Am I under carbed?

[dandyZ]

SBC with iron vortec heads, zcam,pertronics flame thrower dist., block hugger headers. P.O. built it so I don't have as much info as I'd like. So should I be adjusting my 600 cfm edelbrock carb as rich as possible? Just looking for max power/performance out of this particular set-up. '71 240Z

 

Thanks

[emeraldlion]

sbc doesn't say much. 283, 302, 327, 350, 355, 383 or any combo in between. Anyone who is going to tell you whether you're under carb'd will need to know your CID

[dandyZ]

Sorry, sbc 350

[kiwi303]

A cubic foot is 12"x12"x12" or 1,728ci

 

600 cubic feet is 1,036,800ci (600*1728)

 

So your carb can flow just over a million cubic inches of air to feed your motors 350 cubic inches of displacement.

 

1,036,800ci per minute divided by 350ci per revolution is 2962.2xxx revolutions

 

So by maths and logic, you should run out of efficient flow through the carb at just under 3000RPM and past that things get a bit restrictive.

 

 

 

Using 750CFM instead of 600 as that seems the next common size up gives an eventual peak efficient flow of 3702 revs.

 

 

maths is interesting, but without knowing the port flow numbers and slapping it on the Dyno, the maths is just data... but I would say Probably yes....

[dandyZ]

Thats what I was thinking...

[jt1]

You only fill a cylinder every other revolution.

 

How does the car run now? What are your goals? Chances are you would be better off tuning the carb you've got rather than buying another.

 

jt

[grumpyvette]

this is not a guessing game, having a good understanding of what your looking at and a few basic tools will provide more info,

http://www.harborfreight.com/fuel-pump-and-vacuum-tester-93547.html

throw a vacuum gauge on the plenum under the carb and run the engine at w.o.t. under load and get a reading

if its higher than about 2 inches of vacuum you might benefit from a slightly larger carb.

 

http://forum.grumpysperformance.com/viewtopic.php?f=44&t=777

 

http://forum.grumpysperformance.com/viewtopic.php?f=55&t=2994

Edited October 3, 2010 by grumpyvette

[SBC Z]

a 600cfm carb is plenty for a mild 350

your good!

[John Scott]

So should I be adjusting my 600 cfm edelbrock carb as rich as possible? Just looking for max power/performance out of this particular set-up. '71 240Z

 

Thanks

It wouldn't matter if you had a 100 cfm 1 barrel or a 1050 Holley Dominator. Rich as possible will only foul the plgs and give poor performance.

You want the air fuel ratio, at wide open, to be about 12.8:1 to 13.2:1 for max power regardless which carb you run.

I'll probably get flamed, but the Edlebrock isn't really a performance carb. Great street manners, just not ideal for max power/ max performance. A properly tuned double pumper will give more peak hp and is very streetable. Most don't want to spend the time learning how to tune.

600 cfm is a good size, getting what you have working well together can uncover some hp. Ignition should be dialed in before carb tuning. Time on a dyno or at the track tuning is priceless compared to wondering if a change you made really affected the performance.

Edited October 4, 2010 by John Scott

[Zfan1]

I agree with John, a 600 Edelbrock is a drop on and drive but if you are seeking performance a Holley 600-650 Double Pumper is the way to go.