I am in the last stages of tweaking my L48 engine. (Engine rebuild plus new intake, heads, cam, headers, etc.)
The question is what size carb?  The performance shop where I got the parts recommended a 750cfm.  If I use the formula to size what carb to use it comes out to about a 600 - 650.   THe mechanic doing the cylinder work is also wondering if a 750 is too much.  I am using vacuum secondaries of course.
Any recommendations out there, (the upgrades are based on the Edelbrock Power packages for a 350 using the vortec heads).
I want my cake and eat it to, I want great low end torque but good gas mileage when cruising the highway (I do recognize this is a relative term with a vet).
Thanks for any advice.

I know the L-48s came with a 750 CFM and the L-82s came with an 850 CFM (Q-Jets). 'Learned that right here at C3VR!

jr here... in my 78 i have a zz4  complete crate engine(355 horsepower, aluminum heads 10.5 compression) , i originally had a 650 Edlebrock(yeah, insert explitive here) and while i didnt get 'maximum' performance, i did get some great fuel milage with a 4 speed and a 4.10 rear gear(60 mph was around 3200 rpm), about 18-20 mpg.  I since went back to a Holley(insert other explicitive here) 750 Double Pumper, can actually feel the difference in power, and now with the 5 speed overdrive, i'm still getting around 18 or so mpg(60 mph now is around 2100 rpm)...  granted i'm not deeply educated in the subject, but, i would kinda think that an 850 cfm would be a touch tooo much... though, i've been considering about a 900 cfm set up ;) (2-4bbl set up)... still, 750cfm should be more than adequate for 'cruising'  :)

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StingrayJim
NCM Lifetime Member #1936

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Do not OVERSIZE your carb!!!

  With my Banks setup it had a 800CFM 4150 Holley on a 350 CI Engine and it Ran Great on the Dyno. Didn't run worth a darn on the Street a Honda could run away from it  for the first 200 Feet. If You read a Test or Two You will find that Going to a Bigger Carb on a Street Engine only Gains a few HP on Top but gives up a Lot of Drivability that will make it slower on the Street. A 650 and a 350 go well togeather.

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I agree, too much carb is too much. I have a 383 stroker in my wifes car. 430 HP, 460 torque. It has a 750 Edelbrock, and it is right on the verge of being too much carb, I have tweeked with it enough to make it work, but I still may put a 600 or 650 on it.

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One more voice agreeing...  You will be happier with a smaller carb, and the original Q-jet is probably your best choice.

Larry

A 600 cfm carb should be perfect for a street driven car...might go to a 635/650 and still be ok. Bigger is NOT better in this case. All of the above advice is right in line with normal logic...and the math don't lie, either!
If you had a 5.14:1 rear gear, a four/five speed, and a tunnel ram, 12.5 comp ratio, and a killer roller cam, the bigger carb would be ideal...but then you wouldn't be able to actually drive it on the streets comfortably... btdt....

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Joel Adams
C3VR Lifetime Member #56    
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I put a Edelbrock 600 with electric chock and cam/intake on my L-48.  Bought rod/jet kit and build from there. Had no problems.

thanks all
I knew i would get the answers I needed here.
I wondered about the Q-jet but was impatient to wait the several weeks to send it out for re-build.
I will probably send the Q-jet up to the Carb Shop for a re-build once its out (I hear they do about the best job) and that way I'll have it  to test on the car  as well.