[65Mark]

Forum says “No question too basic here!” so here’s a basic question that could have differing opinions.

I’ve been told that for fuel injection you should use a single plane manifold, but also told use a dual plane. I’d like to get a definitive answer to this one. As most of you should know by now, I plan on using an aftermarket aluminum Tri Power manifold for direct port injection, the only problem is this manifold is a dual plane type and no one makes a single plane version. My thoughts are IF a single plane manifold is more desirable I will modify one to make it a single plane, but don’t want to do all the work if I don’t gain anything from it. To convert to single plane my plan is to remove the water crossover (which I plan to do anyway) and then to split the manifold in half vertically from front to rear on a band saw. That would expose the runners and the plenum for easy milling. After the milling and port work is done, including adding the injector bungs, then I would mount both halves on an engine with gaskets and torque it down, then Tig weld the manifold back together, I would have to pull it off of course to weld the bottom. Then the carb/throttle body mounting flanges would have to be milled/surfaced flat again, which shouldn’t be a big deal. Some of are you are probably going to ask what about welding the plenum where the exhaust crossover is, I plan on opening up the crossover from the bottom for access to weld and to convert the space into a distribution block for the injectors.

Ok, time to pick it apart, what am I not seeing in this picture? Any ideas? Is a single plane the best for direct port fuel injection? I will be using modified carbs as throttle bodies, but with larger CFM capacity than stock carbs, how much larger will I need to support the 600 HP that I am aiming for? The engine will be a .030 or .035 over 428, 4” stroke, with SD Edelbrock 330 cfm heads. Unless SD ported KRE’s turn out to be a better choice.

This will be a STREET car with an occasional trip to the ¼ mile Pontiac events. 4L80E Auto, 3:55 gears (maybe 3:73). I want great street performance and drivability but can live with some track manners.






Thanks in advance!!

[TheMonkey]

there was some interesting thoughts on this exact subject this Summer at Protouring. cast of characters included a lot of guys from here.

http://www.pro-touring.com/forum/showthread.php?t=30302

[65Mark]

Interesting thread, thanks for the link. Still nothing conclusive either way, or I didn't read between the lines right.Although I do have a better concept now.

[TheMonkey]

right. the sense i got from the discussion was that MPFI prob would not matter too much if it was dual plane.

one thought i have.... your situation is a bit different, because you are proposing modifying an existing manifold rather than picking between a single or double.

the manifold as it is cast has probably already been tested to attempt to keep even distribution to each intake port. if you were to attempt to modify this, it may mess up already good distribution. unless you are going to tune individual fuel trim and timing trim per cylinder, you'll want to keep a good distribution.

[65Mark]

Hence the dilemma. I wonder what it would take to tune each runner after opening the center plenum area. I guess I could do a flow check beforehand, and if the runners are even, leave it be. I just don't want the manifold to be the constricting link in the chain.

[krisr]

Unless you are racing that hardcore where 0.5HP counts, you wont notice any difference if a runner is out slightly. If you were chasing that 0.5HP though, you'd need to make sure your heads are delivering the same amount of air to each cylinder too, make sure each spark (voltage and dwell) is perfect, calibrate each injector, trim each cylinder's EGT and/or AFR, i.e. sensors in each primary tube rah rah rah...

In otherwords, you're worrying about nothing

[65Mark]

Thanks Kris! Although the work would be fun, I think you are right and you confirm what I've been thinking. I think I'll just open the throttle openings and use larger base plates on the throttle bodies. This is after all a street car.

Thanks for the help guys!!

[krisr]

Yeah, I wouldn't worry too much unless the runners have *obvious* issues. A tri-power converted EFI manifold would be cool! I personally would like to setup an ind. runner injected Pontiac manifold using IDA throttle bodies. A local company out here makes them for rotaries - http://www.efihardware.com/

[Steve C.]

Comments here might be of interest:
http://www.highperformancepontiac.co...o_results.html

And this:

Which intake manifold should I choose?

Most Mass-Flo systems give you a choice of intake manifolds. You might think that this is to give you a variety of RPM ranges, but that is not the case. Keep in mind... The RPM ranges typically associated with these manifolds (such as the RPM ranges listed on Edelbrock's website) are true when they are being used with a carburetor. Those figures mean nothing when you take that same manifold and use it in a "dry" system such as this. A good example would be the Victor Jr. for a Ford 302. Edelbrock lists this manifold's effective RPM range at 3500-8000 RPM's. That is true when it is being used with a carburetor. The fuel is being mixed with air inside the carburetor, and then the air/fuel mixture needs to travel down the intake runners and into the head. At below 3500 RPM, the fuel cannot stay suspended in the air, because the intake runners are so large, which results in low velocity through the runners. This is not the case with the Mass-Flo system. With the Mass-Flo system, the fuel is sprayed into the airpath at the end of the intake runners. The only thing that is traveling through the intake runners is air, so the size of the runners has little effect on the manifolds RPM characteristics. This means you can use an intake manifold that would normally be considered much too aggressive on even a mild engine. So why do we give you a choice? So you can get your air cleaner as high or as low as it needs to be to fit your application, and so that we can choose a manifold that matches the port size of your heads. Maybe you have a "shaker" hood, or maybe you have very limited hood clearance. Maybe you want to use a "Cobra" air cleaner, which needs to be over your distributor, but below the hood. With a choice of manifold heights, you can select a combination that will work for your application. Choose your intake manifold based on fit... not based on RPM range. We have used the Victor Jr. on several bone stock 302 engines, and it has amazing throttle response and low RPM performance with the Mass-Flo system.
From websire:
http://www.mass-floefi.com/

