old timer intake trick?

[wazazzle]

i heard an old timer trick to get the best of both worlds dual & single plane advantage was to take about 1" from the top of the plenum divider. don't really believe this but is this true? i was thinking of going with an old holly dominator single, but if i can p/u an dual modify as above i was going to do that if it works. thanks

 

[302 coupe]

I wouldn't do it. If it worked, everybody would be doing it.....

 

[mfp4073]

if it worked as well as claimed, why would they not make them that way. You better believe that the intake companies have tested it.

 

[65myway]

Actually, if you look at a picture of the Edelbrock Air-Gap intake, it looks like this. Of course, it looks as if only about 1/2" is removed from the divider, but it is being done on aftermarket intakes.

 

[4MuscleMachines]

Thats correct, Air-Gap intakes have about 1/2 inch removed from the top of the plenum divider.

 

[tos]

This mod was done by engineers using alot of calculations and test equipment and maybe even an abicus (D.Hearne will get me for my spelling) so i wouldnt risk it on a known good intake Unless you had exact measurements and the proper tooling. Intakes arent real expensive so I would suggest buying one already done.

 

[bnickel]

it's really not that scientific, the main reason that some intakes are like that is to help equalize flow between the two plenums, for the most part it really only works at higher rpms.

i beleive this mod was discovered accidentally when holley started making the 3 barrell carb and the intakes had to be modified to work the huge secondary butterfly.

if you do the mod it does not have be that scientific just cut out a notch about 1/2" to 3/4" deep. i would recommend that you actually cut the piece out as opposed to grinding it out, that way you could have the piece welded back in if you aren't happy with the results.

 

[krash kendall]

Why not just put in a non-divided carb spacer? BTW- My 1" edelbrock spacer is divided to match the manifold.

 

[tos]

How about a carb spacer, If you have the room under your hood that is. There only a few bucks at your local parts house and they have different variaties that I think will accomplish the same thing your going for. You can buy one opened in the center or hack one up how ever you like without loosing much money or time if it doesnt work.

 

[wazazzle]

think i'm gonna go with the open spacer and dual plane intake. thanks guys

 

[brianj5600]

Parts are modified all the time even though they are well engineered. There are companies like TEA that stay VERY busy improving well engineered parts. I doubt you will be able to feel a difference one way or the other. I think it will fepend on if your cam is too big for the intake.

 

[Vinyl66]

I ground the divider down some on my standard RPM intake to mimmick the RPM air gap intake. Did it work? I don't know. You would have to do back to back testing to know for sure. I figured it would help because the RPM air gap is a newer design and I don't think Edelbrock would do something to purposefully hurt horsepower.
An open carb spacer will do the same thing. Carb spacers seem to be a crap shoot. What works for one combination may not work for another. From what I have seen, a 1" heat insulating spacer (plastic, wood) usually seems to help. Open or 4 hole seems to be the crap shoot. I think I have seen more open spacers on dual planes because of the reasoning above and more 4 holes on single planes to give the carb booster a stronger signal.

 

[2nd Mustang]

A little off the topic, but I took an old Holley 600 and cut off the airhorn over the primaries and removed the check ball in the vacuum secondary housing. Wow, the low end power really picked up! Just too much for street driving so put on a regular 600 again.

 

[rbohm]

cutting the plenum divider can help make power, as bnickle stated mostly in the upper rpm ranges, but it can also lose power as well. it depends on your combination, and what rpm range you are running in. the reason some builders modify the plenum divider is because a normal dual plane isnt enough, and a single plane is too much intake. but you need to dyno test the car to see if it helps or hurts at all. also any gains you see are normally going to be some what small overall, 5-10hp at best, so dont expect too much.

 

[bnickel]

it's also especialy helpful if you have one bank running leaner than the other, as it will help even the mixture out. if you both banks are already running fairly equal you probably won't see much of a gain in HP but it will likely make some. but rbohm is right it could hurt performance as well.