Which carb for L48 vette
04-16-2009, 09:21 AM
#1
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Which carb for L48 vette Well my cousin has a 78 vette and the carb is not fully functioning. It's not opening all 4 barrels. Seems my dad has the smae problem with the new unit he got from jegs. Not sure if this is a common problem. The car is pretty basic just has a full exhaust and maybe a mild cam later down the line. What carb size, choke type, and brand would be a good choice?
04-16-2009, 01:25 PM
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i saw on jegs there are different chokes and sizes 650-750 for the l48. wasn't sure what would be needed. sometimes some brands are not worth the money so i was just looking for an oem replacement that worked well.
04-16-2009, 01:47 PM
#5
I'd imagine a 600cfm would be a good fit. By my cals your engine came out to 558cfm req at 100% VE. It really runs probably closer to 80% though. I'd say 600cfm.
I'm sure some one else will chime in and give you a better answer on what select and why.
~Jim~
I'm sure some one else will chime in and give you a better answer on what select and why.
~Jim~
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04-17-2009, 10:06 AM
#8
check out the holley and barrygrant websites for their tech articles,
http://www.holley.com/TechService/
http://www.gnetworks.com/v4/go.gnf?s...1_i2_w1_f1_001
there is a formula for calculating cfm requirements of the engine but you loosely base your carb decision on it. Really though you don't need it, there's only a handful of different size carbs made to account all the engines out there anyway.
for a stock 350 c.i.d. v-8 engine with normal compression the norm is a 650 cfm carb. The biggest carb you can go is a 750cfm and you would only do that if you're looking to get the most hp at high rpm out of the engine. Also check the articles at popular hotrodding, chevy hiperformance, and gm high techperformance, they have done countless dyno articles of out of the box carbs of 650-750-800 cfm sizes on up to 1000+ cfm, in almost every case the smallest carb gives the greatest tq numbers everywhere but at high rpm with the slightly larger carb giving around 20 more peak hp at most but with big sacrifices in torque at normal operating rpm ranges. This is ok under certain conditions, such as if it's a track only car and the engine is never expected to perform at less than 4000 rpm. But for a street car it would be one of the worst decisions you can make. If your engine is not built to make peak hp at 6000-6500 rpm and above then you will always want to choose the smaller cfm carb that is available.
Carb sizing aside, maybe the more important things to need to decide is whether you want vacuum or mechanical secondaries. This will be based on how you want to drive the car and the transmission type- manual, or auto and what size converter. Read some reputable articles regarding that, I'm not sure off the top of my head.
http://www.holley.com/TechService/
http://www.gnetworks.com/v4/go.gnf?s...1_i2_w1_f1_001
there is a formula for calculating cfm requirements of the engine but you loosely base your carb decision on it. Really though you don't need it, there's only a handful of different size carbs made to account all the engines out there anyway.
for a stock 350 c.i.d. v-8 engine with normal compression the norm is a 650 cfm carb. The biggest carb you can go is a 750cfm and you would only do that if you're looking to get the most hp at high rpm out of the engine. Also check the articles at popular hotrodding, chevy hiperformance, and gm high techperformance, they have done countless dyno articles of out of the box carbs of 650-750-800 cfm sizes on up to 1000+ cfm, in almost every case the smallest carb gives the greatest tq numbers everywhere but at high rpm with the slightly larger carb giving around 20 more peak hp at most but with big sacrifices in torque at normal operating rpm ranges. This is ok under certain conditions, such as if it's a track only car and the engine is never expected to perform at less than 4000 rpm. But for a street car it would be one of the worst decisions you can make. If your engine is not built to make peak hp at 6000-6500 rpm and above then you will always want to choose the smaller cfm carb that is available.
Carb sizing aside, maybe the more important things to need to decide is whether you want vacuum or mechanical secondaries. This will be based on how you want to drive the car and the transmission type- manual, or auto and what size converter. Read some reputable articles regarding that, I'm not sure off the top of my head.
