Modern Single Plane Intake Flow Questions

[Joe-JDC]

Dimples seem to work quite well.  I have pictures of a couple of intakes that have had them added, and they definitely added torque and hp in back to back testing.  I don't have pictures of my FE intakes handy, but here are a couple of the Y  I tested this week.  I have seen the dimples from other builders that used a 1/4" drill bit, 3/16" drill bit, or 5/16" drill bit.  Usually the depth is just to the flute breaking full circle.  I like to place them in crisscross pattern, but straight rows seem to work, too.  I placed mine ~ .250" between dimples.  I have seen the dimples simply left as drilled, but I prefer to sand blast them with black diamond media for texture.

Below are three different manifolds with dimpling.  The manifold with the divider cut down was run on my 595 hp engine, and it lost about 30 lbft tq, and 20 hp.  The owner of that manifold did the same thing to the 289 RPM manifold that was on the 2nd place finisher in last year's EMC competition.  He said the Victor JR made more horsepower, but the RPM had better torque average so they used it in the competition.   Joe-JDC

[frnkeore]

Thank you, Joe

[1968galaxie]

Fantastic information
All I was attempting to add to the OP question on single plane FE intakes was that there is much more than equalized flowbench flow.
Also very useful to flow/modify intake with the cylinder head to be used attached. There is information there.
Fuel distribution is certainly enhanced by plenum ribs or dimples.
Carb spacers (2") also aid with fuel distribution - air/fuel has more distance/time to turn.

Thank you Joe!

[machoneman]

'Public,common,or conventional testing I’ve seen on the subject of TBI intake use has all been SBC centered.
Engine Masters just tossed the dual plane for a single and called it done. I’d hate to cut the divider away and end up worse with an intake that now requires machine work to reinstall the divider ,like Jay did for his Dyno test. Or weld in a replacement."

Well, a third way to experiment w/o welding in a divider involves machining two vertical notches in a spacer. A divider is easily fabb'ed from some aluminum plate in a T-shape, bottom of said divider closely matching the plenum's bottom. Sliding in the new spacer with and without the easily removeable divider provides easy experiementation. But yes, one must first take off the intake and remove the as-cast divider.   

[Cyclone03]

A comment I found interesting that made me think was,what works on an FE doesn’t work with other engines.

wave reflective tuning?....It seems the FE has a fairly long intake runner for its displacement ,even single planes have a fairly long runner. Talking cast intakes not tunnel rams.

For my discussion here I am in no way talking tip of the spear set on kill FE’s. I know we have some top engine builders here.

On road drivability ,low/mid range power is where it’s at for me. Brent specked my Cam last year and I would say the area under the curve is incredible . Here in TX we have a toll road that allows 85 MPH speeds. Last week I did some “tuning” (self tuning efi) From 80 (2600 rpm) I rolled into the throttle ,not a stab,to WoT (3200) then allowed it to pull I pulled to over 120! Ruled back out and down to 80 and repeated,how quick it picked up speed frankly surprised me!

With a 3.70 gear and TKO it spins the tires in 3rd gear,even 4th at 45mph!
Softening up a bit may not be a bad thing.

Im not really looking for more, the O2 sensor is in one collector so it averages the mixture , rich cylinders skew the lean cylinders even leaner. That it why balanced flow matters to me.

[TomP]

Funny thing that fuel distribution. I used to have a TunnelPort dual quad, I bought an intake at a swap meet that had a divider down the middle that was like a T. It walled off the rear two cylinders from the others and walled the left three front ones from the right three.
 Ford must have done that for a reason. When you think about it, the carbs sit backwards, so the #4 and #8 cylinders only get fed of the primary barrels on the back carb and the other six get fed off the primaries of the front carb and when the throttle opens more get fed by then as well as the secondaries on both carbs. Must have been done to solve the rear cylinders running too rich.

I ran nitrous on a plate under the 1V carb on a 200 six. It would melt the #1 and #6 plugs. That long skinny flute of a built in intake manifold was terrible distribution.

[Joe-JDC]

I just ran that toll road two ways last week, all 90+ miles one way at the speed limit, and got passed by a few who were in a hurry.  LOL  Joe-JDC

[Cyclone03]

I just ran that toll road two ways last week, all 90+ miles one way at the speed limit, and got passed by a few who were in a hurry.  LOL  Joe-JDC

It really is a great tuning road.

[Cyclone03]

So Victor or TFS or Jays Street Dominator off eBay?

[Barry_R]

I have run dual plane and single plane intakes on a LOT of FE engines.  Back to back.
On anything milder, and running under 6500 RPM, the dual plane wins on average power 90% of the time. 
I see zero reason that the throttle body EFI would make much of a difference in that trend - if any.

