Inline 6 Blow through Turbo help

[the idiocracy]

Okay, so here is the background

1967 C10, Longbed, Stepside, original inline 6 (250ci) in it. I decided to do a blowthrough turbo setup instead of putting in a SBC or doing an LS swap. Everything is in and its running (I'm friggin amazed...I don't know crap about turbo carb setups...its been a learning experience for sure). My issue now is fuel. I disconnected the lines from the stock mechanical fuel pump and put an external electric pump and a boost referrenced fuel pressure regulator inline. The reason for this is that the fuel pump needs to supply fuel about the boost pressure and the mechanical pump can't do that.

Here are the specs on the pump that I am using...

Brand:Trick Flow Specialties
Part Type:Fuel Pumps, Electric External
Product Line:Trick Flow® High-Flow Electric Fuel Pumps
Summit Racing Part Number:TFS-25004P

Free Flow Rate: 43 gph
Maximum Pressure (psi): 45 psi
Inlet Size: 5/16 in.
Inlet Attachment: Hose barb
Outlet Size: 5/16 in.
Outlet Attachment: Hose barb

https://www.summitracing.com/parts/tfs-25004p

The problem that I am having is that something is causing it to not provide constant pressure. I am trying to upload a video to show what happens. The pump doesn't make a consistent hum, it sounds like its straining and then it ...nevermind, let me see if I can upload this damn video. Its 2:30ish, so its kinda long, but I videoed the entire engine bay, everything I could get so and carb turbo experts can look over the setup and identify anything that I have done incorrectly.

https://www.youtube.com/watch?v=HTvlf80lA74


I know there is wiring and vacuum lines everywhere...that will all get cleaned up. I appreciate any insight anyone has.

I am thinking that the pump is trying to pull fuel at a rate so that it can supply fuel at 43psi. The fuel lines are 5/16" from the tank to the pump, so I'm not sure if that is sufficient to supply fuel for what the pump is trying to do. Additionally, the regulator is bringing that 45 psi down to 5ish at idle (not under boost).

Is it possible that the pump pulling too hard and the fuel lines can't support it? I popped the gas cap off to make sure the tank isn't vapor locking, so thats not it.

I should also note that the regulator is a Non-Return style. This one...
https://www.summitracing.com/parts/sum-g3032b/overview/

Im at a loss here.

['68OrangeSunshine]

Well Kid, You're WAY ahead of me in L6 Technology. I'm still running the XXth Century style 292 at .030, w/Clifford headers, Offy intake, Edelbrock 1404, 4 bbl 500 CFM, Crane 260H cam, SM465, Centerforce clutch, 12 Bolt 3.73 Eaton posi rear. I had a Pertronix II set-up, but it killed itself above 3000 RPM [60-65 MPH] so I went back to a DelcoRemy Point-triggered distributor. Now It runs great.
It's my second build, but then I get about 25 years to the engine, so some things [like skills] get rusty.

Can I presume you are familiar with the websites listed below? --
www.inliners.org
www.stoveboltengineco.com
www.cliffordperformance.net
www.12Bolt.com
To get to basics, it sounds like you have a fuel flow problem.
Are there any long stretches of rubber fuel line in your system? How many filters? Does the tank have a fuel return system you could be using?
You might have to bump up to Dash-6AN lines all the way thru. With that kind of fuel requirement you're in SBC 5 Liter [301 CI] territory. The OEM 5/16" fuel lines may be restrictive.

[the idiocracy]

Thanks man. And yes, I'm familiar with those sites. I'm starting to agree with you, I think I may be pulling harder than the lines can support. No long runs, 2 sections of 5/16 rubber, each about 8" in length.

I don't know about the vented tank, but I am also thinking that I need to go to a return style regulator, which means I will have to plumb in a return line. And if I'm doing that, I'll go to 3/8" supply as well.

[The Chainsaw]

95% of electric fuel pumps are not made to "pull" fuel from the tank. Some can do it with decent reliability, (myself included) if they are close to the tank, but it is not recommended by most.

