500 cfm too small?
#1
500 cfm too small?
Im currently running a 500 cfm edelbrock carb. But im wondering if its too small? Here are my engine specs.what do you guys recommend?
390 bored over 30
Comp cams 270 magnum cam
Msd ready to run dizzy
Hooker headers
performer intake
Slightly ported c8AE-H heads
10.4 compression
3:50 posi
stock c6 and convertor
This is my weekend only hot rod truck so fuel economy is not a concern
390 bored over 30
Comp cams 270 magnum cam
Msd ready to run dizzy
Hooker headers
performer intake
Slightly ported c8AE-H heads
10.4 compression
3:50 posi
stock c6 and convertor
This is my weekend only hot rod truck so fuel economy is not a concern
#5
#7
600 cfm is more than enough for your motor, on a mildly built street 390 a 600 will have better low end response, and fuel mileage then the 750.
The trick is to tune the carb to the motor, it's not that hard to do... if you're not racing you will never use all the flow that the 750 has.
Most guys make the mistake of "over carbing", don't be that guy.
The trick is to tune the carb to the motor, it's not that hard to do... if you're not racing you will never use all the flow that the 750 has.
Most guys make the mistake of "over carbing", don't be that guy.
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#8
#9
Yeah, find a CFM formula or calculator and you'll be surprised how little is required.
But I think 500 on a nearly 400 CID is on the small side.
I put a 625 cfm on a 351W with aluminum heads, planning 5500 rpm. So far I've only broke in the cam and haven't really driven it yet.
I had a 750 double pump, mech sec. On a Windsor, 400 and a 460. Great carb. But Very thirsty.
But I think 500 on a nearly 400 CID is on the small side.
I put a 625 cfm on a 351W with aluminum heads, planning 5500 rpm. So far I've only broke in the cam and haven't really driven it yet.
I had a 750 double pump, mech sec. On a Windsor, 400 and a 460. Great carb. But Very thirsty.
#10
To the OP,
Holley has an interactive carb sizing calculator. Follow the prompts based on your engine and it'll provide recommendations.
I went through it for your rig (with some assumptions like 5500 max RPM, about 396 cubes, and vacuum secondaries given these rigs' portly weight) and the results indicate 600 cfm would be the minimum.
Here. Give 'er a try: Holley Interactive Carburetor Selector
Holley has an interactive carb sizing calculator. Follow the prompts based on your engine and it'll provide recommendations.
I went through it for your rig (with some assumptions like 5500 max RPM, about 396 cubes, and vacuum secondaries given these rigs' portly weight) and the results indicate 600 cfm would be the minimum.
Here. Give 'er a try: Holley Interactive Carburetor Selector
#11
To the OP,
Holley has an interactive carb sizing calculator. Follow the prompts based on your engine and it'll provide recommendations.
I went through it for your rig (with some assumptions like 5500 max RPM, about 396 cubes, and vacuum secondaries given these rigs' portly weight) and the results indicate 600 cfm would be the minimum.
Here. Give 'er a try: Holley Interactive Carburetor Selector
Holley has an interactive carb sizing calculator. Follow the prompts based on your engine and it'll provide recommendations.
I went through it for your rig (with some assumptions like 5500 max RPM, about 396 cubes, and vacuum secondaries given these rigs' portly weight) and the results indicate 600 cfm would be the minimum.
Here. Give 'er a try: Holley Interactive Carburetor Selector
Cool link thanks
#12
To the OP,
Holley has an interactive carb sizing calculator. Follow the prompts based on your engine and it'll provide recommendations.
I went through it for your rig (with some assumptions like 5500 max RPM, about 396 cubes, and vacuum secondaries given these rigs' portly weight) and the results indicate 600 cfm would be the minimum.
Here. Give 'er a try: Holley Interactive Carburetor Selector
Holley has an interactive carb sizing calculator. Follow the prompts based on your engine and it'll provide recommendations.
I went through it for your rig (with some assumptions like 5500 max RPM, about 396 cubes, and vacuum secondaries given these rigs' portly weight) and the results indicate 600 cfm would be the minimum.
Here. Give 'er a try: Holley Interactive Carburetor Selector
#14
Some formula I read about a long time ago... Not sure if it is accurate or not.
Find the displacement first.
390 bored .030 over. Stock 390 - 390 bore 4.052 in stroke 3.784 in
Bore squared - 4.082^2 = 16.663 then multiplied by the stroke - 3.784 = 63.052 then multiplied by .7854 = 49.52 times the number of cylinders (8) =
396.2 cubic inches.
Take your cubic inch and convert it into cubic feet. Divide by 1728.
396.2 / 1728 = 0.229
Then reduce that number by half because the crank turns over twice to fire all of the cylinders.
0.229/2 = 0.1146
Then multiply that by the maximum RPM you want to run.
0.1146 x 5500 = 630.52 CFM.
So you would need no less than a 630.52 CFM carb.
Hope this helps you some.
Find the displacement first.
390 bored .030 over. Stock 390 - 390 bore 4.052 in stroke 3.784 in
Bore squared - 4.082^2 = 16.663 then multiplied by the stroke - 3.784 = 63.052 then multiplied by .7854 = 49.52 times the number of cylinders (8) =
396.2 cubic inches.
Take your cubic inch and convert it into cubic feet. Divide by 1728.
396.2 / 1728 = 0.229
Then reduce that number by half because the crank turns over twice to fire all of the cylinders.
0.229/2 = 0.1146
Then multiply that by the maximum RPM you want to run.
0.1146 x 5500 = 630.52 CFM.
So you would need no less than a 630.52 CFM carb.
Hope this helps you some.
#15