The V8 Owners Forum -

what spacer should i go for, i have a dual plane manifold bt don't know wether to go for a carb spacer with 4 holes or 1 big one?

I have a Eddy dual plain manifold but a spacer with one large hole, it seems fine. In fact in one of my books it states that you can cut the divider down on a dual plain manifold to allow each cylinder to breath through all four barrels of the carb without suffering the charge robbing effects that you can get on a single plain manifold.

Having said that I've heard a few people say that a spacer with one larger hole messed up their carburation so who knows what is right!

My mate has a SBC and the Eddy air gap manifold has the divider partially cut down straight out of the box.

I've tried both (made them myself), on a dual plane peformer RPM manifold with the edelbrock carb, I found the type with 4 holes seemed to work better.

The 4 hole type will work better if the carb has vac secondaries.

ok, thanks for help, looks like i need a 4 hole spacer,

Hello. I followed a link to this forum from another one discussing specs for racing lubricants, and noticed this thread. I thought I’d post a picture or two of a product that we designed a few years ago that has proven its worth quite successfully here in the USA.


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When used on the Edelbrock Performer (or other dual plane intakes with a fully divided plenum), this design allows each cylinder complete access to all four carburetor throttle bores, and also greatly reduces the plenum turbulence normally present in a dual plane manifold/conventional "open" spacer combination due to the air/fuel charge being pulled back and forth across the 90 degree edges at the top of the divider.

While simply lowering and radiusing the divider (or removing it completely) also gives each intake runner increased access to the carburetor's full airflow capacity...and that alone often results in a net increase in performance...such modification also allows each intake runner to more easily "rob" pressure (as well as kinetic energy in the form of column inertia) from it's brothers on the opposite side of the plenum…energy that you had already "bought and paid for" on those cylinders' previous intake events. The cylinder filling (and therefore torque production) lost to this waste of kinetic energy can be substantial even at “road” RPM levels.

If you have room under the bonnet for it, this spacer design has proven to be an efficient solution to each of these concerns.

Self edit: Apologies Mods; I didn't read the site rules pertaining to vendor offerings until a few moments ago. Hopefully, my edits to this post will bring it into compliance with both their letter and spirit.

StanJ66 wrote:
While simply lowering and radiusing the divider (or removing it completely) also gives each intake runner increased access to the carburetor's full airflow capacity...and that alone often results in a net increase in performance...such modification also allows each intake runner to more easily "rob" pressure (as well as kinetic energy in the form of column inertia) from it's brothers on the opposite side of the plenum…energy that you had already "bought and paid for" on those cylinders' previous intake events. The cylinder filling (and therefore torque production) lost to this waste of kinetic energy can be substantial even at “road” RPM levels.

If you have room under the bonnet for it, this spacer design has proven to be an efficient solution to each of these concerns.

Self edit: Apologies Mods; I didn't read the site rules pertaining to vendor offerings until a few moments ago. Hopefully, my edits to this post will bring it into compliance with both their letter and spirit.

That's what I said a few posts earlier in this thread! (sort of!)

Shiny bits like that always look great lol

StanJ66 wrote:Hello. I followed a link to this forum from another one discussing specs for racing lubricants, and noticed this thread. I thought I’d post a picture or two of a product that we designed a few years ago that has proven its worth quite successfully here in the USA.
When used on the Edelbrock Performer (or other dual plane intakes with a fully divided plenum), this design allows each cylinder complete access to all four carburetor throttle bores, and also greatly reduces the plenum turbulence normally present in a dual plane manifold/conventional "open" spacer combination due to the air/fuel charge being pulled back and forth across the 90 degree edges at the top of the divider.

While simply lowering and radiusing the divider (or removing it completely) also gives each intake runner increased access to the carburetor's full airflow capacity...and that alone often results in a net increase in performance...such modification also allows each intake runner to more easily "rob" pressure (as well as kinetic energy in the form of column inertia) from it's brothers on the opposite side of the plenum…energy that you had already "bought and paid for" on those cylinders' previous intake events. The cylinder filling (and therefore torque production) lost to this waste of kinetic energy can be substantial even at “road” RPM levels.

If you have room under the bonnet for it, this spacer design has proven to be an efficient solution to each of these concerns.

Self edit: Apologies Mods; I didn't read the site rules pertaining to vendor offerings until a few moments ago. Hopefully, my edits to this post will bring it into compliance with both their letter and spirit.

What does this do for fuel economy when used in conjunction with the dual port (Not dual plane) manifold?

Richard P6 wrote: What does this do for fuel economy when used in conjunction with the dual port (Not dual plane) manifold?

I'm not sure that it would work too well with a dual port manifold because the dual port is meant to keep the primary venturies separate from the secondary venturies. I believe it does this do keep the gas speed up at small throttle openings.

Of course I could be wrong about all of the above!

sidecar wrote:

Richard P6 wrote: What does this do for fuel economy when used in conjunction with the dual port (Not dual plane) manifold?

I'm not sure that it would work too well with a dual port manifold because the dual port is meant to keep the primary venturies separate from the secondary venturies. I believe it does this do keep the gas speed up at small throttle openings.

Agreed...at least to the extent that this particular spacer design would tend to soften the vacuum signal presented to the primary venturis at part throttle. A dedicated design for use with a dual port manifold would be a different animal altogether.

It's a shame that the dual port intake manifold design never really became popular here on this side of the pond. I suspect the reason has much to do with the cheap gas prices we've enjoyed. The various Offenhauser iterations of the concept which were offered here during the mid '70's to mid 80's worked quite well on the street. I've kicked around the idea of designing a complete package (true "split port" cylinder heads, intake manifold, carb and camshaft) around this concept over the years; might be an idea whose time has finally come.

will this be suitable?

http://cgi.ebay.co.uk/2-Phenolic-Carb-s ... 33426da680

Yes provided you stick a radius on the bottom side of each of the holes in the spacer equivilent to 1/4 of the bore diamiter otherwise it is equivilent to reducing the bore diamiter by about 8%.
Best regards
Mike

so they just need opening up a bit then?

no, they don't need opening up, just a radius on the bottom of each hole, like a bell mouth.
Like this one is radiused http://www.summitracing.com/parts/WSN-024110/
Mike