Quote: Originally posted by Dominic Sorresso wdigitog, If you wanted to do that, I'd suggest going with a VAFPR. Tom 400CFI has done that successfully from what I've read. That way you increase pressure when its needed. As you get beyond 270hp or so, you'll need to invest in larger injectors anyway. Some one say my name? I agree with Dom about the hp limit with stock injectors, though I would have pegged the practical limit closer to 250 hp. I do have the VRFPR, and it works superb for my combo. It is set so that at idle, I have 10 psi. At WOT I have about 14 psi, and for with my combo, my engine likes it.

cool sounding ride tom..454 injectors hm?..didn't know MSD made them thanks...did you dyno your package yet? probably has tons of bottom torque! so i guess these 75# injectors really outflow the stock 60#'s eh?..what happened without the VAFPR? could you run this setup with 12lb FP constantly? stan

I haven't dynoe'd it yet, but I estimate the power to be around 315 - 320 hp. I figure this by by 13.25 1/4 mile time @105 mph. That is right in the middle of LS1 ss territory. And yes, it does have a TON of low end torque! Too much IMO. It is all done by 5000 RPM; shifting later than that is nothing but a waist of gas. I would preffer to move the power band up; I would like a much bigger 3000-5500 RPM band, and less at 1200. I can't launch above 1200 -even with a tire warm up/clean off- or they go up in smoke. An Offy cross ram intake, like the one Joby talked about above, would be a gigantic improvement to my combo. My 400 is choked with that ported, stock intake.

Before I had the VRFPR, my engine had driveablity issues. I would get the most hp with the pressure set at 14 psi; I would run the best 1/4 mi times. But the car would idle rich, and sometimes stall when I pushed in the clutch, coming to a stop. It would then be flooded, and I would have to floor it to clear it and get it to re-start. Very annoying in the middle of an intersection! If I lowered the FP to around 11 psi, it would idle much smoother, and not stall, but then it just lacked power; 1/4 mile times would suffer. The VRFPR allowed my combo to have the best of both worlds. It NEVER stalls now, and runs very well. I even turn 24+ mpg on the highway, which exceeded my expectations for a 400. Now for an Offy and some AFR 190 heads......

Tom,

Given the displacement of your motor, I would think a bigger manifold would provide an improvement.

how does a modified CFI manifold compare flowise with, say an edelbrock performer? is it comparable to the point that equal HP wouldn't be a problem? stan

No. The STOCK CFI manifold flows air very poorly. IIRC, it is along the lines of 144 cfm/runner. That's terrible. But that is also totally stock. Now we know from seeing many people, such as myself, Dom, and several others that a stock PORTED CFI intake will support well over 300 hp. It seems as though 350 hp is the absolute limit. At that point the intake in very much, the biggest restriction.

I feel that on my particular engine, a swap to a Performer RPM and 750 carb would get me at LEAST 30 hp, and put me in the 12's. But I also feel that an Offy would do the same thing, for about the same money, and I'd still have EFI.

So I think that the CFI system has the POTENTIAL to keep someone happy up to over 400+ hp; first port the stocker. then get an Offy as you build.

I have the Offenhauser working now. I am still not finished but I have to go to the yearly emissions / safety check soon, so I bolted everything together for that.

( Click pictures to enlarge )

I had to do some minor grinding to clear the oil pressure sender.

I wanted to be able to use the stock air-cleaner. To get the throttle plates further apart to match the Offenhauser I decided to rotate the front TBI. To do that I had to modify it to clear the air-claener base and also modify it so I could insert the throttle shaft from the other side.

( Click pictures to enlarge )

I made a custom lid and installed my modified swirl-plates.

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I re-used all cable brackets and got the fuel system back together.

To clear the distributor I had to remove a clamp on the air-cleaner base for the vacuum hose.

( Click pictures to enlarge )



The stock air-cleaner is in place. You could probably fool almost anyone that it is a 'stock' cross-fire with that air-cleaner in place. And YES!!! It is does clear the hood.





And finally a short video of idle with some stomping on the throttle. It idles perfectly and the throttle response seems to be just as good as stock. The sound on the movie is not very good.



The engine has stock pistons.
AFR 190 heads.
CompCams 12-402-04 ( 114, 212/218, 0.444/0.444 )
Roller tip rockers.
Offenhauser Cross-Ram with custom lid.
Hooker Super Comp headers and dual exhaust with X-pipe.
All emissions stuff removed.

I am still using non bored TBI's with stock injectors, stock ECM with stock chip.

When the emissions/safety check is done I will do some more modifications.

* Install larger injectors
* Run the injectors in paralell with external fuel pressure regulator.
* Possibly bore the TBI's to 2"
* install 7747 and start tuning
* Install the supercharger.

very cool, keep us posted

Looking good, looking real good. Will you be able to dyno the car without the SC on? I'd recommend tuning the eprom first N/a then going with boast.

NICE work Jonas! Very nice work. Man, I'm jealous now.

It is very easy for me to switch between supercharged and NA. It is just a one minute job to change to a shorter belt.

I will start tuning N/A and then with the supercharger. I don't have access to a dyno near by, but I will use street-dyno to get comparable hp/tq figures.

From the results so far I see that the Offenhauser port size will not create any driveability problems when using TBI instead of carbs. Idle and throttle response is good with the stock Cross-Fire chip. The stock chip is way lean with engine load because of the increased air flow at low vaccum, but larger injectors, a vacuum referenced fuel pressure regulator and some tuning will fix that.

sorry for reviving this old thread from the grave

but are there any updates ?