Carb at high alt

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jumpjets

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I’m looking at doing some high altitude overlanding in the Sierra Nevada mountains. I live at 2000 feet MSL, and I’d like to drive up to 10,000feet MSL.
Are there any quick hacks I can do to keep the engine alive at that altitude?
it’s a 383 with an edelbrock 600 carb
 
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fast 99

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Carter-Edlebrock metering rods can easily be changed. You will need larger rods. How much reduction in fuel? Someone will come along with the calculation.
 
Rustisbest

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You can download the instructions on Edelbrocks website that'll have the chart that tells you which combo of jets and metering rods you want. 1405 and 1406 are calibrated a little different.
 
85K304SPD

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Like Rustisbest said, it will depend on if it is a 1405 or 1406, but probably at least 3 stages lean. At 2000 you should already be at 1 stage lean, so maybe plan on making a rod change once you get up in the mountains. Try to figure out which rods you will need to change to without having to do a jet change, if possible. Probably run the secondary jet at least 3 stages lean, before you leave. It will also depend on what kind of load you will be carrying or pulling. The edelbrock manual will tell you how to figure it out.
 
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Cool thanks guys. Do you think leaning it out would help with heat buildup as well? The motor quickly gets up to 230* when climbing. Is that normal?
 
85K304SPD

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Leaning it out will make it run hotter. Maybe your radiator is not flowing well, or you dont have a fan shroud. What thermostat are you running?
 
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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 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.
 
85K304SPD

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It could be those electric fans restricting air flow through the radiator. Did you get a good old fashioned manual temperature gauge on there to make sure that the factory gauge is correct?
 
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Your shroud is blocking air flow through the radiator. If the fans are against the radiator you don't need a shroud,the shroud is for when the fans are back from the radiator and the shroud helps distribute the low pressure area across the whole backside of the radiator. 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. Keep looking back I'll post one when I find one.
 

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jumpjets said:

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 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.
Click to expand...
454 with compression and big lumpy cams don't overheat ,you can get a 383 to run cool. I'd be tempted to try a factory shroud and fan and see what that did.If it runs cooler then you will know you need to create more air flow
 
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jumpjets

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I threw away the giant factory wind tunnel shroud and hard mount fan a couple years ago.
I always assumed the airflow would blow right thru the fans at highway speed.
I’ll either look around on summit for a better shroud or just cutting some wind flaps in my current setup.

or could I remove my aluminum shroud altogether and mount my 2 fans directly to the radiator core?
 
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Ricko1966

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I'd try mounting the fans directly to the radiator,but still doubt your electric fans are capable of moving as much air as a mechanical fan and proper shroud. Flexalite recommends a mechanical fan if towing or on 4 core radiators.
 
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jumpjets said:
I threw away the giant factory wind tunnel shroud and hard mount fan a couple years ago.
I always assumed the airflow would blow right thru the fans at highway speed.
I’ll either look around on summit for a better shroud or just cutting some wind flaps in my current setup.

or could I remove my aluminum shroud altogether and mount my 2 fans directly to the radiator core?
Click to expand...
I saved you hours of reading. This guy tried everything. Look at his 1st post vs. What fixed it.
 

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J

jumpjets

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So, I should just convert back to a mechanical fan and the giant wind tunnel factory shroud?
I guess the physics check out on that. My new 2023 RAM 2500 has a mech fan, and it never gets hot, even when towing heavy up serious grades.
Should I use a clutch or direct connection flex blade fan? I’m finding all these parts on eBay for cheap.
 
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jumpjets said:
So, I should just convert back to a mechanical fan and the giant wind tunnel factory shroud?
I guess the physics check out on that. My new 2023 RAM 2500 has a mech fan, and it never gets hot, even when towing heavy up serious grades.
Should I use a clutch or direct connection flex blade fan? I’m finding all these parts on eBay for cheap.
Click to expand...
Fan clutch. And there's a bunch of info on the net about fans that have the most CFM some guys are running some ford mechanical fan,the guy in the post I screenshot is using a fan from a 6.0 express van. Further reading reveals Summit recommends a mechanical fan on 4 cores also From what I can tell the best electrics only pull 5000 cfm and average mechanical fans can do more than that. And I think pretty much any factory truck with a tow package runs a mechanical fan. As to the power loss,not much if you have a fan clutch,and even electrical fan is not free horsepower,it still is a significant draw on the battery so the alternator robs power to generate more amperage.
 
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