hi so ive got a small block and im trying to find out what carb would work the specs are as follows
880 vortec block bored .030 355cu
flotek 190cc heads 64cc chamber
292h cam .501 lift
holley dominator intake manifold
eagle rotating assembly 10:1
light nitrous kit eventually
ive been seeing people say that 650cfm would be enough for a street build but forums also say that more modified engine would need more cfm. the summit calculator is 620 for a street/stock and 790 for a racing application. should i go with a 750 or a 650 looking at a max performance summit carb which is a copy of the holley 4150 it has mechanical secondaries

 

We really need some more information:

-Camshaft Duration @0.050" for both the Intake and Exhaust Lobes.
-Camshaft Lobe Separation Angle, and the Installed position relative to the Intake Lobe Center Line.
-Which Holley Intake-Manifold... the Dual-Plane Street Dominator, or the Single-Plane Strip Dominator.
-What Transmission is being used.
-Torque-Converter or Clutch Specs.
-Vehicle weight.
-Differential Gear Ratio.
-RPM where Peak Torque occurs.
-RPM where Peak HP occurs.

...and if you know what the Average and Peak HP and Torque Numbers are!

 

so these are the cam specs
Intake Duration at 050 inch Lift:
244
Exhaust Duration at 050 inch Lift:
244
Duration at 050 inch Lift:
244 int./244 exh.
Advertised Intake Duration:
292
Advertised Exhaust Duration:
292
Advertised Duration:
292 int./292 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:
0.501 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:
0.501 in.
Valve Lift with Factory Rocker Arm Ratio:
0.501 int./0.501 exh.
Lobe Separation (degrees):
110
The manifold is a single plane strip dominator
the transmission being used is a cd009 nissan manual 6-speed close ratio
this is the clutch kit https://www.z1motorsports.com/z1-pro...0669b9a1c89d96
it says its rated for 500lbs
vehicle weight with engine installed is around 3400lbs
rear diff ratio is 3.53
i expect peak hp to be in the 6000 range im going for a 6800 to 7000 redline
peak torque will probably be around high 4s to mid 5s
hp will be around 425 to 440
torque will be in the range of low 400s

 

The old Comp 292 Magnum cam...

With a large-plenum intake, the 650 is probably the better choice. Esp if your nitrous is wet. The carb sees less "pulsation" in its flow from the intake of each individual cyl.

With a dual-plane intake, a 750 would be a better choice.

Looks to me like not the best choice of intake in any case. Not enough motor or gear for that. It'd most likely run better with a Performer RPM and a 750. Probably make about the same power at the peak, just, better running all-around.

 

I'll see that, and raise you to a short-runner injection system. Call, anyone?

 

In my opinion smaller carbs are safer/easier to tune and larger can make more top end, so it depends on your use. As often happens with the sbc people build for top end power and that makes their low end/drive-ability suck, so they LS swap. Some know how to make large carbs pretty streetable but it's more than just messing with the carb.

 

Q-Jet is my carb of choice. Up to 850 cfm and it can run on a 4 cylinder and still work correctly without being too much carb. I know them like the back of my hand and what needs to be modified to work with different combinations though.

 

Well...
I mean the Older Cam Lobe Design is not doing the Engine any favors...
and the Single-Plane Intake-Manifold is a Miss-Match for the rest of the Engine Build...

I would see if anyone offers a smaller than 750 cfm Carburetor with Annular-Boosters.
It probably wont make a huge difference anyway ...with the Parts that the Engine is currently using.