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Discussion Starter · #1 ·
I’m going to fix my leaking intake gasket, and I figured I would clean the ports up and also cut the divider down a little on my Holley 300-36. Suck squeeze bang blow gained about 5-10hp on a performer rpm, and with it cut, was equivalent in power to an air gap, so I figure why not do it to mine, since I’m always looking for that extra 1hp.

Would be it a good ideal to knife edge the divider and smooth it out after cutting some of it out.

Also what’s a good distance to go down on the divider?

Thanks

Aaron
 

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I would say yes in the knife edge.

The divider can be "tuned" to raise the power band, determined by how far you take it down. You can see what I am talking about on a BBC RPM as compared to a Weiand Stealth.

Normally it is 1/2"-3/4" down on the aftermarket intakes.
 

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If you have the hood clearance ,before doing that you should try adding and testing your combo separately with (BOTH) a 1"-0r 2" open center and 4 hole carb spacers under the carbs, as it will give a clearer indication of how your engine will respond to changes in the plenum design, and if it gets WORSE its a fair indicator that removing the current plenum divider will not help much, generally removing the current plenum divider will kill some low rpm torque and increase the peak hp but thats NOT always a good trade off,in your cars E.T./1/4 mile time slip

http://forum.grumpysperformance.com/viewtopic.php?f=55&t=1038&p=4014&hilit=spacer#p4014
 

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Discussion Starter · #5 ·
thanks guys. ill check out links and pics when i get home.

keep the info coming though.

i made 303whp with a 1" 4hole spacer, but my best et and trap 13077 @ 104 1.96 60' was with a 1" open.

i would like to cut the divider down when the intake is off, as it will help w few more hp, and i will knife edge/round the edges inside, and clean up all casting imperfections with a sanding roll.

im not sure if I have enough room for a 2" spacer, but i could try stacking my two on op each other to see if i do.

i also thought about filling the crevice of the 4 hole (the underside is open, they are both plastic ones) with epoxy, and reshaping the throttle bore holes, kind of like a high dollar Wilson to try. i mean at worse i lost 15 bucks.

thanks

aaron
 

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You can spend time inside the plenum to enlarge it by working/straightening the walls, transitions to the runners, etc.

This one I did awhile back is enough to support 548hp/480 tq on a 347 ford with a HR cam. Was done all the way through though
Some of the pros here can see theres still room for improvement; just a backyarder here. I dont know that notching did any good but thats what the guy wanted :eek:

The advice given above about trying different spacers first to see what the motor likes is good stuff;have a feeling a 1"open is the ticket but you never know.



 

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I have seen them taken down quite a bit further than this, some almost all the way to the "floor".

Grumpy, thanks for the link. I registered at your site, and that was a good read. Looks like a 4-hole 1" or 2" phenolic is in my build plans now, betyween the 2101 performer and my 600 holley. :yes:
 

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Discussion Starter · #8 ·
think its worth it on a 300-36 holley, with 180cc brodix heads and 231/239 voodoo hydraulic roller cam?

i dont want to loose too much tq, or anything else with porting.

aaron

edit. i registered, but am at work, so i cant get my activation code right now.
 

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i dont want to loose too much tq, or anything else with porting.
You wont, the runner length is still the same.

Had a 10:1 350 with a 280 mega cam, 300-36 Holley, etc.
With a 4 hole the lower end seemed to be a little more snappy but lost up top. It was explained to me the 4 hole I was using was causing the air/fuel at higher rpm to bounce off the floor of the plenum disrupting flow. Again Im no expert, food for thought.
 

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Discussion Starter · #11 ·
You wont, the runner length is still the same.

Had a 10:1 350 with a 280 mega cam, 300-36 Holley, etc.
With a 4 hole the lower end seemed to be a little more snappy but lost up top. It was explained to me the 4 hole I was using was causing the air/fuel at higher rpm to bounce off the floor of the plenum disrupting flow. Again Im no expert, food for thought.
interesting, but what about overall port velocity, wont it decrease?

Rounded is better than knife edge.... Just to echo what has been said...
well that just sums it up then.

so say i cut the divider, the lower portion of the divider, should those edges be rounded also?
and should the entire length of the divider be cut, or just the center section like the air gap?
and if so should the protruding edges be rounded also?

im thinking of rounding the corners at the carb flange to transition the side walls from the back walls (not the top of flange down into the port).

any other ideas?

thanks guys

aaron
 

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You should radius everything as well as you can, do not knife edge.

Look at the runner cross sections, if you do work at one place, you will need to open it all the way through to gain the volume and flow.

To be honest, if your looking to do that much work, you almost would be better going to a different intake that flows better.

Cut your center divider down if you have played with spacers and the open spacer gains power and street manners, and then concentrate on any sharp corners or turns in the runner, that is going to give the biggest gain for time spent.

-Bobby-
 

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Discussion Starter · #13 ·
origional plan was to cut the divider, and radius all sharp edges right there in the center, and if there is any slag, or not soo smooth spots, i planned on smoothing them out.

i am not trying to hog anything out, or change too much, just clean it up while its off.

thanks again guys.

aaron
 

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Without much data to back me up, I'd say keep the cut to 1.00" max. I had one of the oem manis we cut the center out of, you couldn't beleive the seat-of-the-pants gain when I put a divider back in, with about a .650" gap on top. Damn thing never rev'd up so quick! 180s need a bit of "signal separation" to work well, it seems. Therefore, no knife edge. Round is fine.
 

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Discussion Starter · #15 ·
thanks for the write up paul. i have tried both, and the open seems to run the best. but i only dyno'd the 4 hole. i will play with both.

67- nice work on that intake.

im going to cut the divider about .5-.75" down, and radius anything that could use it, clean some stuff up, and throw it back on. i figure i might as well do this as i have to repair the leaking china wall.

thanks again guys.

aaron
 

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I have had some thoughts in the past on the knife edge versus the round edge regarding air flow. I would think if the air was coming straight on into divider it might not make much difference. However if the air is coming in at an angle which is most likely as to what is happening there would be more shear with a knife edge versus a round edge. In others words the air would go around the round edge in a better fashion than it would with a knife edge. Less vortexes and better air flow with a round edge. Anyways just my thoughts on the subject good or bad. :)
 

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1989GTA is EVERYWHERE!! He is the gentleman who does all the great port work on our TPI
runners and intakes here in the OC!

Hope all is well with you.

Pat
 

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Drop the divider about an inch and radius the leading edge.....no knife edging for best results.

Hope this helps clarify what the leading opinion looked to be anyway.

:beers:

-Tony
 
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