It's not just distribution - or air flow - it's also runner length.  The FE has long outer runners and really short center runners on single plane designs.  Average gets shortened as a result.
It's an artifact of the paired intake valves in the center of the head.  The dual plane "fixes" the difference somewhat and helps even things out.  The center runners all get longer while the end ones remain about the same.  On a dual plane an open spacer helps the carb (or TBI) "see" both sets of cylinders - make the engine think the carb is bigger.  On some combinations it also evens out the side to side A/F ratio.  If the combination wants/needs those items addressed it will pick up.  With all that noted, there are huge differences in single plane intakes.  The RPM out powered a PI on a recent build here by something around 40HP with everything else the same.

I might be wrong - won't know until you try - but on your build I bet the change to a single plane gets you close to nothing...

[pbf777]

     

I might be wrong - won't know until you try - but on your build I bet the change to a single plane gets you close to nothing...

     Remember, the O.P. was an inquiry of single-plane intakes and balance of flow values. This perhaps more of a theoretical concern, rather than an inquiry as to which design element actually would provide better realized performance.

     I do not disagree with your statements of the value of the dual-plane, and yes with the fuel being presented early in the gas column (carburetor or T.B.I.) often much of the resultant evidence of deviation in the air/fuel mix delivery is masked; but consider that invariably with the complications in port runner configuration of the dual-plane, particularly as the density and velocity of this gas column is increased, the dual-plane is more likely to falter in values of an equal or balanced delivery of atmosphere, and fuel, as compared to the single-plane arrangement.   

     Also, with the use of T.B.I. one is effectively negating the difficulties often encountered with the 360° vs 180° plenum intakes, with the effective drafting of fuel from the carburetor; this perhaps also a consideration in the determination of selection.   

     Scott.

[pbf777]

Fuel distribution issues arise when the fuel hits the plenum floor and is not directed in a clear path to a port.  ...................   The single planes were the same manifold, but one was stock, and one I ported.  The stock single plane had a plain floor, and at the top of the dyno pull, fuel was seen actually swirling and misting above the carburetor due to fuel bounce back on pulsation of the wave lengths. The ported single plane had dimples in the floor, equal flow in each runner within 4 cfm, and did not have any fuel mist or vapors swirling above the carburetor at the top of the rpm pulls................    Joe-JDC

     Interesting, but I am curious as to the effect of either the dimples in the plenum floor or equal port runner flow would have on the visible fuel vapor witnessed above the carburetor ("stand-off") in operation?  Since stand-off is a resultant observation of the reversionary effects in the gas column initiated upon by the operation of the intake valve, and is carrying the fuel volume along for the ride. So if the dimples managed to place more fuel in suspension, within this air column, then more would be in motion, in both directions, perhaps?  And perhaps the most one would expect from an imbalance in port flow sums might be a loss in resonance from port to port, perhaps if great enough, even dampening the observed effect? 

     Please note that I am approaching this with inquiry of others experience, for my own edification, and perhaps others.         

     Scott.

[frnkeore]

Although I dislike TBI and think that if you go injection it should port injection, I think the OP is asking the right questions.

"the mixture distribution is noticeably uneven."

"So I guess I'm asking which of those two have the smaller runner cross section."

Air flow is one thing but, when you add fuel to it, it's not the same. The following is the Approx weight of each:

Air = .0807 per cubic ft @ 68F (depends of the make up)

Gas = 46.9 per cubic ft @ 68F (ave of 2 sources)

So, gas is 581 times heavier and can't follow the exact same path as air will, by it's self, because of it's greater wt. Many manifolds have failed because of that problem.

But, if you can keep the velocity up, with smaller runners and with a straighter path, you have a better chance at keeping the mixture together.

Using that assessment I think a Street Master could help, at least at 3000 rpm and above. There may be better ones, both single and dual plane but, that one, I think is well designed.

Large runners and tight corners, won't work as well.

[Cyclone03]

No ideas on flow of the modern single plane FE intakes?
I thought somebody here would have tested them.

[Gaugster]

Sorry that I don't have much to add to this thread but since we are in the technical section I'd like to expand on one of the tangents. 

The weight (lbs) per cubic feet numbers.... for air (vapor) and gasoline (liquid) do divide to 581 but that's exaggerated quite a bit. The only way I can think of to compare apples to apples (vapor to vapor) would be to recall that we want something like a 13:1 A/F ratio for max power. (Just picked a value - not making a claim) This is a ratio of air mass to fuel mass. So while still an over simplification (weight vs mass and an average per bank of cylinders) the 581 divided be 13 is more like 45. Still the gas is heavier and flow will differ. You get a "wet" intake with a carb/TBI but a dry intake with MPI since the fuel is introduced way downstream from the plenum. I don't know what to make of the wet vs dry intake condition other that a dry intake might be more prone to carbon build up. Can a MPI system with an O2 sensor in each header really adjust fuel per cylinder? Or is it limited to each bank of cylinders?