What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Dual VS Single plane with TBI style

K85 Octane

K85 Octane

People Fatigued
 Premium
GMOTM Winner
Joined
Nov 2, 2009
Posts
15,360
Reaction score
5,959
Location
San Bernardino CA
Picking some brains with this one.
Bender has always had a dual plane Pro Products intake with FAST ez efi. I never really questioned it since the combo worked.

I believe the TBI needed a spacer to miss the old EGR. That spacer was an open throat 1/2-3/4" spacer. So technically all cylinders could have been fed by the TBI, though not efficiently because the intake manifold has a split between the two planes.

With the engine in Plank, I don't need nor what the spacer. Would I get better performance from a single plane intake (open throat) when using the TBI/ EFI body? This is a truck engine, set up for grunt, not rpm.

PS> I have not found this style of intake from Edelbrock. It might have to be modified as Im using the TPI straight center bolt heads. Don't need EGR anymore.

Thanks guys!
 
Personally, I would try it and see. The old '72 K5 had an Edelbrock dual plane under the GM TBI with an adapter. I believe that it had a TBI spacer as well, can't remember. I liked how that engine ran then. I have been fighting to get the same performance out of it since installation of the PF4. I may be getting closer now with the help and research from @Bent77
 
Would need some pictures of the intake
Center bolt heads have at least 2 different intake patterns

The issue with going full open is you lose bottom end over a dual plane
Using a true separation on the dual plane with TBi often leads to rich cylinder and lean cylinder issues
I think it’s less noticeable on engines closer to stock
 
I am NOT in a position to just "want and buy" parts right now LOL but I do want it to work. I might be able to add the spacer if it doesn't seem happy...later. For now no.

What helps me is the FAST body has 4 butterflies and 4 injectors, so it can dump quite a bit on either side of the intake wall. As for bottom/ top end... well this 400sb (in its life) has never been in a lighter car hahaha

I think this is it. Uses shims for the center 4 bolts to angle them straight down. HOWEVER, mine has the divider all the way up. Wonder if some grinding could have helped before I assembled.
IMG_4482.jpeg
 
I'm running a similar aftermarket TBI fuel injection (Aces Killshot). I haven't had any issues with my dual plane intake (Edelbrock Performer RPM). The main thing you need to pay attention to is how the MAP sensor gets its signal. If the MAP sensor is only reading one side of the dual plane, it won't be able to determine engine load accurately which will result in drivability issues. My factory Quadrajet gasket gives mine about 0.25" clearance which is plenty for the MAP sensor to get a good idea of overall engine load.

This is a picture of the Aces Killshot TBI, I circled the port where the MAP sensor gets its signal.

Screenshot 2025-12-18 230014.png
 
Gm tbi was dual plane intake .

Wet flow tends to be better with dual plane . Once you go port injection like proflo 4 or others then you can go single plane as it just moves air only .
 
sweetk30 said:
Gm tbi was dual plane intake .

Wet flow tends to be better with dual plane . Once you go port injection like proflo 4 or others then you can go single plane as it just moves air only .
Click to expand...
Actually the opposite
Wet intake works better on single plane due to the fuel distribution. As tested on engine masters

But it begets a riddle. Why did the two wet injector GM TBI seem to not have issues?
Hence the comment that I made early about stockish engines not having the issue

Dry intakes of a dual plane configuration seem to be exceedingly rare
 
I run a Summit max-efi, which is a similar 4 barrel design, with a one inch open spacer on a dual plane Edelbrock performer EPS, on a mild 350. It works great.
I saw a video which I think was horsepower TV or one of the like, were they recommended running the spacer, with this type of fuel injection on a dual plane.
 

Single plane vs dual plane intake using performance throttle body EFI

So I decided to start a new thread since a discussion has surfaced in @Chevy305 's EZ-EFI upgrade thread here starting at post #15... https://ck5.com/forums/threads/ez-efi-1-0-upgrades.333912/ Rather than simply guestimating and being a spectator, I decided to dig into it a little more so we...
ck5.com ck5.com
 
@folkenheath thank you!

Cliff notes
So check the fresh plugs after it's been on the street for a while.
See if there is a difference in banks.
Don't try to fix it for free by removing the wall between the planes.
The Blazer drove and idled smooth, same inside the Nova minus "driving". BUT the Blazer had the carb spacer.

I suppose if I can score a single plane intake that works with my heads, I'll definitely do it if I see the wild difference in plugs that Heath saw.
 
K85 Octane said:
@folkenheath thank you!

Cliff notes
So check the fresh plugs after it's been on the street for a while.
See if there is a difference in banks.
Don't try to fix it for free by removing the wall between the planes.
The Blazer drove and idled smooth, same inside the Nova minus "driving". BUT the Blazer had the carb spacer.

I suppose if I can score a single plane intake that works with my heads, I'll definitely do it if I see the wild difference in plugs that Heath saw.
Click to expand...

No problem!

I typically say if you already have the intake on then just try it with EFI, but if you are buying an intake or swapping one for the EFI, then go single plane, and a Volcano insert can't hurt to get some more ow end torque with the single plane.

Then again, if you are buying a new intake and EFI you may be better off with Edelbrock PF4 or Holley MPFI, because you are closer to the cost when buying an intake too.

We might want to put any info you gather with your combo in the original thread to keep it in one place?
 
I've been running the EZ EFI 1.0 since 2013 I think, still using it on the 406. Does fine but always wondered if it could be better with a single plane after reading some other things. Now that the vehicle AROUND the engine is 3,000+lbs lighter, I wouldn't worry about low end.

Just thought about that. This drivetrain was powering heavier than 2 NOVAs lol Still a smogger engine, nothing exciting, but now with 3,000lbs less steel! :D
 
Yeah, it can run OK with the dual plane, acceptable performance. But it ran more optimal with the single plane. And with the dual plane and the EZ, I had to reset it every couple years or or would eventually learn wrong and then at part throttle it wouldn't run satisfactory any more. The other systems you can shut learning off once it runs good, you could avoid that. I did not have to reset it after going single plane.
 
@folkenheath recommended a single plane manifold (with the Volcano insert) running the Holley TBI on the 502BBC he built, tuned and dynoed for me.

The results speak for themselves. Brutal TQ from 2000RPM to redline.

Heath knows his stuff… would certainly take his suggestions seriously.

-G
 
Dumb experiemental questions

You this it will run better or worse with this wall chopped out? I don't see selling the intake for much anyway so I don't mind trying IF it won't HURT performance lol

IMG_4528.jpeg
 
K85 Octane said:
Dumb experiemental questions

You this it will run better or worse with this wall chopped out? I don't see selling the intake for much anyway so I don't mind trying IF it won't HURT performance lol

View attachment 519926
Click to expand...
That is what @folkenheath was talking about.
I don't think you even need to go all the way down, halfway maybe
 
If you do it do not go all the way down. Maybe an inch tops. I think if you have room you are better off adding a 1" open spacer instead to not only give it that gap, but also more plenum volume and more height for the turn. It's also easier to remove.
 
Would this work? I can watch this, maybe throw out a lowball offer. Would I need to set this up in my drillpress to "straighten" the 4 center bolts?
Thanks guys!


IMG_4530.png
 
:D pulled the trigger
Tried for $50
Waited a month and sold a couple parts and offered $75

Planning to run the spacer as I have the hood clearance. I will have to check throttle rod/linkage to see if it will work.

Right now, that nipple is stuck in there. Heated the aluminum and still stripped using a socket. It has to come out, I need the port for a sensor :(

IMG_4567.jpeg
 
You must log in or register to reply here.

Latest Posts

Top Bottom