I'm strongly considering moving to EFI with my ride as its more in my comfort zone than carbs.
I've been eyeing several systems. TPI setups look nice but are limited to lower RPMs. I really like electromotive sbc kits but they are just too pricey for me at this time.
I've about narrowed it down to Holley's TBI programmable KIT (http://www.holley.com/HiOctn/ProdLine/Products/C950/C950TB/950-24S.html)
Ive also had some conversations about a multiport kit fromTHESE GUYS (http://www.affordable-fuel-injection.com/fuel-injected-specials.htm)

I'm wondering about what you guys with fuel injected cars did about the return system. My 68 was a 307 car originally and I "think" the feed line is 5\16. Is this large enough for either of the above systems. Is there any reason I couldn't use the vent line on the factory tank for my return line? Also any other sytems out there that might be a better choice. My car is a weekend cruiser and rarely if ever will see a track.
Current combo is
383
chevy "hot cam"
peformer RPM heads and intake
700R4
3:73

Any input appreciated.

I am going to be doing a blown BB with these guys.

http://force-efi.com/

Tom

Dude I will never go back to a carb. The driveablility of the 540 has doubled since EFI. I will put a nasty procharger on top of that shortly and keep you guys posted.... Stay tuned

For $1500 that looks like a cheap setup. Looks like a Holley EFI intake and rails, stock 2 bbl tbi for an airvalve and factory computer. Also cheap fuel pump.

I'd want something with a programmable ECU.

Originally posted by Kx69:
I am going to be doing a blown BB with these guys.

http://force-efi.com/

Tom Quality stuff but closer to the price of the electromoitive stuff (http://www.electromotive-inc.com/mpi_kits.html)
more than I can go right now.


Originally posted by Doug F.:
I'd want something with a programmable ECU. The Holley guy graemlins/hurray.gif I was hoping you would chime in. Does the holley support datalogging in some manner? Also If I were to go this route what might I need to do for a reliable supply
\return system.

The current software has a PC datalogger. Starting 1/1/04 the new units will have new software that will support wide band O2 and have an internal datalogger. Very nice stuff capable of controlling very high HP engines.

The TBI kits come with a nice 255 LPH fuel pump and filters. You just need to run a 3/8 supply and 5/16 or better yet a 3/8 return.

My own car has a pieced together system that costs reasonable and works very well. You could probably do it for $1500 with some ebay shopping.

You'll have to make a return line in the tank. The return must go all the way into the tank and exit within an inch of the bottom. If you used the vent line the fuel would simply fall from the top of the tank. This can build up static electricity, which is something you definately dont want to discharge inside a gas tank.

Wideband operation would definitely be nice. Do you happen to know if the part numbers for those 04 kits will change and where the price might go? I'm looking at the 950-24S. $ 1500 is about my range.

Originally posted by chevymad:
You'll have to make a return line in the tank. The return must go all the way into the tank and exit within an inch of the bottom. If you used the vent line the fuel would simply fall from the top of the tank. This can build up static electricity, which is something you definately dont want to discharge inside a gas tank. Hummm...I wouldn't have thought that..I guess I can always pull the sending unit and add another line in....If I go to that much trouble I might as well add a pipe with some holes in the tank and run an intake pump...
Thanks for the replys...
Jack

Return lines should empty into the top of the tank. Otherwise you can cavitate the fuel and cause backpressure to the return. Haven't heard that about the static electicity before? The tank should be grounded.

the static electricity sounds like an old wive's tale. the return line is connected to a fitting on the tank which is grounded. doug is right about causing cavitation. the pump would suck up bubbles from the return. tom

Would a vent hole work ok*as a return fitting with a flexible hose clamped on or should a threaded-type fitting be placed on the tank?

Ryan

A COUPLE OF THINGS, THE RETURN NEEDS TO GO TO THE BOTTOM OF THE TANK FOR SURE, YOU DO NOT WANT FUEL
SPRAYING AROUND THE TANK WHEN THE LEVEL GETS LOW,
THE HOLLEY TBI IS ALSO GOING TO BE A LOWER RPM UNIT, VERY STRONG IN THE LOWER TO MID RANGE BUT FALLS OFF AT THE UPPER RANGE, MUCH AS A TPI, TPI'S ARE VERY STRONG IN THE SAME BAND, WITH THE STEALTH RAM INTAKE AND RAILS THAT ADDS ABOUT 1500
RPM RANGE TO A SMALL BLOCK, I HAVE WORKED ON TPI
SWAPS AND THE 87 AND EARLIER UNITS ARE VERY FORGIVING AS FAR AS COMPUTER VEHICLES CAN BE, HOPE THIS HELPS,ROB...

Well now I'm confused regarding the return line as in whether I can use the vent line. It obviously comes in from the top on my tank. I dont
know how far down the tube goes in the tank. Seems to be differing opinions here.

