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 Post subject: Intake manifold porting...
PostPosted: Sat Aug 24, 2013 11:53 am 
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Joined: Sun Dec 26, 2010 11:42 am
Posts: 519
Location: Florida
From what I have read, Gessler is no longer doing this service. Their web site says, "After 25 years of porting Cylinder Heads, Intake and Exhaust Manifolds. We are taking a break. We are not accepting any new porting work."

Does anyone have another source for this kind of specialty work? I myself do not have a bridgeport mill, and have zero interest in trying to remove material by hand with a die grinder.

I have read a lot of negative reviews about extrude hone on intakes and exhaust manifolds. (Not to mention they want an arm, leg, and your first born for their services)

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 Post subject: Re: Intake manifold porting...
PostPosted: Sat Aug 24, 2013 11:35 pm 
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Joined: Fri Jul 25, 2008 6:12 pm
Posts: 2462
Location: North Salem NY
Any machine shop could easily open you plenum for very little cost!

For the scope of your build, i would open up by utting maybe a half inch down on the divider andin the middle go anothee 1/2" betweenthe primarys and secondaries!

I would say thats a good start!

I would leave the runners alone! Your heads will be the most bang for your buck!

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 Post subject: Re: Intake manifold porting...
PostPosted: Sat Aug 24, 2013 11:50 pm 
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Joined: Sun Dec 26, 2010 11:42 am
Posts: 519
Location: Florida
Thanks Ted, I would be working with a factory cast iron "boat anchor." I figure I need to modify it to look something like this...

Image

Image

Here is an Olds intake, but it has a similar carb flange as my intake. The modifications would take it from this:

Image

To this:

Image


Head work is of highest priority, just want to make sure I have an intake manifold able to somewhat feed it.

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 Post subject: Re: Intake manifold porting...
PostPosted: Sun Aug 25, 2013 9:20 am 
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Joined: Fri Jul 25, 2008 6:12 pm
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Location: North Salem NY
I would do it like the second picture!

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 Post subject: Re: Intake manifold porting...
PostPosted: Sun Aug 25, 2013 9:31 am 
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Location: Florida
I know it has been a practice for years, but I have never understood the concept of cutting down the center divider in a dual plane intake. Looks like I will spend some time today searching that topic...

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 Post subject: Re: Intake manifold porting...
PostPosted: Sun Aug 25, 2013 10:10 am 
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Joined: Sun Dec 26, 2010 11:42 am
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Location: Florida
Quote:
“On some of our dual-plane manifolds, we will cut down the center divider; it varies from one manifold design to another,” explains Smith. “The amount that the divider is cut down isn’t determined by numbers on a dart board. This is all based on dyno testing and flow testing by our engineers. What this does is help balance the air signal to the carburetor for the air/fuel mixture at higher rpm. This technology goes back as far as Vic Edelbrock, Sr, and the old slingshot manifolds on flatheads."


By this statement, if I understand correctly, cutting down the divider is more beneficial for an engine that sees higher RPMs. (what I am planning to build most likely will be done by 5000 RPM)

Quote:
when the GM engineers drastically altered the L-72 intake for the L-88 then ended up stagger jetting the carb, and adding "air flow tabs" to keep all the cylinders balanced. How many guys removed the divider without checking cylinder exhaust temps for lean cylinders? Or modifying the carb to compensate? See my point.

When in doubt, stick with the factory configurations


Good point here, I never knew about the "air tabs."

Quote:
As stated, cutting down the plenum divider makes the manifold act more like a single plane manifold than a dual plane manifold. A dual plane (180 degree) takes advantage of some favorable wave dynamics at low revs to enhance low end torque and provides a better fuel metering signal to the carb. The carb will usually require richer jetting to maintain desired fuel-air ratio if the divider is cut or a single plane manifold is substituted for a dual plane. Chevrolet recommends specific "stagger jetting" (different sizes at each corner) for big blocks with cut down center dividers

A single plane manifold or cutting the divider down on a dual plane will increase top end power (assuming the carb calibration is modified to maintain proper fuel-air ratio), but at the expense of low end torque since the favorable low speed wave dynamics are reduced or completely lost.


This quote is directly from Cliff Ruggles, in a discussion about a QJet-specific application. He went on to say how his personal car lost power and ran slower with spacers. (4 hole and open)

Quote:
Use extreme caution with any modifications to the divider. We have recorded some significant LOSSES in power taking out the divider or even modifying them. A small notch or divit between the secondary throttle plates is fine, or use an open gasket.


That's it for now, but thought I would share what I found with a quick search.

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 Post subject: Re: Intake manifold porting...
PostPosted: Sun Aug 25, 2013 2:42 pm 
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Location: North Salem NY
I agree with parts of that and its fine to stick with stock config if your stock and or not spinning high rpms, but a 500 incher likes to draw more and opening up helps, the booster signal is somewhat protected by leaving some of the divider! Its definatly car specific!

