question

Post by dannobee »

Circlotron wrote: Mon Apr 19, 2021 11:16 pm I always thought it would be a good idea, particularly with ECU controlled fans, to have them come on at a quite low rpm when the car is stationary and the temp is over say 190 but but below the main turn on temperature. Have just a small breeze of air wafting through the radiator like the old days of non-clutch fans. Why let it creep up to the trip point unnecessarily?
A lot of them already do that. You turn on the A/C and the ECU commands the cooling fans on, and it ends that big swing on the temp gauge that scares some people.
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Re: overheating question

Post by Belgian1979 »

steve cowan wrote: Mon Apr 19, 2021 4:00 pm What side of the radiator are your fans,are they pulling or pushing air??
Pulling
Belgian1979
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Re: overheating question

Post by Belgian1979 »

Tuner wrote: Mon Apr 19, 2021 4:55 pm
Belgian1979 wrote: Mon Apr 19, 2021 12:45 pm
stealth wrote: Mon Apr 19, 2021 12:28 pm Please define overheat... is there a temp you are refereeing to or simply pushing water from cap?
For me: going much over 205-210°F. Not like when it's too late. I realize I should have said: running hot.
Have you confirmed this with some other means, non-contact infrared thermometer gun or ?
Not yet. Need to get a new battery for the gun.
However I think the sensor is good and calibrated correctly as it reads the same as the IAT and ambient air temp when first wanting to start the car.
Last edited by Belgian1979 on Tue Apr 20, 2021 2:30 am, edited 1 time in total.
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Re: overheating question

Post by Belgian1979 »

NewbVetteGuy wrote: Mon Apr 19, 2021 6:49 pm I know the C3s are "bottom feeders"; I don't think it matters for IDLE and low speed cooling much at all, but are you referring to the PaceCar style front air dam, or the rubber "HD01" "Heavy Duty" cooling package's rubber air dam extension?

Knowing how meticulous you are with the details, I'm assuming you have installed the rad-to-support seals and you have an actual fan shroud and not just fans attached directly to the radiator without the shroud?

What's your coolant-to-water ratio? Pressure rating of your rad cap? -In the Belgian weather, I'd think you could go with a pretty water heavy mix to optimize cooling and a higher pressure cap to prevent boiling.


Adam
Hi adam,

It's the Pace car spoiler.
I might be mistaken but wasn't the electric fan an addition for when you have both HD cooling and AC? Mine doesn't have AC to deal with. I cannot mount that fan because the original radiator shroud has been removed since I put electric radiator fans in place. A disadvantage of the electric radiator fans is that it blows less air over the engine like with the factory fan. So it has a tendency to get hotter (especially due to the headers in the car)

All seals are in place to prevent escape around the radiator support and around the fan shroud. The shroud was custom made and envelops the entire core.
I should look the ratio up, but believe it is good to -20°C (-4°F). It's the old red type fluid and I believe it is 50/50 mix.
Cap is a regular style Corvette C3 cap. Coolant pressure is usually around 15 -18 psi.
Temps are in the -10°C in worst case scenario's in winter to 38°C during some moments in summer (10°F to 100°F)
Last edited by Belgian1979 on Tue Apr 20, 2021 2:29 am, edited 4 times in total.
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