is a 600 cfm carb too big for a stock lg4 with only the intake changed (edelprock performer eps)


What carb would you recommend besides the quadrajet
for my engine, i have a vacuum advace distributer and since i live in canada i dont have to worry about emissions.

 

a 600 is fine

 

600 is about right for a mild 305 or 350.

If you have a manual trans, I'd suggest a double pumper.

 

thanks guys

 

You can compute for the optimum airflow capacity of a carburetor for a particular engine with this formula:

<displacement> X <max rpm> / 3456 = cfm required

So, for a 350 cid engine revving to 6000 rpm, the equation works out to:

350 X 6000 / 3456 = 607.64 cfm

So a 600 cfm carb is just right.

Using the same formula, a 327 revving to 8000 rpm would want 757 cfm.

Happy calculating to all!

Mike in Manila

 

That's weird...

Part of the formula was deleted by the time it hit the board.

The formula for cfm required is:

displacement (cubic inches, please) X max rpm / 3456 = cfm

Mike in Wonderland

 

when doing the calculations it gives me 485cfm for my 305 is a 600 cfm carb would still be ok

 

Yes.

 

If you install a carb that flows less than what is required, you will be robbing yourself of a bunch of horses. I think they used to hang people for that.

On the other hand, if you install a grossly oversized carb, the chances are you are merely robbing your bank account and paying for something you don't need. But there are other downsides to installing an oversized carb.

A carburetor is most efficient at WOT (wide open throttle). In this state, airflow restrictions are minimized, i.e. the throttle butterfly presents its minimum profile to the air flowing past. A particular carburetor would be optimized in this condition.

If you run an oversized carb, optimum airflow would be attained at partial throttle opening. Opening the throttle further would give no benefit. In fact, you'd probably find a big hole in your performance, something like falling off the edge of the world if the carb was extremely oversized. The world IS flat!

I haven't bought any carburetors lately but I know Holley used to make 'em in 390, 500, 600, 650, 750, etc. sizes. Smaller is usually cheaper so don't pay for more than what you need. You will be richer and faster.

Mike in Manila

 

thanks mike