I'm surprised it is even getting fuel period where you have the pump mounted! That is a very long run with a huge uphill before the pump even sees fuel. Mount that sucker under the cab as close as you can get to the tank and it will be much happier.

Even better would be to find someone to weld a fitting to the bottom of your tank so the fuel pump doesn't have to pull fuel uphill at all.

I wouldn't change the fuel line size until trying to relocate the pump. That little fuel line can support more power than most people think.

Sweet build by the way! I always wondered how well a turbo'd straight 6 chevy would tow

[Overdriven]

Definitely mount the pump closer to the tank. Under the cab on the frame rail should be fine and make sure the feed line isn't collapsing.

I'm not an expert in fuel pumps but I'd think that the pump would be better off with a return style regulator. Without a return the fuel isn't moving much and the pressure is just building up while the pump is still trying to move fuel. This is likely causing cavitation in the pump, straining the pump and heating the fuel. With a return fuel will be flowing back to the tank so fuel after the pump will be moving lessening strain on the pump, lessening cavitation and heating the fuel less. Modern returnless fuel systems slow down the pump in low demand situations for these reasons.

[the idiocracy]

Noted guys, thanks. I will relocate the pump and see how that works.

Regarding the regulator, the one that I have is a non return style, but it has a second OUT port that is capped off. If I was to plumb that as a return, would that work, or would I simply loose all pressure due to the fuel taking the path of least resistance?

[Overdriven]

Originally Posted by the idiocracy

Regarding the regulator, the one that I have is a non return style, but it has a second OUT port that is capped off. If I was to plumb that as a return, would that work, or would I simply loose all pressure due to the fuel taking the path of least resistance?

It's a single regulator, the output is just split like a y-pipe. So yes you'd lose all pressure if you used the the 2nd port as a return. I'd try relocating the pump and see what happens. My logic is sound but I could be wrong and it may not apply here.

[Mrturner1]

Now that is a cool engine! I'm not a big L6 enthusiast and I doubt I'll ever own one, but that setup just looks flat out awesome. I bet that thing makes a tone of torque. Cool idea and cool truck man!

PS that turbo spool sounds exactly like a Cummins lol

[CST10]

Nice set up.

[Orange Crate]

If you don't want to run a return line back to the tank, you can use a Nissan pump from a 280Z. I don't know what pressure you are running, I assume pretty low since it is a carb but here is one for FI type pressures:

http://www.rockauto.com/en/moreinfo....014&cc=1209293

[the idiocracy]

Thanks guys.

Orange Crate, whats the barbed fitting on what I am assuming is the inlet side for? That pump is very similar to what I have sans that barbed fitting.

Never mind, thats an outlet too. and the PSIs are too high. Minimum is 70 psi. That would just strain the regulator.

I am going to move the pump to the frame rail right underneath the tank this week, so there is no "pull" necessary and see how that goes. Hopefully that is the problem. I only mounted the pump where I did for simplicity in the startup process, so I would have everything that I changed right there in front of me on first start up and could see any problems immediately. I didn't think that it would actually cause an issue. Hopefully its a simple fix.

[Orange Crate]

I was guessing that the pressure would be too high. To answer your question the barbed fitting is the return (back into the outlet stream). You don't have to run a return line back to the tank. Maybe it will help someone else that is running higher fuel pressure than you, or maybe when you change over to FI?

[dirtyjim]

you will need to run a return style regulator with that pump. you will also need at least a 3/8 return line.

[The Chainsaw]

Didn't see the regulator setup you have. I would definitely get a return style regulator.

['68OrangeSunshine]

I used to run a Holley Red electric fuel pump on my '67 K/10 Suburban w/454 V8. It was mounted on the pass side frame rail, about under the cab [the tank was in stock location, behind the rear axle].

[scooterpimp]

Keep us posted on your progress , my L6 keeps asking for a turbo....

[mike16]

I was guessing the waste gate. but 5/16th fuel ine is pretty small. what ever else you do to the fuel system a larger diameter fuel lne is a must.