[TheMonkey]

Originally Posted by krisr

Unless you are racing that hardcore where 0.5HP counts, you wont notice any difference if a runner is out slightly. If you were chasing that 0.5HP though, you'd need to make sure your heads are delivering the same amount of air to each cylinder too, make sure each spark (voltage and dwell) is perfect, calibrate each injector, trim each cylinder's EGT and/or AFR, i.e. sensors in each primary tube rah rah rah...

In otherwords, you're worrying about nothing

Kris-

not clear whether you are saying not to worry about the difference between single or dual plane, or if you are saying not to worry about the effects of modifying from dual to single.

i agree on the dual -> single front, but i think the modification could have big effect on distribution.

as you know, with a carb, the AFR is mixed at the top of the manifold and then that mixture is distributed to each cylinder. with MPFI (without individual trim), each cylinder gets the same amount of fuel, but potentially different amounts of air. i was thinking that a modified manifold (particularly the amount of modifying proposed) could really knock that out of whack and have drastically differing amounts of air distribution. there was a post several weeks ago that tom vaught said that even in stock form (although not tested on a Pontiac), the differing amounts of air to each runner could be significant. << "I have seen production manifolds that have been off as much as 40% in air distribution between cylinders." >> http://forums.maxperformanceinc.com/...d.php?t=537698

as the router board for MS gets closer, i might find it in me to cut holes in my exhaust manifolds to swap the o2 sensor among cylinders and read AFR differences. or maybe use some donor headers. i'm not convinced the Tomahawk has fantastic distribution. obviously, i'll share what i find if i do that.

[amcmike]

Originally Posted by Steve C.

The RPM ranges typically associated with these manifolds (such as the RPM ranges listed on Edelbrock's website) are true when they are being used with a carburetor. Those figures mean nothing when you take that same manifold and use it in a "dry" system such as this. A good example would be the Victor Jr. for a Ford 302. Edelbrock lists this manifold's effective RPM range at 3500-8000 RPM's. That is true when it is being used with a carburetor. The fuel is being mixed with air inside the carburetor, and then the air/fuel mixture needs to travel down the intake runners and into the head. At below 3500 RPM, the fuel cannot stay suspended in the air, because the intake runners are so large, which results in low velocity through the runners. This is not the case with the Mass-Flo system. With the Mass-Flo system, the fuel is sprayed into the airpath at the end of the intake runners. The only thing that is traveling through the intake runners is air, so the size of the runners has little effect on the manifolds RPM characteristics. This means you can use an intake manifold that would normally be considered much too aggressive on even a mild engine.

Wow are they full of it!

Problem with carb is fuel out of suspension slows air velocity? Try lack of booster signal because of low velocity due to port characteristics.

Laws of physics only applies to liquids and not gases?.... sure guys. Whatever b.s. sells your systems I guess.

I never like this system the moment I saw it with the MAF sitting right in front of the throttle body. And comments like that make me want to steer even further clear of using them.

[Will]

I have to say I also have a real problem with what they're saying about RPM ranges for various manifolds.

Beyond the fuel suspension issue comes the issue of port "tuning". You need to maintain an appropriate velocity in the intake runner and port to achieve maximum cylinder filling in the RPM range where the engine makes power. An oversized intake runner on an engine otherwise designed for lower RPM power will hurt that engine's power potential because you don't have a fast moving column of air trying to force it's way past the intake valve as it closes. On the flipside, too small of an intake runner will restrict a large engine's breathing capabilities at high RPM.

Just look at the various EFI systems that GM has employed over the years. In the '80s the little smallblocks were tuned for making low and midrange power. A TPI 350 wasn't making good power beyond 5000 RPM in stock form and the TPI intake manifolds had long, small diameter runners which enhance low RPM cylinder filling. When people wanted to make more high RPM power they went to modified (larger or even partially siamesed) TPI runners. As GM bumped up the power output and RPM potential of their engines into the LT1 and then LS1 series engines the intake runners got larger.

The point of this is that while a victor manifold may work with a port FI system on a 400 designed to make max power below 5000 RPM, it is NOT optimum and will not produce the best power potential due to it not being designed to provide optimum intake tract velocity in the RPM range in which that engine will operate. I would still choose my intake manifold based on the intended operating RPM range of the engine since we don't have any dedicated FI type manifolds available to us at this time.

One thing I would probably do though, especially since it's fairly easily reversible, would be to remove the divider in a dual plane manifold's plenum. The larger plenum volume isn't going to have a big effect on air velocity in the runners. I would only worry that it might affect distribution characteristics among the runners.