Carb at high alt

[DoubleDingo]

Yeah, the factory cooling system is up to snuff, as long as everything is working properly.

 

[YakkoWarner]

My 454 with the factory style fan clutch and shroud runs down the highway all day long staying nice and cool, only time I start seeing the temp needle creep up is in traffic. It used to get REALLY hot until I realized someone had put the incorrect fan on (it was a factory correct fan but for an older engine with V belt instead of serpentine belt, so it was pushing air the wrong way). I replaced it and the clutch on the assumption that if they used the wrong direction fan they probably used the wrong direction clutch as well. I did have to switch to an alum. radiator because my original brass core one is leaking and no place around here does that kind of work anymore. My truck came with the factory auxillary electric fan that comes on when the temp comes up to around 180 and it does help - I thought about trying electric fans to stay cooler when stuck in traffic, but right now have more pressing issues to solve.

 

[justhorns]

I live at 5800 feet, and drive up to the hills up to 10,000 all the time. Original cr*p carburetor, and it does fine.

 

[DoubleDingo]

I live at 5800 feet, and drive up to the hills up to 10,000 all the time. Original cr*p carburetor, and it does fine.

Original, does that mean quadrajet? The OP has an aftermarket carb.

 

[squaredeal91]

Original, does that mean quadrajet? The OP has an aftermarket carb.

I noticed that too

 

[Copymutt]

Overheating climbing a mountain

Hello, I’m a longtime reader, first time poster. My 1978 K25 resto project is running great, but it overheats when driving up the Sierra Nevada mountains. Tech stuff: -383 SBC (mercury marine block) -9.5:1 compression -Moderate cam (boat cam) -Summit iron vortec heads. 64cc chambers...

www.gmsquarebody.com

Here is a thread of mine from a year ago.
I have a big new 4 core alum radiator, electric 2700cfm fans.
I’m guessing it’s always gonna run hot because I have a 383 with decent compression and a big lumpy cam.

Other than installing a semi truck radiator, I don’t think there is anything else I can do to improve this cooling system.

A simple low buck fix. Fab a spray bar for front top of the radiator core, simple pipe w/ small holes. Attach to a gallon or 2 water supply & divert your windshield washer pump or any 12v switch controlled pump. The gauge will drop in minutes.

 

[squaredeal91]

A simple low buck fix. Fab a spray bar for front top of the radiator core, simple pipe w/ small holes. Attach to a gallon or 2 water supply & divert your windshield washer pump or any 12v switch controlled pump. The gauge will drop in minutes.

I've actually contemplated doing this for in town with a/c on or for when wheeling trails

 

[justhorns]

Original, does that mean quadrajet? The OP has an aftermarket carb.

No, I have a 250-6 with a Varijet 2. The VArijet is the cr*p.

 

[bucket]

Can you disable the fans while at road speed? An electric fan running at road speed can hurt airflow through the radiator more than when it is off.

 

[jumpjets]

Big updates:
I installed a mechanical fan and it works great!!
-summit racing 7 blade 19” steel fan
-Hayden severe duty clutch
-LMC 2 piece shroud for small block trucks
About $200 altogether.
AC is still cold. I’ve climbed several intense grades in the Sierra Nevada mountains, and never been above 169*. I climbed telescope peak in Death Valley, up to 8200’. It got up to 210 on that climb.

The carburetor is well behaved at high altitudes when it isn’t heat soaked. I just bumped up the idle slightly. No re-jetting required. It smells rich at hi alt, but that’s expected.

The past couple weekends I’ve been adventuring in the sierras and Death Valley.

Now that I have a proper adventure truck….i wish I’d spent the money on a TH700R4 instead of a TH350. I’m getting 6mpg on these long trips.

Thanks to everyone for helping me finish my trail truck!!!!

 

[DoubleDingo]

That's great @jumpjets . Glad you got the cooling problem fixed and in turn a better performing carb.

 

[Ricko1966]

@jumpjets not bagging on you,writing this so it's easy to find in search engine. Another case where the cure to overheating on an electric fan swap was swap back to a mechanical fan. It starts an argument everytime I say it. Most electric fan swaps are not as capable as a mechanical fan.

 

[WFarm]

Look at the shroud on some European cars with electric fans,the actually have rubber flaps that blow open at road speed so the shrouds don't restrict air flow. I'll try to find a pic.

I modified my fan shroud as Rick mentions. Cut several openings and then riveted thin, flexible rubber “flapper valves” over each opening to allow more air flow when at highway speeds.

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