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Discussion Starter #1
Hey guys, I am planning on swapping my intake from my weiand stealth to a single plane. Apparently throttle body injection really prefers the single plane intakes for a bunch of reasons.

I have always run dual plane intakes, then again I have always run carbs. So trying new things can be a good thing I suppose. Anyways, like I said I don't have a lot of hands on single plane experience and thought I would ask those that might. The car runs fantastic honestly, but it does have a slight stumble on low speed take offs that's annoying in traffic, and I am told I am leaving power on the table with the dual plane.

The car is built for optimal street driveability and manners, along with wringing it's neck in the canyons most weekends. My engine specs are below.

331 stroker (roller block), comp 266H cam, 10.6:1 compression, EZ-EFI 2.0, AFR renegade 185 heads.

I have always been sort of a weiand guy, in fact I have run the stealth on just about all of my windsors. But open to the possibility of any brand really.
 

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You do not have enough cam to make use of a single plane intake in my opinion. How about adding a 1" open carb spacer and see if it helps. If you really think a single plane will work look into the Torker 2.
 

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Discussion Starter #3
It's really more about even fueling from what I am being told by the TBI experts. Apparently the "normal" rules of single vs. dual don't totally apply when it comes to this style of EFI. They even claim I will get a better idle and driveability as well as increased bottom end / mid-range power.
 

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I await your findings Ryan, I have a port matched Vic Jr sitting in a box that I replaced with an RPM air gap that gave my 347 more low end and driveability, but that is with a 750 dbl. Haven't run my FItech set up yet. Hoping I am in the "no issues" camp.
 

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It's really more about even fueling from what I am being told by the TBI experts. Apparently the "normal" rules of single vs. dual don't totally apply when it comes to this style of EFI. They even claim I will get a better idle and driveability as well as increased bottom end / mid-range power.
Depends upon how big the throttle body is. I would think single plane
would be considerably easier to tune for the mixture irregularities that
a dual plane is bound to have.
Looks like everything (fuel and air) comes through the TB on your setup.
I'm sticking with my answer......
Cmefly might be right about the Torker 2.
 

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Discussion Starter #7 (Edited)
I went ahead and pulled the trigger on a Weiand 7515, should be here sometime this week. So hoping to have time to swap it over during the long weekend. Just to clarify on the situation, other than a mild stumble on light throttle from a stop the car runs fantastically. This is truly an experiment to see if I can get it to run even better.

GT289 that's pretty much the reasoning from the TB injection tuning wizards. The ECU has an easier time self-tuning and perfecting the AFR to the needs of a single plane. The general consensus seems to be, yes it will run just fine on a dual plane, but a single will take better advantage of the ECU's ability to optimize the AFR. And for less than $300 to swap and try why not?

I figure with the relatively small size of the 7515 I shouldn't really be giving up a ton of power down low particularly with an optimized AFR. With my relatively mild 266h cam this felt like a good option, and it's also a god fit for my RPM range and even my intake port size, and as I have mentioned I'm kind of a Weiand guy.

At the very least it may prove helpful or informative as I know a lot of people seem to be switching to TBI of all different types. And despite all the research I did before making the swap, the favorability of single planes never once came up. So if I can be a lab rat for others and possibly improve my car at the same time, it's worth losing a set of gaskets over.

EDIT: for those interested here is a thread over on CPGnation about the benefits of one over the other. MODs if this is against some sort of a rule please feel free to delete and sorry about that.

http://www.cpgnation.com/forum/threads/ez-efi-2-0-and-intake-manifold.23302/

http://www.cpgnation.com/forum/threads/ez-efi-2-0-injection-with-dual-plane-intake-vs-single-plane.25871/
 

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I've been doing some reading about this and one theory why some TBIs seem to prefer a single plane to a dual plane is that on some dual planes, like the Stealth, the plenum goes all the way up and effectively splits the manifold in 2, making it difficult to equalize the intake charge across both sides of the engine, which then causes less than ideal fuel distribution with a TBI.

You might try running an Air Gap (the plenum is cut down on the Air Gap) or milling down the plenum on your Stealth a little bit and see how that does before going to a single plane.

Either way, I am interested in your test results. :smile2:
 

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Discussion Starter #9
I've been doing some reading about this and one theory why some TBIs seem to prefer a single plane to a dual plane is that on some dual planes, like the Stealth, the plenum goes all the way up and effectively splits the manifold in 2, making it difficult to equalize the intake charge across both sides of the engine, which then causes less than ideal fuel distribution with a TBI.

You might try running an Air Gap (the plenum is cut down on the Air Gap) or milling down the plenum on your Stealth a little bit and see how that does before going to a single plane.

Either way, I am interested in your test results. :smile2:
I really thought about doing that with my stealth as I have a friend with a mill and it wouldn't take him much effort to do it. But in all honesty a lot of this is for the experimentation of it. Plus I am sure I will build another street carb windsor down the road at some point. And I might end up having a practically brand new Stealth intake to squirrel away when that time comes. Or if I don't like how the single plane works I can swap it back over in an hour or two.
 

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The carb spacer idea was a good one and would accomplish the same thing as milling down the plenum. Might be worth trying that before swapping intakes just for shi!s and giggles to see what that does.

