Open spacer on a 427 Dual quad MR intake?

[427LX]

How well does an open type carb spacer work on the intake manifolds with 4 hole plenums?
Should you stay with 4 hole spacers only?

[Posi67]

Logic would say that a 4 hole spacer would work better than going from 4 holes in the carb, to an open then back to 4 holes however I have nothing to back this up. So far, I haven't tried anything other than the Super Sucker style spacer which is kind of between them both on my 390. I think I'll swap that out for an open and test it which may help figure out why it's so slow...   

[jayb]

Based on the testing I did for my intake manifold book, there really is no general rule of thumb that will tell you which spacer is best.  However, I have tested open spacers with four hole intakes, and not seen any improvement in top end power, while often seeing a decrease in the torque peak.  Unless you have the opportunity to test on the dyno or at the track, where a back to back comparison could be performed, I would probably stick with the four hole spacers on a four hole intake.

[Posi67]

On the opposite side, I never found any difference running a four hole spacer into the T-Wedge plenum intake so stuck with the 1" open on that setup. My junk is hardly a quality test piece and would think some back to back Dyno pulls would be the best way to get a feel for what works. That may or may not translate into better ET's but at least the Data would be valid.   

[blykins]

I'm a Super Sucker fan.  They're even making them now that have an undercut under the middle for dual plane intakes. 

But to echo all the other guys, try it and see.  That's about the only way you'll find out.  I've seen spacers not add one horsepower and on two occasions, I've seen a spacer add about 30 hp. 

[427LX]

Well I came up with this today and it did make an improvement...definitely pulls harder thru the gears and didn't seem to loose any low end.
A one inch open spacer on top of my hand crafted 1/2 inch phenolic which helps give a smoother air entry to the 4 plenum holes. All this times two of course on my 427 Windsor.  Other setup was a 1.5 inch 4 hole spacer under each 600 Holley.

[Posi67]

Now there's some clever thinking.. Certainly looks like it would work well and reduce any inversion due to the mismatch. Nice job.

[427LX]

Got that idea last night and it is like what a tunnel ram runner entry would be like inside the plenum!
Some of you guys might want to give it a try. May try a 1.5 inch tall open spacer at some point and see what happens.

[Joe-JDC]

Been doing that for years.  Will be dyno testing a similar setup soon.  I use many different spacers with the openings cut with a radius for all my intake manifold testing.  I have also used the spacer turned over on dyno testing on other type of engines.  I use a router and either 1/4" half round, or 1/2" half round to give me the radius I need on phenolic, plastic, bakelite, or aluminum.  If you go slowly and backwards with the router it is not as aggressive and makes a very nice radius.  I even do that to  Cobra/427/Thunderbird air cleaner bases to aid the turning of air into the carburetors.  Joe-JDC