I know it results in better fuel atomization, better mixture. What is the result of that? Better low-end torque? or what???????????

lets fuel flow better which i guess is suppose to increase the top end...

i've heard people say they feel a different/they don't.

take a gamble but i know clearance issues wihtt he hood may be something to worry about

there are several reasons for spacers...

some are for dual plane intakes. to give it a lil volume for both to feed, some are for a bit more intake volume period.. and others are more practical.. as in to get a 4150 holley to clear the shortsighted edelbrock vacuum port under tha back bowl


BTW the spacer is the best reason to put a cowl hood on

performer rpm + 1" Spacer= bowl vents hitting hood... so cowl is necessary... ... 4" of cowl for propper clearance of the air cleaner

Depending on the material used, a spacer will act as an insulator keeping the carb cooler.

Got a cowl hood. no clearance problems anywhere. Just wondering what to expect. So far, no one seems to know.....(performance-wise) I'm assuming it will function as an inexpensive tunnel-ram which does.........?

Like stated the spacers can have an insulation effect. Some are made of plastic (actually called Phenolic) these offer a decent insulation since the heat from the intake can't transfer directly as easy through the spacer to the carb. Kind of think of it like as the motor heats up oil hits the intake and heats it which turns your carb to a oven for all the air and fuel coming through it. But by insulating the carb from the intake you don't transfer as much heat to the carb. There are aluminum spacers but of course they transfer more heat than the Phenolic ones (10 times more). I have even seen some wood spacers before to reduce heat transfer.

Ok that pretty much materials.

Ok for function wize you mainly have 3 different types of spacers. 4 hole types where the spacer have 4 holes (duh) that go to the venturi. This is suppose to boost the signal to the carb letting it get a more procise stronger signal so it feeds the motor better. I read once in a Car Craft Mag that most people assume they need a bigger carb when they really just need to boost there signal to the carb and the smaller one would work fine. Of course they say they don't breath as well as open spacers in the high RPMs.

The other type is a open spacer. It's just a hollow'd out spacer which boosts your intake volume. Kind of a way to turn a small intake into a slightly bigger one mimicing a single plane type. These don't increase your signal to the carb since you're putting a lot of space between the carb and intake. Suppose to work well in high RPMs, but can suffer sometimes in low RPMs.

The last type is a hybrid. It's a 4 hole spacer at the carb but eventually tapers out into a open spacer. Kind of the best of both worlds.

"How much spacer should you use on your Chevy? As a rule of thumb, single-plane intake manifolds seem to respond best with larger spacers (2 inches in height and larger). On the other hand, most dual-plane intake manifolds work best with open spacers with a height of between 5/8-inch and 1 1/2 inches."


I pulled some facts off http://www.hotrod.com/techarticles/2944/index.html But most I recalled from various articles. The link has a wicked pic of the Moroso spacer which is a wedge type for people that use them on the strips and lift the front end off the ground

All spacers are is a bandaid for intakes or carbs that are too large or small for the motor. a fairly minor bandaid, but they never hurt and can be better than nothing. Which one to use of course depends on exactly what your mismatch is.

4 holers are meant to increase charge velocity, which is a problem both with a carb thats too big and an intake thats too big.

elongated 2 hole spacers are meant to increase plenum volume without ruining the split plenum effect that you get with a dual plane. Therefore best for use on a too small dual plane manifold.

Fully open spacers are for when you have a too small single plane, or too small a carb on either manifold.

:hail: :hail: :hail:

I forgot to add in the Demon Carb. book they say spacers can effect the rpm range of your powerband too.

I'm planning on putting a 4 hole on my Victor Jr cause I was afraid my 210 RR AFR heads won't give off enough signal to the 750 DP demon.

Jester i was about to post when i saw yours. I couldnt have put it better myself. If you buy the right stuff in the first place youll never need or want a spacer.

Just in case any of you want to know the purpose of a carb spacer, it's to increase bottom end torque, which was my original question.

Tuning aid more than a bandaid..

they are not specifically for boosting low end torque, some spacers depending on their configuration will boost low end torque, some will build high end horsepower.. etc and so on. There are very few absolutes in hotrodding there barry.

It is a rare occasion that a manifold and carb combination is going to be spot on for a given motor and vehicle combo. Especially considering that most manifolds are cast with less plenum than your average hot 350 needs simply because its easier to add a spacer than it is to remove metal from an intake manifold should it not fit under your hood or say you have a combination that doesnt need all that plenum.

