Fast355

iTrader: (2)

Thats right I have a new intake setup in the works for my 350 Vortec TBI in the Van. Its based on the MPFI Vortec intake I have sitting in the garage and an idea I got from the Crossfire Vault. It will involve fabricating a 1.5" tall spacer for the manifold out of phenolic as well as fabricating an phenolic lid for the manifold. The MPFI setup will be stripped from the lower intake. That will leave me with a nice Vortec specific cross-ram manifold. Distributing the air/fuel mixture will be two small block chevy TBI units with ultimate TBI mods and super common 61# 350 injectors. This should give me a free flowing manifold with a reasonable runner length and cross sectional area, 900+ cfm of flow, and 240+ lbs/hr of fuel, as well as EGR compatibility (albeit linear EGR valve). The TBI units will be one in front of the other, inline, right splitting the difference between the intake ports. That should give pretty good air/fuel mixture distribution.

Here is the inspiration

http://www.crossfire.homeip.net/cfte...ID=18&CAT_ID=1

Here is the manifold in question







Also I might mention the camshaft is getting changed yet again, to a custom ground Comp Xtreme Hydraulic Roller. 276/288 @ .006, 224/236 @ .050, .503/.521" lift, 114* LSA.

Finally getting away from the 3.08s now.

Are we ready for a street-able 450 HP TBI 350?

BMmonteSS

Not to get off topic, but how exactly do the injectors work on the vortec MPI system? I thought it used a central injector unit with hoses running to each port, but the picture you posted appears to have some what normal looking injector at each port.

dimented24x7

iTrader: (2)

Id use at least a solid 1/2" thick aluminum plate for the top lid. Maybe thicker. There will be upwards of 1800 lbs per square foot. Basically at idle and decel, youll have the weight of a small car pressing on the plate.

Also, what method will you be using to drive the extra set of injectors?

jwscab

that set up shown is a later version from GM to replace faulty poppet valves. It was available for a short time, and now if you need replacement injectors, you can buy this kit from the aftermarket I think. The original's did have a remote poppet valve with the injectors located in the center.

are you planning to plug the injector holes?

kdrolt

length = (4.0" bore * 4) + (1.0" gap * 3) = 19"
width = ( 12" guess width side-to-side ) = 12"
area = 228 sq inches

At idle, with worst-case perfect vacuum inside the intake and 14.7 psi on the engine exterior, the net downward force pressure*area, or 14.7*228 = 3351 lbs

So I differ by approx 2x compared to dimented24x7's number... but it doesn't matter because he's right: that's a significant force and the worst-case loading will be at idle.

I don't worry so much about permanent metal deformation on the cover plate but I do worry about air leaks where the top/sides meet the lower intake. So you might need several vertical stiffener columns inside the plenum.

The CFI people will be all over this if you can get it perfected.

EDIT: it occurred to me in looking at the lower intake shown, that once you get a plenum installed above it, that it should run similarly to a Superram intake, albeit with slightly shorter-length runners. IOW when you look trend-wise at Superram type dyno plots, that you should get something very similar.

e.g. like the Super ram results here: https://www.thirdgen.org/forums/tpi/...feb-super.html

A CFI manifold is really a TPI that lacks port injection and has enclosed acoustically-tuned equal-length runners fed from a common plenum, so the dyno performance of a CFI will behave like TPI.

dimented24x7

iTrader: (2)

I dont think youd have to, correct? Theyre within the plenum, so you could leave them open and get a little extra flow...

jwscab

yeah, i was just curious.....the crossfire guys have done a bunch of testing trying to 'share' runners by opening up areas due to the tiny cross section with mixed results. These injector holes are similar, and since this is wet flow, I wasn't sure if there would be detrimental effect to having the hole there....

I would think something more like 1/4" or 3/8" top plate would be sufficient, particularly if there are supports. The original crossfire lid and other lids (offy) are around 1/4" to 3/8". certainly stronger than the thermoplastic the orginal lid is contructed of (and throttle blades, for that matter.)

great project....should be a screamer!

Tom 400 CFI

Cool.

This was talked about at length on the Crossfire forums almost 4 years ago.

I'm glad that someone is finally trying it out!

I second the motion to use an aluminum spacer. I made a 1/2" spacer on my old CFI Trans Am out of Corian. It didn't last at all. I was asking way too much of a material that was too weak. Plus look at the distacne between lid bolts on the vortec manifold, vs the distance on the CFI lid bolts. I think you'll suck in the sides of a phonelic spacer on that intake. Just my .02

-Tom

liquidh8

This is going to be pretty cool fast! I'm gonna follow this set-up. I've been tossing the idea of a dual tbi set-up for my vortec heads. It was either get a holley 4 bbl tbi, or run dual tbi's.

What's nice about sharing the plenum area is you could twin turbo it, running a hat to each. I saw a setup like that in a rustang mag a few months ago, albeit they used 2 radix centrifical on it.

BMmonteSS

I don't want to sound anti-TBI, but why not just stick with the multi-port injectors? If you can some how retrofit standard multi-port injectors into this manifold, you might as well. The runners look to be very strait and rather large, with a big enough plenum this could be the ultimate junk yard FI setup. You could do a flat plate and then use 2 or 3 2-barrel TB's without the injector pods to feed it.

If the system works as it appears, the retro-fit setup pictured just has some flexible lines feeding each of the injectors and the wires exit the plenum along with the fuel lines. From the factory the upper plunum has the diverter valve along with some other junk for the longer runners, if you could gut the factory plastic plenum cover you would have one very large plenum and you could even use the stock TB to feed it.

It just appears to be a LOT of space for fuel to puddle if you used this as a wet flow intake. Fuel puddling is bad enough with the carb intakes we've been using, I couldn't imagine how bad it would be with this much surface area and how slow the air would be moving with this monsterous plenum.

1982TA

iTrader: (1)

any updates on this at all...I have been thinking of going CFI for a while now, but this has me interested.