Carb Spacers??
 

Has anyone had experience on adding a 1" or 2" carb spacer?

Are there any negative effects such as changing the AF numbers or leaning out the motor?

Any power gains??

Small Block 350
600cfm carb
Mild performance upgrades
Alpha One
Laser II 21"
Approx 64 mph @ 5100 rpm

:)

I have a lot of experience with spacers.

Please give me all details:
Holley, Edelbrock or ??? carb ? Vacuum or mechanical secondary ?
intake manifold - exact type
cylinders heads and if any and what work done to them
camshaft - part# and specs
compression
exhaust
What rpm are you spinning at WOT (edit in: saw 5100rpm)

Some Specs
 

WOT 5100rpm 64MPH GPS

GM 2bolt main block
Cast Crank
Edelbrock Perf 600cfm marine
Scat Rods 5.7 Pressed Pin forged
TRW L2256F + .030 Pistons Forged
Melling's M55Hv Oil Pump
Vortec 12558060 - SD8060A Heads
Comp Roller Tip cc1417-16 Rocker Arms
Comp Cams XM270HR Roller Cam http://www.compcams.com/Company/CC/c...?csid=202&sb=2
Hydraulic Roller Lifters
Cloyes True Roller timing set
Edelbrock 7516 RPM Air Gap
Crane Ignition HI-6M
Clevite Bearings
ARP Fasteners
GLM Aluminum Semi Tuned Exhaust Manifolds

1" open spacer if you can fit it . Don't take away flame arrestor size to fit it. Good flowing arrestors are priority.

Do you have the carb tuned in real well ? Have you played with secondary opening rate ? Can you confirm they (secondaries) are wide open at top speed ?

The open spacer will typically need 2# higher jet on a Holley carb. I haven't tuned an Edelbrock on a like combo.

To beat you to the HP question, 8-12hp depending on your carburetor tuning abilities.

Thanks
 

Yes, i currently have a KN 8" flame arrestor. I ran the carb with the out of the box jets, metering rods and springs but do have the calibration kit available. But seeing that it will only gain 12 hp at max, this would only give me maybe around .5 mph gain. Maybe not worth it.

SB,
Is it somewhat rule of thumb open spacers for a dual plane and 4 hole/HVH for a single plane?
I am using a Weiand Stealth with 1" open and a thinking of going to a Dart single over the winter.
I know that spacers are more of a tuning tool.
Just curious,
Thanks

Yes. The HVH SuperSuckers are designed for single plane intake manifolds, so that one is a given.

If the thread starter had a Holley 750, then the spacer would not do much as the 750 would be more than enough carb to feed the motor. The 600 is a little shy and thus using an open spacer would not just create a little more plenum, but more importaantly expose more throttle blade area to each cylinder. Dual planes have divided plenums, thus only letting each cylinder see half the carb. Air gap style with windows in the divider help a little but not a lot.

Also, dual planes have an abrupt change of air direction from base of carb to the intake runners. Raising the carb gives the air a little longer path to make the turn and thus making it a little more gradual.

Air has mass, it doesn't really like to turn/twist, etc. Fuel has lots more mass, and really doesn't do well with turning/twisting, etc.

i have HVH SuperSuckers on my 540 dart single intake go 18hp on the dyno:drink:

Open spacers generally add hp at the top end. 4 hole spacers usually add signal to the carb and help idle and low end. The tapered spacers are crapshoot, sometimes help sometimes not. They caused my engines to lean way out.

Did you re-tune the carbs ?

That is kinda weird because in my experience the tapered spacers usually pull more fuel out of the carb. Basically from straightening the airflow, especially beneficial when running a bigger carb than would be 'standard' for a given engine.

I realize schit happens, not everything is explainable, but I never ran into your circumstance unless something really mismatched like a 2" spacer on a low rpm smaller motor.

Just interested in your data.....more is better. Will lessen the brain cramps...LOL.