TKOPerformance wrote:

might be hard with hood clearance being what it is in a Mustang
 

Thanks for the input.  I wish it was Mustang hood clerence.  Its the 393W in the Galaxie and the hood clerence is even worse.

I don’t have throttle body injection…I have had factory CFI (84 Cougar) and TBI (95 Z71).

Most of my driving was well below 6000 rpms.

One of the things I noticed is the location of the fuel injector(s) in relation to the throttle blades.  Basically mimicking the carburetor spray location.

For a low rpm engine that may spin up occasionally for fun, I would go for a dual plane and as suggested a spacer or divider wall milled down.

Another option I looked at is to modify an existing dual plane into an open single plane(ish).  It wont be a true dual or single.  By doing this, you would have the smaller runners for low speed and have the open plenum where the fuel is sprayed and distributed.

You are still carrying fuel down each leg to the cylinders like a carb.

All of the single plane intakes for 351w are tall for high rpm use…at least what I have seen…unless some expensive custom made piece.

Edelbrock Performer and Performer RPM (non air gap…RPM air gap is taller) will fit under stock Mustang hood according to Edelbrock installation instructions.

Just fuel for thought.

That MotorTrend article seemed to indicate that the loss of low end torque is small with EFI because it doesn't depend on a vacuum signal for fuel delivery.  So I think either choice would work.  The first manifold would not require any modification though.

The Blueprint Engine I have on order with the Sniper EFI states it has a 'dual plane' intake.

I’m in the process of switching to EFI (Holley/MSD “Atomic 2”, when it finally becomes available!).  I plan to use my existing Edelbrock “RPM Performer” intake, 351W.
Hood clearance is tight with the existing Holley 600CFM carb, I’m using a phenolic ½” spacer (4-hole).  The Atomic 2 throttle body is nearly the same height as the Holley, so I’m not expecting that issue change much.
I will update when the installation is completed.

On my 65 with a 298 Im using the Performer with Holley EFI and a stock air cleaner, I didnt think there was room for the RPM and I wanted as much low end torq as I can get with my 2;80 tall gears. From everything I have read single plane gives you top end torq and dual plane gives you low end torq. I run in the 25-3200 RPM  range

I'm running a Performer 351 w/Fitech EFI and Control Center. No spacer and 2" air filter. that's all I can fit under the hood.  I don't know about which manifold is better, but I get great response and hot/cold startup are perfect.  Much better than the carbs I have used in the past.  It pulls from 1200 RPM just fine.  No way a single plane manifold will fit under there.

And, thanks for getting me off my butt and look around the engine.  I noticed signs of age hardening on some of the rubber connections. I need to get new ones.

Can you run O2 sensor for each side?

I forgot about the Torquer II…perhaps lower the 4150 base as needed?

Last edited by Nos681 (4/21/2023 4:25 PM)

Even with an O2 in each bank you're still only getting an average.  Possibly a slightly better average, but an average nonetheless.  In the end, TBIs have a lot of the same issues as carbs in terms of mixture distribution, etc.  Its why everything went to port EFI.  Give it another 20 years and everything will be direct injected like a Diesel. 

Compared to a carb, with TBI you get better fueling across a range of conditions because it can self adjust.  You get better mileage across those conditions.  You get better cold starts and don't wash the cylinder walls down as much with raw fuel.  They never need to be tuned or adjusted beyond initial calibration.  They are still pretty simple and therefore reliable. 
 

TKOPerformance wrote:

Even with an O2 in each bank you're still only getting an average.  Possibly a slightly better average, but an average nonetheless.  In the end, TBIs have a lot of the same issues as carbs in terms of mixture distribution, etc.  Its why everything went to port EFI.  Give it another 20 years and everything will be direct injected like a Diesel. 


Compared to a carb, with TBI you get better fueling across a range of conditions because it can self adjust.  You get better mileage across those conditions.  You get better cold starts and don't wash the cylinder walls down as much with raw fuel.  They never need to be tuned or adjusted beyond initial calibration.  They are still pretty simple and therefore reliable. 
 

I agree the TBI is much like a carb only it is opening all 4 all the time mixing fuel much better for the ports than a carb that could run lean on the back 4 while on low settings. I dont see the benefit of the spacer as it seams it would just be making it into a single plan. I have so much more throttle response with my sinper then I did with my eldie carb that was also new and dialed in.
As for the O2 sensor, one is enough as most dont even have 1 with a carb and its for the tuning that the EFI does on its own. 

Last edited by Cab4word67 (4/21/2023 9:59 PM)

Cab4word67 wrote:

As for the O2 sensor, one is enough as most don't even have 1 with a carb and its for the tuning that the EFI does on its own. 

The problem that we are talking about regarding o2 sensors is it is an average.  It is reading 4 cylinders and adjusting accordingly,  but if one is very lean and one is very rich the EFI thinks everything is okay but the cylinders are still out of wack.  That is what I am trying to avoid and the reason open plenum is recommended. Two O2 sensors might get a better read one on each side.  If you watch any dyno testing shows like engine masters where they put an o2 sensor in each header pipe you can see the disparity.
 

Daze wrote:

Cab4word67 wrote:

As for the O2 sensor, one is enough as most don't even have 1 with a carb and its for the tuning that the EFI does on its own. 

The problem that we are talking about regarding o2 sensors is it is an average.  It is reading 4 cylinders and adjusting accordingly,  but if one is very lean and one is very rich the EFI thinks everything is okay but the cylinders are still out of wack.  That is what I am trying to avoid and the reason open plenum is recommended. Two O2 sensors might get a better read one on each side.  If you watch any dyno testing shows like engine masters where they put an o2 sensor in each header pipe you can see the disparity.
 

The issue with fuel distribution isn't so much single vs. dual plane, because you still have a runner length disparity.  The carb or TBI is located in the center of the manifold, so the runners to the center cylinders are shorter than to the cylinders on the ends.  It may not seem like much, but the issue is that the air and fuel is properly mixed right under the carb or TBI.  The farther the mixture has to travel the more likely that the fuel falls out of suspension.  Atomized fuel burns completely and efficiently.  Liquid fuel doesn't.  This is why port EFI was such an upgrade from TBI.  The runner length disparity has been more or less eliminated and its spraying fuel directly into the intake port at the back of the intake valve.  There may still be some port to port variation due to other factors (good port systems often have a fuel trim feature where you can adjust cylinders individually), but overall the variation is greatly reduced.  This is also why the next step is to go away from port and go to direct injection, which some gas engines already use. 

On a dyno technically those aren't O2 sensors they're pyro probes.  O2s are measuring resistance change relative to temperature.  Pyros are just reading temperature directly.  Pyros are cheaper than O2s and use a smaller bung, while still being very accurate.  The output is the same though, mixture determined by exhaust gas temperature. 

All kind of academic, but the point is that the runner length difference is typically less (shorter runners) and the flow runner to runner more balanced in a single plane.  With a TBI the closer you can get the TBI to the ports the closer it is to port EFI.