Carb Dilema
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Mopar Fan
Joined: Jun 2018
Posts: 28
Likes: 8
From: Plano, TX
Carb Dilema
OK, this horse may have been beat to death but here it goes anyway.
I have a 95 model basically stock 5.9 360 in my 37 Plymouth coupe that has been converted to a carb with an airgap intake. Only other modification is a set of long tube headers. The Edelbrock 600cfm that was on it when I bought it was OK nothing special. However, I had an electrical fire and I guess the chemicals in the fire extinguisher caused a lot of corrosion on the body of the carb and it looked like hell. Never could get it to clean up. Buddy had a new Quick Fuel 680 that he was going to use on a build, but changed direction. I have been running the 680 for the time being. Does seem to be too much off idle as it stumbles a bit. At cruise it seems to be OK, but has backfired a time or two when I let off to come to a stop. All that said I am no carb expert by any stretch of the imagination so not sure if jet or accelerator pump changes could solve the issues or not.
Looking for a new carb and when I plug info into the CFM calculators based on 360 with 5500 RPM and use their suggested 83% volumetric efficiency I get 475cfm or at 100% VE it would be 572cfm. Yet multiple 5.9 magnum build articles talk of running 750cfm to as much as 850cfm with decent looking dyno number. I get that most of these have aftermarket heads and upgraded cams, but do those really allow the engine to use as extra 30% cfm boost over what the calculators show as the proper carb for a 100% volumetric efficiency (impossible to reach by the way) carb or are the calculators just wrong or maybe calibrated for a weak Chevy?
What cfm range have you had success running on a fairly stock 360?
I have a 95 model basically stock 5.9 360 in my 37 Plymouth coupe that has been converted to a carb with an airgap intake. Only other modification is a set of long tube headers. The Edelbrock 600cfm that was on it when I bought it was OK nothing special. However, I had an electrical fire and I guess the chemicals in the fire extinguisher caused a lot of corrosion on the body of the carb and it looked like hell. Never could get it to clean up. Buddy had a new Quick Fuel 680 that he was going to use on a build, but changed direction. I have been running the 680 for the time being. Does seem to be too much off idle as it stumbles a bit. At cruise it seems to be OK, but has backfired a time or two when I let off to come to a stop. All that said I am no carb expert by any stretch of the imagination so not sure if jet or accelerator pump changes could solve the issues or not.
Looking for a new carb and when I plug info into the CFM calculators based on 360 with 5500 RPM and use their suggested 83% volumetric efficiency I get 475cfm or at 100% VE it would be 572cfm. Yet multiple 5.9 magnum build articles talk of running 750cfm to as much as 850cfm with decent looking dyno number. I get that most of these have aftermarket heads and upgraded cams, but do those really allow the engine to use as extra 30% cfm boost over what the calculators show as the proper carb for a 100% volumetric efficiency (impossible to reach by the way) carb or are the calculators just wrong or maybe calibrated for a weak Chevy?
What cfm range have you had success running on a fairly stock 360?
Thread Starter
Mopar Fan
Joined: Jun 2018
Posts: 28
Likes: 8
From: Plano, TX
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