carburetor spacer

[dan miller]

It's my understanding that a carburetor spacer increases peak power by about 500 rpm for each inch of height. Probably an EMC loser. However, it's also my understanding that a carburetor spacer increases torque across the board. An EMC winner.

It never occurred to us to not utilize a spacer, and all (as far as I recall) EMC engines had spacers.

Is there anything here to waste any brain cells or energy thinking about?

Thanks, Danny

[stealth]

Kettle of worms there my friend…….

Get yourself a few adult beverages a bag of snacks type in carb spacer into the search and you'll have an entire evening of reading.

mike

[randy331]

It's my understanding that a carburetor spacer increases peak power by about 500 rpm for each inch of height.

Have you added a 1" open spacer, and netted a 500rpm increase for peak HP?
I would think for this to happen, the engine would have to be badly starved for plenum volume. For the point an engine makes peak power at to go up 500rpm, the rpm at which peak ve is at, would also have go up close to that 500 rpm. I don't see a 1" spacer doing that.
I ran a 2" open, a 1" open, and a 4 hole super sucker on the dyno on a mild 355' engine. There was no significant diiference in the amount of peak power, or the rpm it made it at. The super sucker picked up a few lbs. of TQ below peak TQ, but no difference from that point up.

Randy

[Doug Schriefer]

Carburetor Spacers:

Carburetors spacers can be a very useful tuning aid when working on your streetcar, or racecar. A spacer can be used to move the torque and power-band where it is more usable in your application, or they can be used to help work out inefficiencies in your combination.

4-Hole Spacers. As a rule of thumb a 4-hole designed spacer (4 individual holes one under each barrel of your carburetor) will increase your throttle response, and acceleration. They can also move the torque and power-band down in the RPM range. This is accomplished by keeping the air and fuel flowing in more of a column, which increases the air velocity. This can be a perfect addition if your vehicles throttle response is not as good as you’d like, or you’re getting passed when you pick up the throttle coming off of the corning. A 4-hole spacer can also help make up for something in the intake tract being larger than optimal (too large of a carburetor, cam, intake, etc.)

Open Spacers. As a rule of thumb an open designed spacer (1 big hole underneath your carburetor) will decrease your throttle response, and acceleration. They can also move the torque and power-band up in the RPM range. This is accomplished by increasing the plenum area, which will help in the higher RPM’s. This can be a perfect addition if your vehicle has traction problems when accelerating, or coming off of the corner. A 4-hole spacer can also help make up for something in the intake tract being smaller than optimal (too small of a carburetor, cam, intake, etc.)

Combination Spacers. A combination spacer (half 4-hole, and half open) can give you the best of both worlds. Increasing your throttle response, and acceleration over not using a spacer, and increasing or broadening the torque and power-band.

Plenum Dividers. A Plenum divider does as the name implies divides the plenum in an open plenum intake manifold from side to side. These are generally used to help prevent fuel slosh from side to side in high G load Oval-Track, or Road-Race applications. It is common on certain engines to have lean cylinders do to fuel slosh. A SBC oval track engine running on methanol can run lean on cylinders 3 & 5 while cylinders 4 & 6 will run rich. A plenum divider can help eliminate this.

Spacer thickness. Varying the thickness of your spacer will affect how it affects your engine. Normally the thicker the spacer the more of an affect if will have on your combination. Meaning if a ½” thick spacer helps you a little a 2” thick spacer can give you more of the same affect.

Spacer Material. There are many different types of materials used for manufacturing spacers. They all have pro’s and con’s. Wood for example is a great material as far as thermo efficiency, but can wick fuel, which is not safe. Plastic, or composite spacers are also very good at not transferring heat, but are not as strong, and can be harder to modify. Generally Phenolic fiber, or Aluminum is preferred. Phenolic is very good at not transferring heat, but can be hard to modify. Aluminum is not as good at heat dissipation, but can be ported or modified easily to work on specific applications.

Spacer Tuning. Since each spacer will react differently on each combination there is not a right or wrong type. Spacers are a great tool to have to help dial in a new combination, or tune your racecar for varying track conditions. Swapping out a spacer is a very simple change that can have great impact on the drivability of your streetcar, or racecar. Having a couple types, and thickness of spacers around is always a good investment.

[bigjoe1]

I have been doing the spacer thing since 1965 now, I have never seen it do too much, It might make 10 more peak HP at 100 or 200 differant than with out the spacer, Some engines do NOT respond at all, or they DONT like it at all. There is no for sure gains here. Most of the time, you will find something like 5 to 10 HP, that all.

JOE SHERMAN RACING ENGINES

[racecar100]

I think doug has it peged to a T, Bill Jenkens referd to items that don't
realy show much on the dyno but the driver can tell there is something
there, as driveabilty.

[Troy Patterson]

Also, you've got to consider that when you change the type of spacer or add or remove a spacer you are also altering the metering signal to the carburetor and therefore the fuel curve.

Accordingly, the carbs tune or calibration needs to be adjusted otherwise a beneficial change - which ever that might be - may not be realized.

Troy Patterson TMPCarbs.net TMP Carbs

[dan miller]

Thanks All

I really appreciate the input. We have zero, and I mean ZERO experience with either carburetors or gasoline. I rejetted the borrowed 4150 back to stock Holley jet sizes and we ran it. We did not change any air bleeds. Predictably, our AFR and BSFC numbers were way off.

We did try three 1" spacers (open, 4 hole, combination), and found the HVH Super Sucker combination spacer worth a horsepower or two. It never occurred to me to try a pull without a spacer.

I'm going to try to borrow a better carburetor this year and it is our intention to have Troy beat it into submission. I've also been reading all I can find on carburetors, so hopefully we'll have a better feel for what's going on.

This is a neat site. Hopefully there will come the time when a question is asked that we can offer advice on, rather than just asking question after question.

Thanks again, Danny