TBI fuel routing

**Mastiff** · 01-27-2015

Hopefully this isn't too off topic, but I'm trying to get some pics or at least a clear picture in my mind of how GM routed the fuel on their TBI. The routing is sort of a hack job on my TBI conversion at the moment, with fuel hose running up the transmission brace. I understand vaguely that they went up the frame rail then to braided hose behind the engine, but I'm not clear how the hose is kept off the pipes or from flopping around in general. If anyone has pics of a factory setup, or of how they did a clean custom install, I'm very interested to see.

It's not as critical, but I'd also love to see pics of the run from the sender to the frame too. Right now I have a "service loop" of fuel line so I can get the tank down without massive frustration (and because the sender is so close to my existing hard line I couldn't make it with a straight shot), but I need to do something better. I don't like all that hose bouncing around.

This is for a K5 Blazer by the way.

**fastacton** · 01-27-2015

Sorry, no pics, but most of the stock TBI setups fun the fuel lines up the frame to the transmission area. From there it comes up above the transmission and has a clamp at the top of the bellhousing. On my '73 Blazer, I just used the factory feed and return (from the evap canister) and then routed hose from there. I even used the factory fuel sender, but I did have to remove a restrictor on the return side (I'm using an inline pump).

**Fast355** · 01-27-2015

On my 1983 G20 van I just used the tank and lines from a 1992 TBI G20 van.

**Mastiff** · 01-27-2015

The main thing I can't picture is how to get past the exhaust. In my case I have long headers, which are probably making things worse.

**brian617** · 01-27-2015

The trucks with the braided lines 88,89,90 had a bracket on the frame that supported the lines about a foot or so towards the transmission. Then they had the other bracket at bell housing bolt. The later trucks used pre-bent steel lines that only needed the bell housing bracket for support.

**Mastiff** · 01-27-2015

It might be slick to use the factory fuel lines all the way to the front, then run the fuel up the top of the motor. Could custom bend some hard lines to attach to the back of the TB and do a 180 back toward the front.

**brian617** · 01-27-2015

TBI Camaro, Caprice etc had the fuel lines to the front of the engine if my memory serves me correctly.

**Mastiff** · 01-28-2015

After looking at it, I'm really liking the idea of coming up the front of the motor. I could use my existing hard lines all the way to where the mechanical fuel pump used to be. I could run hose from the TB, but I think the slick setup would be hard line across the top of the motor and hose only between the motor and frame. I'm trying to figure out how to get from the TB to hard line. Right now I have AN6 adapters on the back. IIRC, the TB itself is tapered pipe female. Any suggestions?

**fastacton** · 01-28-2015

Ditch the AN adapters and get Dorman part numbers 800-151 and 800-153. These are "repair" lines that give you factory TBI fittings on 3/8" and 5/16" hard lines with compression fittings to connect to more hard line.

**Mastiff** · 01-28-2015

Originally Posted by fastacton

Ditch the AN adapters and get Dorman part numbers 800-151 and 800-153. These are "repair" lines that give you factory TBI fittings on 3/8" and 5/16" hard lines with compression fittings to connect to more hard line.

Thanks. Are the two numbers for in/out? Those parts look like saginaw fittings, but I could swear the throttle body had tapered pipe thread, because I overtightened one once and cracked the aluminum. What am I missing?

**fastacton** · 01-28-2015

Yep, feed and return. They are saginaw fittings which works with pretty much everything but crossfire throttle bodies. There are adapter fittings on the throttle body that look kinda like pipe thread, but actually seal with a plastic washer, those should stay on the throttle body, no need to remove them unless you're rebuilding.

**lionelhutz** · 01-28-2015

Ya, tapered pipe fittings are not the correct fittings to thread into a throttle body. The adapters used are straight thread.

I don't know what you call it besides GM steel EFI fittings, but any parts store should have repair lines with the correct ends on them. Any place I've been in has different sizes and different lengths of these lines. Here's what the end of these lines looks like. Just get the right size.

Attachment 8460

FYI, you can use a GM TBI steel body canister filter and these fittings will fit it too.

**Mastiff** · 01-28-2015

Great, thanks!

**Mastiff** · 01-28-2015

Originally Posted by lionelhutz

Ya, tapered pipe fittings are not the correct fittings to thread into a throttle body. The adapters used are straight thread.

I don't know what you call it besides GM steel EFI fittings, but any parts store should have repair lines with the correct ends on them. Any place I've been in has different sizes and different lengths of these lines. Here's what the end of these lines looks like. Just get the right size.

Attachment 8460

FYI, you can use a GM TBI steel body canister filter and these fittings will fit it too.

Missed your reply. I'm pretty sure those are called Saginaw fittings. It must be that there is a tapered insert that these go into. Actually, now that I think of it, I bet I have tapered adapters going straight to AN6 right now. I may need to find the ones that go to Saginaw...