You're right about the tuning aid, Pablo, but the fact remains that lengthen the distance between the carburator and the intake increases bottom-end torque....period. Look at the TPI system. From the factory, these motors have good bottom-end punch, due to the length of the "runners" or tubes that go from the plenum to the intake. That's why the power goes away at about 4500 RPM. Shortening those tubes moves that power to the upper power band (top end).
As for very few absolutes in hot rodding, or more accurately, engine-building, there are literally TONS of absolutes. "If you do x, y will happen." The problem comes from the fact that, in some cases, changing one thing affects other things, too. Everything is so "co-dependent". For example, if you put bigger jets in your carb, your heads may not be able to handle the flow, causing either poorer performance , or no gain. Or putting a ram-air set-up on your car. If your heads can't breath, it won't help. In my case, the heads, intake, cam. etc, can all handle more fuel, better mixed, with more air. Now all I have to do is get a REAL fuel pump on the car (next weekend-Edelbrock rebuildable...130GPH,13 PSI) and re-do pressure regulator, float levels, and carb jetting. As soon as I get all this sorted out, I'll be puttin' a 1" spacer on.(Because they're so cheap, and my air cleaner needs to be up in the air flow) Results will be posted. Whoever has this as their sig, I take my hat off to (I think it's Jim85iroc) "Weekend projects aren't..........":hail:

im going to disagree with you barry, i think you are getting plenum and runner confused.

Long tpi runners utilize resonance tuning, which i believe is called the hemholtz effect. The length of the runner plays a large part in where in the rpm band that resonance tuning takes effect the strongest, your cam, heads, etc should also be set up to take advantage of it as in a TPI setup things work together to give it alot of low end grunt because cam, heads, work to use the strongest resonance wave to the engines advantage.

Plenums are like capacitors for these runners, a ready reserve of air ready to fill the void that will exist when the intake valve opens. The smaller the plenum the stronger the individual pulses are to your throttle body or carburetor. This is why if you put a huge plenum or open spacer under an allready big carb youll have terrible low end performance since carburetors work on vacuum signal. That signal is dampened by the capacitor or plenum. If you didnt have boosters to worry about and say you had FI youd probably have no problem with low end torque youd just need to add alot more AE fuel to sort of play catch up for all that air in the manifold. Not to mention that in a big plenum you are probably alot closer to atmospheric pressure all other things being equal at WOT than a small plenum motor. This causes fuel suspended to condense and just collect on the manifold floor and walls (when there is a change )

a 4 hole spacer boosts the responsiveness of an engine because it has the effect of lengthening the runner that is your carburetor barrel. Giving the booster a much better signal because the velocity through the carb is increased. Bernoullis principle at work

Plenum..............runners..........don't have either one. I'm not a TPI kinda guy. Feel free to disagree. (I hope after reading this no one thinks I'm a rapper) That's what this org. is all about. Different points of view, and different experiences.

carb manifolds have plenums and runners too, that central area under your carb where there is a big open space or two seperate open spaces (dual plane) is the plenum, the passages to the cyl head ports and indeed the ports themselves are runners.

My manifold is a single plane. The spacer (1") is in and I think I have the fuel problem sorted out. As soon as I get the correct fuel pressure regulator installed, I'll know for sure, but it looks like the car has better throttle responce in the lower RPM range. I also have room for another 1" spacer.(3" cowl hood) Since they're so cheap, I may give it a shot. (See my post under carbutators for the continuing saga of my fuel system problems, but I got it fixed! As soon as my new fuel pressure regulator get here...2 days. If anyone cares.......)

Pablo with your explanation you've helped quite a bit of people who might be wondering about adding a spacer to their setup.

I got a 4 hole phenolic spacer for my carter AFB with single plane intake. I saw the same HotRod article, and was wondering if it would be safe to wedge my spacer and blend the holes with a dremel or something. I'm not too familiar with how well phenolic material holds up, so I don't want to scrap a $30 spacer...

phenolic has a similar consistency to wood but whatever you do, do not breath in the dust created by working with it unless you dont value your health.

The purpose of the spacer is to increase the velocity of the air and fuel being vacuumed, and to provide your cylinders with cooler more oxyginated atomization. Stronger vacuum means better atomization of fuel. A mix of fuel and air means a better combustion which constitutes in more power. High powerband intake manifolds with single plane holes have less vaccum at low rpm when you put a 4 hole spacer on a single plane intake it will increase lowend power and torque. Plastic spacers limit the conduction of heat to the carb, carb will boil the gas in the bowls. A cooler atomization of fuel and air will constitute more power and better combustion. Colder air is denser than warm air which has more oxygen, Mix that with gas it will give you a stronger explosion in the combustion chamber.

