i decided to convert back to tbi from carb and i need some opinions from you holley 670 people...
i have spent the greater part of the day researching this board and holleys web site... i have not found all my answers. i have alot of mods and i plan on doing more but my carb is running toooo rich. i swapped carbs with a buddy and it still runs a little rich! i pulls much harder then the stock tbi unit did, but i have ordered the holley unit.
1. how do you plug in your fuel injector wires to the delphi injectors? from the pic it looked like a flat 4 plug wire.
2. i have read problems with the iac. the pic in the jegs looks like it has the iac on it. i have heard both theres came with it and also some didnot come with it. is this a hit or miss thing? also pablo was saying something about running upwards of 30 psi on the injectors, i thought the stock fpr only went to around 14 or 15?. if it needs that much pressure then i will have to forgo my origional plan.
i was going to use the mallory 4309 that is already in there. i was going to loosen the diapragm in the tbi unit and plug the return fuel line and use the mallroy one so i would only need to hook up 1 fuel line the mallory is adjustible from 2-13 psi and it has a built in vaccum port so that should help a little. does anyone see any problem with doing this?
also it says it will bolt up to the stock manifold how do those 2 inch throttle plates open. does it come with some type of spacer?
i had planned on possibly using the squarebor to quadrajet open spacer under the adapter this will allow the engine to pull from both sides of the tb instead of just one. i think the spacer is a half inch... i'll have to go look.
well let me know if i am an idiot or not.

 

If the mallory unit isn't a return type regulator. Dead heading the fuel pump is not a good idea. Either the regulator won't hold back the 100 plus psi the pump will be making or you'll burn up the pump because it's just trying to push fuel against a wall. As for the holley unit, there are some issues with the connector for the iac, it takes a truck style connector I believe, I don't believe the injectors are different. Also the throttle cable is different.

As for running 30 psi. This is what you have to do if you want to make serious HP with TBI. Feeding your engine above 300 hp takes some finese. You'll need the 90 pph injectors and at least 15 psi. I'm running 75 pph with 22 psi, I'm feading about 320 hp. All this is dependent on one HUGE factor. CHIP TUNING. You won't even get your car to idle correctly with this TB and bigger injectors without chip tuning. There are some guys who do the mail order chip tuning thing, it's pretty much point less other than doing some minor changes like removing speed limiters and making ruff changes to the fuel and timing curves. Kinda like telling some one what jet to put in their car over the phone without ever seeing the car. If you're not planning on getting into chip tuning then you need to learn how to tune your carb. You won't ever be happy with the tbi unless YOU can control it.

 

i guess you did not read my sig... the mallory 4309 has a return on it. also i have used a chip from tbichips.com for some time i had it on the car for about 2 years b4 i put on the carb and it improved my performance greatly also i have the winaldl program i just need to get a burner. also the injectors on the holley are diffrent they are made by delphi not gm and if you look at the pic the plug for the fuel injectors plug into the base of the tb not directly on the injectors. also i know it needs the truck plugs as i said i got them in the junk yard today they were a whole dollar... also i am going to run the injectors that come with it it is made for the 5.o liter truck.
thanks for your input.

 

Unless you have heads and a cam I would not consider the 670 yet. Get used to chip burning first. It will make things easier for you later when it comes time for the 670.

 

ok like i said i have a carb on there and i am not going to go to the junk yard and buy a used tbi when i can order the holley unit. i think it will be fine and i do have the lt1 cam (sig)
its getting close to winter time and i don't want to sit for 10 mins for the car to warm up also i beleive pablo is running his with the stock heads??? oh and i ordered the 670 last week so its too late.
i don't know if anyone has noticed but the intake ports on the lo3 heads are very tall. i lined up 2 difffrent sets of gaskets on there and if they were to be ported there would be a minumun amount to gasket match it. i am not saying i am going to but they were perfectly lined up with the gaskets.

 

The LO3 ports are standard size. Where they fall behind in the game of performance is the amount of material that surrounds the pushrod slots as well as the swirl ports. This equals small and crowded runner sizes. Even though you have the LT1 cam I would not put on the 670 unit yet. You have not maxed out the stocker yet. You could use the Holley unit but I would use your stock injectors. Be prepared for a lot of tuning with a 2" TBI.

 

venturi velocity helps keep fuel atomized. too big a venturi will result in poor throttle response. i think my 2.00 inch TB is a bit too large for my 350 cid in current tune. my new cam install may be a better match for the big(?) 2 inch.