pros and cons of carb spacer???

H All...
What are the pros and cons of using a one inch carb spacer?? Why do people use them and some don't? Personal reasons? Performance gains?? Any suggestions or tips or advice will be greatly appreciated...
Rick

 

We usually do not have enough room under a stock hood for them. Otherwise it is cheap HP.

 

I think there's usually enough room for the 1" spacers. I'm adding one to my 350 this spring. I believe the main benefit is improved flow at higher RPM's.

 

They are tuning tools. You have to try all types before you find what works. EVERY engine will respond differently.

 

Also, are you talking about an open spacer, a 4-hole one, or something in between? And what type of manifold, dual- or single-plane?

Generally speaking, an open spacer increases the 'plenum' area under the carb and is good for high rpm, like a single-plane manifold. An individual-hole spacer lengthens the runner area and isolates each carb bore for a stronger signal, good for low-mid rpm. The general idea is that the spacer adds to the effect of the manifold it's on.

On my old 350, a 1" 4-hole spacer under the Q-jet and on the iron manifold made a fairly dramatic difference in the off-idle and cruise throttle response. So much so that I just went ahead and kept it when I swapped the 464 in. I'm thinking of opening up the secondary side into one large hole and maybe cutting the manifold divider down for wot/high rpm, and keeping the primary side individual holes as is for cruise / low rpm.

 

what if you have a 66 340 with 4 holes in your manifold do you need to use a 4 hole spacer? looks like fuel/air mix wouldnt flow as good? any ideas??

 

i'm trying a split front open rear spacer. i made from a pine board so it's 3/4" thick . was going to use two thick but wouldn't clear the hood. made a 4 hole one for the IHC scout cause the factory spacer fell apart. keeps the carb cooler

 

I'll bet if you look into the manifold, the 2 holes on each side both feed right into the same passages, that's pretty standard for stock dual-plane manifolds.

On a 4-hole spacer, the effect on the carb is similar to a one-bore-per-cylinder setup, like a racing weber or something. It makes more of a straight tube/passage right out of the carb bores, which tends to increase the vacuum signal and pressure waves on the carb, which helps throttle response and lower rpms.

Couldn't hurt to try one, as long as you've got the hood clearance, and can hook up the choke and throttle without major mods.

 

So, if i'm running a pretty much stock 350 with a TA stage 1 intake, if I use a 1" 4-hole spacer with an Edelbrock carb, I would gain more umph! at idle & low rpm? Can someone confirm or deny please?