I cant talk the theory of induction much but from first hand observation
of numerous dyno pulls on a superflo 902 of various engines mostly small block chevys
I have noticed that 4 hole spacers in general broaden the torque curve some on the low end over single hole spacers or no spacers of about 200 rpm. losing a few h.p.
on the top end but with little or no torque loss. these pulls were made after
the engines had already been sorted out (fuel mixture, timing,ect) without any spacers to start with then just add the spacers with no tweaking in between. there has been a response gain also every time this has been done no matter how tight the tune was to start with
thats been my experience for what its worth

(Just saw how old this was! Info about spacers still valid)

My two cents...

I think spacers act differently depending on how the throttle blades are positioned. At part throttle (where we spend 90% of the time), the air mixture is directed where? How can you help the mixture make the turn into the runners in a more efficient manner? Keep these tow things in mind when porting spacers and intakes.

Secondly, If Barry's combo is the one in his sig and he has a high rise single plane, small cam, and probaly low compression, he is going to need more help than just fuel pressure to get the most out of that combo. A Victor Jr. on my 350 (ported AFR's, 240@.50 roller and 10.8:1 compression) killed my 1/4 mile times. Various open spacers on my air gap did the same thing. The magic combo was ported Air Gap and tapered spacer (I made it myself). It increased my part throttle response and vacuum went up about 2". It ran the same 1/4 times as no spacer on the ported air gap.

my dad an i built a 300hpwr 350 in my chevele with a stock intake an a chevy 4b qj ,,my problem was jets to small se we bumped up the jets by two numbers then stock,, then it was to much fuel,, so we then put on a 1 inch spacer,(4 hole plastic) then we adjusted the qj linkage so when the primearies where 1/4 open the seconders where open an 1/8... to even help it get a little better mix we put a hose on the stock air cleaner an whent strait through the radiator support for strait open air flow,( 2 INCH TO 3 HOSE from one of the hoses my dad had off one of his old peterbilts),, the increase in power from air fuel mix was 30%..my gas miilage was also better just not on the trak.. SO SPACERS DO THERE JOB... but thats just my story with spacers. sorry spell check don't work lol...

Ok Guys, PLEASE forgive me in advance if I miss protocol somehow. it's my 1st participation in forums, ever.

You ever have a friend that has a problem but doesn't want to accept help? My friend was sold a new high rise manifold and 600CFM 4 barrel by & from Edelbrock for his new crate - 40 over - 289 for a '66 mustang automatic with 2.5" headers and exhaust. He's been complaining about hesitation/bogging coming off idle or passing or I guess more than small accelerator movements in general. Says he's checked everything possible fitting and connection wise. I just learned from him a year later it's been this way since day-one. I'm disabled, live a ways away and have not seen/felt the car for myself. All the formulas I can find on the web, which seem to be nearly identical, conclude the carb's too big by about 100cfm. I'm not sure his ego will allow for accepting this even though the sales person at Edlebrock should have known better.

I may sound real stupid now - Can it be demonstrated/smaller cfm imitated/ by covering a portion of the top of the bores with duct tape or something to reduce input volume/increase velocity?

I replied to your post Jester because what you've said about spacers makes a lot of sense to me. Do you think this problem could this be "Band-aided" with the right spacer? Enough to maybe convince him to swallow his ego and bite the bullet [$ wise] and change things out? Or maybe it works well it can be left alone
THANKS in ADVANCE, Waterboy

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Welcome to the boards. This site is for 3rd gen f-bodies only. I'd recommend editting your post to make it more general.

That being said when I had bogging off idle and hesitation with my old Speed Demon I found it to be the accelerator pump arms were bottoming out. It would actually stumble hard enough it would stall the motor out. I readjusted them and that fixed that issue. I assume Edelbrock carbs also would have similiar things with their pump arms.

H20 - you should join Mustangforums.com and make a tech post there. That way if you have any other questions mustang related you can ask them without having your post removed as this is a third generation Camaro forum. I'm also on the Mustangforums, so you'll see my posts there as well. FWIW - that carb is definitely not too big for that motor. I'd say it's just right. If he's skilled with a carburetor (assuming he's done everything in his power to adjust/make changes as well as check everything else outside of just the carburetor) - he's probably going to need to tear it apart and see what's going on inside. It could be a host of reasons.