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Discussion Starter · #1 ·
I'm thinking about a new intake manifold along with the other goodies I'm going to use for my next rebuild,hopefully early next year.What advantage or disadvantage is there to having an air gap versus a non air gap intake? I'm thinking about using one of the Edelbrock Performer RPM rectangular port models,I currently have the GM aluminum dual plane high rise # 3933163 model.Looking for opinions on this choice!!
 

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yeah man

this guy knows his stuff! the air gap has the gap under the plenums to make the intake air cooler, this in turns makes more power! but be warned that this is a high rise intake and may not clear your hood,and is good to 6500 rpm. this intake will ultimately make more power than the rpm............adam
 

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The air gap will keep your inlet temp denser when the engine has been running for some time. It wont heat soak as much.
But if you spend some cash on gettin´the old ported you will see a good performance gain there.
DoC
 

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Discussion Starter · #5 ·
RPM Performer or Air Gap???

Thanks for the replies,DoC how would I go about porting my original intake? The only thing I have heard about in regards to intake manifold's is to have them port matched,are you saying there is more that could be done?
 

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You knife edge the air seperators under the carb, and smooth everything out helping airflow, and you port match them to your new heads, and move accesive material in the runners, you can do this your self, and it will be 20$.
The port match is easiest if you put thin wet paint on the heads and put your manifold on, and when you take it off again you have a nice mark of where the head runner is on the manifold and you grind it of, and smooth everything out.
Ask if you need any more info.
DoC
 

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I´m not familiar withe the intake you have, but I can´t say for sure that the money on a new intake would be well spent.
Yes, the theory is that it will keep the air cooler and free up ponys. I´ve tried both kinds and can´t say it was worth the effort. Another thing about air gaps is that in cool weather the engine can be a bi**h when it´s cold. It´s keeping the air too cool
 

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Discussion Starter · #8 ·
RPM Performer or Air Gap???

Thanks for the replies.DoC by the seperator do you mean the divider under the carb?I was almost thinking about removing this alltogether.My new heads are supposed to be port matched to the proper gasket,would I be able to use the same gasket to port match the intake?
 

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Although I've been flamed for this before... just something that was observed by many independent tests.... Air gap intakes still heat up as much as non-gapped manifolds, it just takes longer. If you think about it, aluminum is an excellent conductor of heat with a high specific heat gravity. The heat just has to go a further distance (out the base and up the runners instead of straight into the runners).

Don't take my word for it, consult Car Craft, Hot Rod, Popular Hot Rodding, or use your own thermometer like I did. On the average, the runners on my Edelbrock 2101 reach 180 degrees in 14 minutes of highway driving. My Vortec Air gap performer takes about 30 minutes of highway driving to reach 180 degrees. That's using a digital laser IR thermometer averaging the temps of all 8 runners. Both have no exhaust crossover. The only difference I did notice was that on the Air Gap the end runners took considerably longer to heat up than the center runners.

In my opinion, the Air Gap should be used for its higher runners which tend to show more hp on the dyno over the non-gap intake, but don't mistake it for a cooler intake charge unless all of your trips are very short. :)
 

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Guy Hiltz said:
Thanks for the replies.DoC by the seperator do you mean the divider under the carb?I was almost thinking about removing this alltogether.My new heads are supposed to be port matched to the proper gasket,would I be able to use the same gasket to port match the intake?
Don´t. The plenuim wall was put there for a reason
 

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You can use the gasket as a skabelon, but i prefer to use the paint method to avoid nicking the gasket.
It is where the runners enter the plenum, you sharpen.
If you grind out the divider in the plenum you have a single plane mani, and unless you have a hi po motor you dont want that, and you will also need a
turtle in the plenum to split the airstream properly.
I have some pic of a ported manifold you can see, but it will have to wait untill tomorrow cuz my own internet is down :(
The performer rpm is a good manifold to 450 hp, but it is also 300$ + shipment, where your own port is cheaper, like 280$ cheaper, and is good experience and it is cool to have ported it your self.
DoC
 

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I have to agree with curtis73 on this about the Air Gap Manifold. I think it is more of a marketing ploy than anything else.
 

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Discussion Starter · #15 ·
RPM Performer or Air Gap???

Thanks for all the replies,its much appreciated!From what I've read here I dont think an Air Gap is in my future,but I might see if I can do a little work on my own intake.DoC if you can post some pictures of a ported manifold that would be great.
 

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Curtis73 says what I have also been saying ever since I saw the Air Gap. I am a Toolmaker and have to be up on metallurgy for heat treating and other purposes.

The reason that aluminum is used for heat sinks is because it conducts heat throughout itself VERY efficiently. You can hold a 6 inch piece of steel in your bare hand and heat the other end with a torch, but you can't do this with aluminum. It will conduct the heat to the end where your fingers are and burn them in about 5 seconds.

The places that engine heat comes in contact with the intake (at the head flange and belly of the intake) absorb the heat and quickly conduct it through the rest of the intake. As Curtis73 said, it might take a little longer for the entire intake to reach temperature, but it will be there.

I agree that the enhanced performance of the Air Gap comes from the taller and longer runners. They give the air charge a straighter shot at the intake port in the head. This intake is a low profile, dual plane tunnel ram in effect. I wish Edelbrock would market it that way.

The "space" under the runners does make sense to people without as much metallurgy training. I can also understand that. I would like those people to hold the 6" piece of aluminum though while I heat the other end. :cool:

Racers place a bag of ice in this gap before going down the drag. NOW you are getting a cooler, denser intake charge, but the ice won't last on the street.

I have the Performer RPM intake on my wife's 331 Stroker Ford engine and the torque curve is significantly flat all all RPM's. It has a great, WIDE powerband, but also it has the cams and heads to achieve that as well, but I also credit the Performer RPM for helping with the wide band.



Steve
 

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Guy Hiltz said:
Thanks for all the replies,its much appreciated!From what I've read here I dont think an Air Gap is in my future,but I might see if I can do a little work on my own intake.DoC if you can post some pictures of a ported manifold that would be great.

I cant upload pics here, pm me your e-mail adress and i will send them to you.
DoC
 

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The edelbrock Air Gap intakes have more sweeping runners with gentle turns, and like the RPM the runners vary in internal size to produce a more smooth torque curve, even what we might call "two torque peaks".

Dual plane intakes have different flow characteristics than single planes, and each specific engine combination might like one better than the other.

Don't forget that single plane intakes make significantly less idle vacuum because they are 90* design allowing the intaking cylinder to see the open exhaust valve of the previous cylinder as a vacuum leak.
 
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