I do know that the early TPI's use MAF sensors instead of a vacuum calculation. I might have consider TPI with short runners. I don't guess I understand why the holley throttle body would be similar to TPI.
Jack

I think since Doug F is a Holley EFI engineer, his opinion carries a lot of weight. If he says it's okay to dump at the top of the tank I'd go with it. The only thing I'd check is to make sure the vent line is at least 5/16" diameter (a lot of them are 1/4") and that there isn't any weird baffling/venting inside the tank that would obstruct the flow of fuel back into the tank.

Jody

Been running mine through a vent line for 10 years with no problems, don't know what else to say.

Changed many stock efi fuel pumps... The return lines all empty at the bottom of the tank.


Edit: That said I havent been able to find a single source to back up that it should exit near the bottom. I know i've read it before in more than one location. However, I have found a couple of sources saying it should go in the top of tank.. both sources were mag articles. :confused:

Anyway, if I find anything I'll repost it.

Originally posted by chevymad:
Changed many stock efi fuel pumps... The return lines all empty at the bottom of the tank.


Edit: That said I havent been able to find a single source to back up that it should exit near the bottom. I know i've read it before in more than one location. However, I have found a couple of sources saying it should go in the top of tank.. both sources were mag articles. :confused:

Anyway, if I find anything I'll repost it. I've done it both ways without issue. I have also read that returning it below fuel level causes less fuel aeration. I was just saying that I like to think an expert (Doug F) has a pretty good handle on it. I think either way seems to work, just make sure the line is the proper size.


Jody

Well, after much searching the only thing I found to back me up is edelbrocks efi installation instructions. They give 3 methods of installing a return line into a tank; rubber hose in tank, bulkhead then hose, and hard line. Both hose methods they say to use at least 4" of hose inside the tank. The diagram for the hardline shoes the line exiting next to the pickup but with a kink in it aimed away from the inlet. They do say with all 3 methods to aim the return away from the pickup to prevent aeration. They do not explain why you need to extend the return at least 4" into the tank however.

I beleive I read the static discharge theory in a trade mag at work, not a normal car mag. By searching the web however I find many many people getting by, by just dumpin the fuel in the top. Whether thats luck or not, who knows.

If you do use the vent for the return, what are you going to do for a vent?? Just something to think bout.

I've done it both ways without issue. I have also read that returning it below fuel level causes less fuel aeration. I was just saying that I like to think an expert (Doug F) has a pretty good handle on it. I think either way seems to work, just make sure the line is the proper size.
I dont doubt he knows what he's doing. Just know what i've seen/read and trying to pass it along. Hate to have somebody blow up a rig because of something nobody's heard of. Especially if tank mods are going to have to be done anyway, might as well play it safe.

"If you do use the vent for the return, what are you going to do for a vent?? Just something to think bout."

Exactly. But, I think Jack's car is a 68 or 69, he might be running a vented cap. Some things never change, there's got to be a vent somewhere.

Jack, I think you're going to need a 3/8" feed and 5/16" return. You definately don't want to running something outside of what the ECM is set up to expect. It makes assumptions about this stuff. Why not use the existing 5/16" line for a return, fab up a 3/8" feed line, keep the vent? You'll need a big block sending unit, or hack up the 307 sender.

Tom

(and Doug is the real deal expert)

I should have clarified, I used one of the inlets for what I guess you would call the vapor canister on my 72. If all you have is one vent line and a non-vented cap you certainly would not want to remove it. I have a vented cap also.

As far as I'm concerned it should work ok with anything that has been mentioned. The pressure backup in the return line will be minimal.

What I can tell you for sure are bad things to do are:

Not run a proper inlet filter (60-100 micron) and high pressure after the pump filter (10 micron). Injectors or pump can be damaged.

Use restrictive fittings such as some poor banjo fittings I've seen. You will have a WOT pressure drop.

Don't use big enough fuel pump or wire it with too small of wire.

Don't run the proper size injectors.

With a MPFI application don't put a sump in or some baffling.


I've learned more by my own personal work just like everyone else and learn everyday.

Some things are sensitive and some aren't. I wouldn't get hung up on where you make the return line enter the tank.

Originally posted by Tom Mobley:
"If you do use the vent for the return, what are you going to do for a vent?? Just something to think bout."

Exactly. But, I think Jack's car is a 68 or 69, he might be running a vented cap. Some things never change, there's got to be a vent somewhere.

Jack, I think you're going to need a 3/8" feed and 5/16" return. You definately don't want to running something outside of what the ECM is set up to expect. It makes assumptions about this stuff. Why not use the existing 5/16" line for a return, fab up a 3/8" feed line, keep the vent? You'll need a big block sending unit, or hack up the 307 sender.

Tom
Pretty much what I came up with.. run a new feed line and use the current one for the return...Actually my car has a non-vented cap and only 1 vent line. Im aware I need a vent in some manner. I asked about using a vented cap in another thread in the past and someone stated they had a problem finding one that would work for their tank..I was mainly in doubt about the proper sizing of the lines. I'm lazy and was hoping not to have to remove the tank again. If its becomes necesary I'll just add another line to the sending unit or in the filler neck. Looks like the Holley tbi is going to be the overall easiest route for me..
Appreciate ALL the feedback
Jack