Ford 385 Series Engine Builders Forum: My MPFI Intake Manifold Conversion

This is what I've been working on for the past two weeks. It's an Edelbrock Performer RPM 'Air-Gap' intake manifold which has been perfect for my engine combination. I'm not falling for the usual claim, "single-plane is acceptable, since it's now only flowing air." Airflow port dynamics still apply; big open plenums and short large runners aren't good for low to mid RPM torque. This is a heavy off-road truck and the engine must be built as such.

Because it's a dual-plane manifold, there was a considerable amount of welding required to make the MPFI conversion possible. The runners are angled differently and at various heights. I wanted the injectors positioned at the very end of each runner and as low as possible. I don't like injector bungs, so the injector port drill bit http://www.rossmachineracing.com/injectortool.html from Ross Machine Racing was my best option for machining the manifold injector holes and the fuel rails. Injector bungs position the injectors up too high and not quite far enough out, toward the end of each runner (due to their large diameter). I purposely positioned my injectors at the very end of each intake runner (welding required), so they inject fuel directly into the intake ports. My injectors are actually positioned almost an inch further, toward the end of each runner, than most MPFI conversions I've seen. I couldn't angle the injectors toward the intake valves, simply because there isn't enough clearance and I'm not convinced that spraying fuel at a hot intake valve is beneficial. I believe fuel can atomize better with increased travel distance.
NOTE: The additional o-rings on the bottom of each injector, are just there for gap aesthetics/dirt shield/supplemental support.

I also purchased blank fuel rails http://www.rossmachineracing.com/dash6.html (1/2" I.D.) from Ross Machine Racing and machined them myself. I threaded the ends of the fuel rails to 3/8" NPT after enlarging the ends to 9/16" using a step drill bit. The fuel rail hold downs are made out of high grade, 1/8" thick stainless steel (difficult to drill) and are very rigid. I can literally grab hold of a fuel rail and swing it around! Most people wouldn't dare do that. They're very strong. Also, they're vertical hold-downs, not horizontal like most of the flimsy stuff I've seen. The crossover line is an Aeroquip -8AN AQP socketless hose with 90° fittings. My engine is blue & aluminum in color, so the intake manifold assembly looks great.

The former TBI unit was converted to an MPI throttle body (1000 CFM) with extensive welding and porting.
You can read about it in this link http://www.chevytalk.org/fusionbb/showtopic.php?tid/239004/
I'm using 42 lb/hr injectors http://www.summitracing.com/parts/SUM-240042/ - Standard Motor Products/Summit Racing
with a Holley #512-504-5 fuel pressure regulator http://www.holley.com/512-504-5.asp

Holley Dominator EFI system http://www.holley.com/HolleyEFICatalog/
dual WBO2 sensors http://www.holley.com/554-101.asp
dual knock sensors http://www.chevytalk.org/fusionbb/showtopic.php?tid/249317/
fuel & oil pressure transducers http://www.holley.com/554-102.asp
VSS sensor http://www.chevytalk.org/fusionbb/showpost.php?post/1996571/
custom 60-2 trigger wheel & crank sensor http://www.chevytalk.org/fusionbb/showtopic.php?tid/238915/

I should clarify that my engine has been under Commander 950 EFI control for years and I recently upgraded to their Dominator EFI system, using my existing TBI hardware. This latest upgrade was solely for the purpose of converting to multi-port injection, from my previous throttle-body injection. My TBI system was very well tuned with the C950 & Dominator ECU, so I'm not expecting much improvement just by converting to MPFI. I'm sure a lot of you would be pleasantly surprised to realize how well Holley's TBI systems perform.

The new Holley EFI systems are capable of four types of injection strategies:
* Bank-to-Bank - Fires half the injectors and then the other half every 180 crankshaft degrees (injectors fire once per revolution).
* Untimed Sequential - Fires each injector every 90 degrees. But since there is no cam sync signal, it is random which cylinder is first triggered.
* Paired - Similar to Bank to Bank, except only two injectors are fired at a time (fires a pair of injectors every 90 crankshaft degrees).
* Sequential - Fires the injectors in sequence of engine's firing order (requires cam sync sensor).
I've initially chosen to run the engine using the Paired injection strategy. However, I've already installed a custom 60-2 trigger wheel & crank sensor (installed but not yet enabled), so the plan is to "fine-tune" the new MPFI setup, then convert my distributor's Hall-Effect sensor to a cam sync sensor, so I can run in full Sequential mode. We'll soon see if the MPFI makes any difference in idle quality.