Thinking about it, if your not spinning it to high and running a stick and want street manners, i would leave the divider until you think to yourself hey i need more hp!
Then try it with an open spacer before

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 Post subject: Re: Intake manifold porting...
PostPosted: Wed Aug 28, 2013 7:53 pm 
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Joined: Wed Dec 29, 2010 2:17 pm
Posts: 22
Location: PLYMOUTH MEETING, PA
1972LS5Chevelle wrote:
From what I have read, Gessler is no longer doing this service. Their web site says, "After 25 years of porting Cylinder Heads, Intake and Exhaust Manifolds. We are taking a break. We are not accepting any new porting work."

Does anyone have another source for this kind of specialty work? I myself do not have a bridgeport mill, and have zero interest in trying to remove material by hand with a die grinder.

I have read a lot of negative reviews about extrude hone on intakes and exhaust manifolds. (Not to mention they want an arm, leg, and your first born for their services)



May be a little costly, but I have used Dr J in California on several builds for myself and customers :aok Google Dr J or airwolf heads and you should be good. Bryce is a nice guy and usually answers his own phone. He was a bit behind with all the Yellow Bullet National event stuff for this weekend that he had to get done, but he should be getting caught up soon. You will not be disappointed and the wait is worth it. :bow


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 Post subject: Re: Intake manifold porting...
PostPosted: Wed Aug 28, 2013 8:38 pm 
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Joined: Sun Dec 26, 2010 11:42 am
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Location: Florida
I was under the impression he only did aluminium heads and intakes? I guess he does cast iron too?

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 Post subject: Re: Intake manifold porting...
PostPosted: Wed Aug 28, 2013 9:32 pm 
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Joined: Fri Jul 25, 2008 12:26 am
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Location: Bristol CT
I thought you were building a pure stock? If so no mods allowed to the intake.

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70 RoadRunner 440+6 Auto 11.21 @ 124MPH 1.72 60' S/A

70 RoadRunner Hemi Auto 12.39 @ 113MPH 1.90 60' S/A

71 GTX 440+6 Auto 11.35 @ 123MPH 1.79 60' S/A

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 Post subject: Re: Intake manifold porting...
PostPosted: Wed Aug 28, 2013 10:04 pm 
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Joined: Sun Dec 26, 2010 11:42 am
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Location: Florida
I am, different engine for a different car.

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 Post subject: Re: Intake manifold porting...
PostPosted: Thu Aug 29, 2013 8:20 am 
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Joined: Fri Jul 25, 2008 12:26 am
Posts: 6803
Location: Bristol CT
1972LS5Chevelle wrote:
I am, different engine for a different car.



Got It :aok

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SUPERCAR LEGAL

66 Belvedere I HP2 Hemi Auto 11.13 @ 124MPH 1.68 60' S/A

70 RoadRunner 440+6 Auto 11.21 @ 124MPH 1.72 60' S/A

70 RoadRunner Hemi Auto 12.39 @ 113MPH 1.90 60' S/A

71 GTX 440+6 Auto 11.35 @ 123MPH 1.79 60' S/A

71 RoadRunner 440+6 4Spd 13.61 @ 101MPH 1.99 60' P/S

72 Demon GSS 340 S/A 11.81 @ 118MPH 1.91 60' S/A


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 Post subject: Re: Intake manifold porting...
PostPosted: Wed Nov 12, 2014 4:10 pm 
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Joined: Tue Oct 19, 2010 5:29 pm
Posts: 96
Location: CT
Thought I would share some experience in regards to this topic.I will start off by saying removing the plenum divider on a GM 163 high rise was worth 40 flywheel HP on 496 platform using stock 291 heads with no other changes.
With that in mind,I wanted to put the stock LS6 low rise back on my car.I didn't want to modify a GM intake,so I picked a repro and spent $75 at the local machine shop and had the divider milled down to the recommended .090 tall lip.
Testing at the track revealed a new best ET on Polyglas tires with the swap...a 12.72 vs. a previous best of 12.81 with an Edelbrock RPM intake.The 12.72 was in a headwind too.No jetting changes either.Still the same config as when I had the RPM intake.

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1970 SS454 LS6
11.99 @ 110 MPH,1.69 60 ft. w/3.31 gears (on Hoosier QT Pro tires)
12.57 @ 110.6 MPH,2.03 60 ft. (on Goodyear Polyglas)


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 Post subject: Re: Intake manifold porting...
PostPosted: Wed Nov 19, 2014 7:46 am 
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Joined: Tue Oct 19, 2010 5:29 pm
Posts: 96
Location: CT
Here is a pic of my intake:
Image

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1970 SS454 LS6
11.99 @ 110 MPH,1.69 60 ft. w/3.31 gears (on Hoosier QT Pro tires)
12.57 @ 110.6 MPH,2.03 60 ft. (on Goodyear Polyglas)


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