Mods, I wasn't sure where to put this so if it needs to be moved thats cool. Maybe we need a fuel system sub-forum?

Anyway..

My car (86 iroc LG4) originally had the CCC, I now have a speed demon, however I'm going to go to fuel injection. My tank will be sumped and I was planning on running an external electric fuel pump along with new fuel lines. My main question is what to do about the return, specifically the old sending unit on the tank. My plan was to somehow cap off all the lines and maybe replace the return one with something? I'm hoping to get some suggestions.
The attached pics show what it is now. 4 lines, supply, return, evap, and one that ends outside the tank with some sort of cap/vent thing.
What I have in mind is using a -6an line for the return line then adapting it to the hard line on the tank. I don't think it would cause a bottleneck?

Suggestions/comments appreciated

Thanks

 

Thomas

There are couple of approaches you can take with your EFI system. If you plan to run a conventional full circulating EFI system you will need at least 3/8" line for supply, 5/16" for return and 1/4" for charcoal canister purge line. Newer dead head systems do not use return line. Depending on your engine appetite 3/8" maybe good enough. GN guys like to replace 3/8" supply with 1/2" to guarantee that engine never leans out. Sumping your tank will prevent fuel starvation during spirited maneuvering or you can replace your old tank with FI version and go to in tank FP.

//RF

 

depends on the usage. if it's street then you can just reuse the old sending unit and put in a bigger pump. i would always suggest a loop system though. if it's a racing car then you need either a sump or foam inside the tank.

 

Yea, its going to be fairly stout system when I'm done. I have a -10 leading into 2 fuel pumps (1 will be hooked to a hobbs switch reading the supercharger pressure...) then to a -8 line, fuel rails, regulator, then -6 line back to the tank. I was considering just mating the -6 with the stock 5/16 hardline out of the stock sending unit. After some research I found that -6 ID is .34375 and the 5/16 hardline ID is .2565 (Assuming a 0.028" wall thickness). If I adapt these two would I create a bottleneck? the 5/16 line would only be like 5-6" maybe less at the tank. Thoughts?
Also, what have people done to cap off the unused hard lines?

 

Thomas

You can cap unused outlets.
You can also get a different sending unit that only has three outlets. For an engine with a healthy appetite I would replace 3/8" intake hard line with -8 AN Fuel Pickup & Return Kit from Jaz Products 835-008-11 by removing original feed through line and enlarging hole to a proper size. You may want to contact Jaz Products to get more information.
http://www.jazproducts.com/AN_fittings.html

IMHO, unless you are running close to 750 HP and above going to -10 AN is a bit of overkill. For an average street car -6 (OD 3/8") is adequate, and -8 (OD 1/2") with a high volume pump is good for most street/strip cars. When working with soft steel tubing use a proper bender to avoid kinks and necking. Also, I would make sure that my supply line is restriction free - no 3/8" or 5/16" neck downs. Avoid using 90 degree elbows whenever practical. Just my 2 cents - I hope this helps.

//RF

 

the -10 is only to make sure the fuel pumps have enough fuel. They are going to be close to the tank as well. -8 AN suppply and -6 AN return, thats what I'm planning. I'm hoping for 500 rwhp with the blower, first things first. I'm using braided line, not tubing.

I'm just not sure how to modify the sending unit. I'd like to keep the stock float for the fuel gauge.
How would you suggest capping off the unused hardlines?

Thanks.

 

Thomas

Since this is a highly modded fuel system braided line is fine - a bit on expensive side, but that's what I did in my fuel system as well. Summit has good deals on braided lines and AN connectors are OK. If you can find a three port sending unit (I think early 80's Camaros had three port units) use it in place of your 4 port. Leave stock 3/8" line in place as it will be used strictly to support fuel level sending unit and sock. Drill a hole to accommodate 1/2" feed through for -8 AN supply line. For return line you may have to dremel out 1/4" vapor return line completely and install -6 AN feed through bulkhead. I you may want to experiment first, since space is at a premium..
To cap a line I would cut off beaded end and use a double flared line cap and use a standard plug to cap. It is a bit of work. Do not use rubber caps as they tend to disintegrate over time.

//RF

 

kinda in a predicament...I have the same pump in my tank that the OP has, but mine is already FI. its an '87 trans am with the 305 TPI. folks have told me that my fuel pump for that year should only have 3 lines running out of it. could this be a reason for my engine shuddering sometimes? should I switch it with a basic pump most auto stores have listed for my car? thanks in advance