[linked image]

I received several emails in reference to some confusion about the visible o-rings, so let me clarify. The additional o-rings you see on the bottom of each injector, are just there for gap aesthetics/dirt shield/supplemental support. They're not sealing anything. (Now there's actually three o-rings on each injector.) The injector port holes are machined into the manifold just like the I.D. of injector bungs. The injectors are o-ring sealed (top & bottom) as they were designed to be. I aluminum welded enough material to make all the runner ends the same height AND to have enough depth for each machined injector hole. All the info is in the first post. Here's a video of how I machined the injector holes in the manifold & fuel rails:
http://www.youtube.com/watch?v=iSNb9QKj568
[linked image]

I also received a few emails/PMs in reference to the welding I did at the end of each runner, so let me clarify a few points. In order to machine the injector holes into the intake manifold, I needed eight equal height, flat platforms at the end of each runner. I aluminum welded enough material, where I was able to cut off the top of each weld, the exact same height. I did this by carefully sliding the manifold against a spinning die grinder cut-off wheel in a drill press. (Other home machining operations can be accomplished with various carbide burrs, cut-off wheels and a drill press.)

Afterwards, I ground each surrounding area smooth, contouring to the shape of each runner. FYI: The Alumacut carbide burrs from CarbideSelect.com http://www.carbideselect.com/burshpescuts.php are the best aluminum grinding burrs I've ever used! Once I had eight, nice looking flat bosses, it was a simple matter of machining the holes with the injector drill bit pictured above. This allowed me to install each injector into the manifold (just like you would if using injector bungs) but without using injector bungs. The money saved by not purchasing injector bungs, went toward the cost of the injector drill bit (which was still required for the fuel rails anyway). There's nothing to see inside each intake runner, except for the smaller diameter hole (see injector port drill bit). This is another advantage of not using injector bungs: the injector nozzles are about flush (slightly recessed) with the roof of each runner and there's no grinding work required inside each runner.

The fuel rails are much easier to machine since they can be clamped in a drill press vise. The only issue I had was drilling & tapping the ends to 3/8" NPT because the I.D. of the rails is 1/2". You can't simply drill a 1/2" hole to the required 9/16" (for 3/8" NPT); the bit is too unstable. So I first made a pilot hole using a Unibit step-drill bit http://www.mytoolstore.com/klein/59001.html then drilled the 9/16" hole, in about 3/4" for tapping 3/8" NPT. I purchased 3' of Aeroquip -8AN AQP socketless hose with 90° fittings to assemble the single fuel rail crossover line/hose. The arch in the hose is there to clear the distributor. My engine is blue & aluminum in color, so it looks good too.

This is how I mounted the knock sensors on each side. I custom made a 90° knock sensor adapter to mount the knock sensor close to the lower block. I made it using a 90° 1/4" NPT brass fitting. Simply cut off the male threads and drill straight through using the appropriate drill bit (for 3/8"-16 or 7/16"-14 bolt). I mounted it on an existing raised threaded boss with a grade 8 bolt. The advantages are; the knock sensor hugs the side of the block (providing the necessary starter and/or header clearance), it swivels to aim it toward the optimum angle (aids in routing the wire) and it doesn't require draining the coolant. My datalogs prove it's functional.
[linked image]

I have a theory that every new (carbureted) intake manifold made, should have cast injector bosses. We're living in the year 2010...electronic fuel injection is not going away! At least Trick Flow had enough sense to cast bosses with 'level tops' onto their Track Heat intake manifolds, so the end-user can easily drill injector ports (using the same aforementioned tool I used).
[linked image]

http://www.trickflow.com/partdetail.asp?part=TFS-53400111&autoview=sku

May God's Grace Bless You

'78 BRONCO: 508" stroker, TFS heads, Dominator MPFI, A/C, Lentech Strip Terminator wide-ratio AOD, 3:1 Atlas II, max built Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim-flip steering, 4" lift, 35" tires

My MPFI Intake Manifold Conversion

Holley DIS & Sequential EFI Upgrade

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