If you want to start a Go Fund Me to cover the cost of dyno testing it as is, with a carb spacer and then with a single plane, I will happily contribute!:smile2:

I am going to build the exact same engine as you, so I have a vested interest in your results! :smile2:
 

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I was going to suggest the 7515. I ran one on my mild 289 when it was on the road, I never noticed any loss in bottom end. I don't think you'll be giving up anything on a 331.
 

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Discussion Starter #12
The carb spacer idea was a good one and would accomplish the same thing as milling down the plenum. Might be worth trying that before swapping intakes just for shi!s and giggles to see what that does.

If you want to start a Go Fund Me to cover the cost of dyno testing it as is, with a carb spacer and then with a single plane, I will happily contribute!:smile2:

I am going to build the exact same engine as you, so I have a vested interest in your results! :smile2:
That's very generous of you, I will post whatever results that I can. I agree the spacer idea was a good one.

FWIW if you are going carbureted I am really happy with the Stealth in general. And the motor in general for that matter it's a great balance of useable power and driveability.
 

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That's very generous of you, I will post whatever results that I can. I agree the spacer idea was a good one.

FWIW if you are going carbureted I am really happy with the Stealth in general. And the motor in general for that matter it's a great balance of useable power and driveability.
My current plan is FI, probably FiTech, hence my interest in your results. :smile2:

Are you running power brakes? If not, do you know what your vacuum is at idle?
 

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Discussion Starter #14
I am running 2007 GT brakes all around with a daul 7" booster. Honestly needs a dual 8" will have to get back to you on Vac at idle. Haven't measured it since I set my initial timing and that was about 2 or 3 years ago. The 266 cam is pretty mild so Im sure it's enough for power brakes.
 

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If you aren't switching to a single plane for outright flow then I would think the X-CELerator (7515 as mentioned above) would be good. It would accomplish what you want and give you more hood clearance if that's at all an issue. If you are worried about flow it can always be ported. An open spacer would probably help a lot though.
 

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Discussion Starter #17 (Edited)
It's definitely not a switch for all out flow. In fact the relatively modest volume of the 7515 is why I think it will be a good fit and glad to see that you guys seem to agree. I think it matches my current parts and goals well. The goal is even better drivability and even fueling without giving up power. Which I know conventional wisdom would say that a single plane is going backwards for those goals. But, with TB fuel injection those in the know that tune and install these for a living all seem to agree that conventional wisdom does not apply with TBI. My motor is lowered so not too terribly concerned about hood clearance. But the 7515 is a bit taller than my current intake. Last time I measured I had a ton of room between my air cleaner and hood so I should be good.

*Only reason I measured is because my next little project is making a "carb tray/scoop seal" for my throttle body so that the GT350 scoop is functional. Don't really expect any "ram air effect" but would like it to be able to get fresh air not found under the hood. Particularly with how tight my hood fits it gets fairly warm under there, Im seeing intake temps of around 113 on average and am curious to see what some ingenuity/fabricating can get that down to. Plus I think it will be cool looking. But thats another plan for another day.
 

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Discussion Starter #18
Just got my 7515 intake in. Wow, Summit is quick sometimes. So that's the good news. Heres the bad news. Holy crap is this thing going to need some port work. I had been told it was a pretty rough casting out of the box and people weren't kidding. Right now I am trying to decide on the best way to handle it. Really don't want the car torn down for too long and I have about 2 months before my big trip up to Monterey. So need to decide how to move forward.

1. Port the 7515 and install and hope I like it
2. Install as is just to test out the single plane theory then port and reinstall if I like it
3. Send it back and see if I like a torker 2 would be a better call, as was suggested

I think I am going to do a bit of research on the Torker 2 and go from there. I havent ported an intake in a few years but my estimate would be that it needs at least 2 or 3 solid days worth of work to get it where I would be happy with it. It's not time I mind spending but if there is a better starting point then I would rather go that route.
 

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I don't like the choices for single plane intakes for your combo. Intakes designed before after market heads have really poor flow. When heads like the 185afr's came out it required new, better flowing intakes. The modern dual planes flow better than most old school single planes. I would try cutting down the divider first.
 

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Discussion Starter #20
I agree with you Brian. I can't help but feel like the 7515 will end up being a bottle neck. However It is really about even fuel distribution and I don't feel like just cutting the divider will do that sufficiently.

I'm also looking in to a Vic JR at the moment as I believe it will flow more CFM. People do seem to really like em'! Apparently the TB EFI's injectors pulse at around 40PSI which helps overcome the "lazy" low RPM flow of a larger single plane. So you end up not needing the smaller volume to keep velocity up. Which is why I am now leaning towards a larger intake.

EDIT!!! Scratch that, just did some comparisons and the runner size between the Vic JR and the 7515 appears to be about the same. I imagine what is different is the common plenum volume. Which EFI doesn't really need more of, it's already so well atomized.

I think I am way over thinking this at the moment to be honest :( Iv'e done so much reading today that I feel completely mixed up. And I feel like everything I know from carbs is kind of out the window.

I did put a call in to AFR to ask them for a recommendation. But all of their tech guys were in a meeting.
 
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