[SteveDeluxe300]

Hi Guys
Im running a Holley black electronic fuel pump and a 100 micron pre filter. I'm also using a holley fuel regulator and AN8 fuel lines and a Robmc sending unit from my stcok 1969 tank. Ive capped off the two rubber breather lines from the tank with rubber hose and end plugs.
Here's the rub, I can't seem to maintain a consistant fuel pressure to the regularoe. I set it to 8 psi like holley reccomends but after I hit it a wot it'll be at 3psi when I stop or 6 or 2 Im perplexed. Anyone have any ideas? Thanks fpr your help.
Steve

 

[pannetron]

The tank needs a breather.

 

[Geo71]

Have a return line?

 

[SteveDeluxe300]

The tank needs a breather.

Thank you

 

[SteveDeluxe300]

Have a return line?

no

 

[DUTCH MAX HEADWORK]

Do a search on this site for 1969 fuel vent. I would do it but I'm on my telephone and I'm not to phone savvy to post a link

 

[pockets]

Put a vented/locking gas cap on it.

 

[hydro462]

Get a fuel filter 3/8" and connect it to one of the ports. Put a loop in the hose and mount the filter as high as possible..

 

[Hotwire]

As everyone said above, you're pulling vacuum with the tank sealed as it is. After wot and the pressure is low, have someone open the gas cap while you watch the pressure gauge, should go back to normal.

 

[SteveDeluxe300]

I purchased a one way valve and am going to install it on the 3/8 line from the tank and zip tie it above the axle. I'm hopeful that will resolve the pressure problem. Thank you all for you help and input. I appreciate it.

 

[69SS454]

I purchased a one way valve and am going to install it on the 3/8 line from the tank and zip tie it above the axle. I'm hopeful that will resolve the pressure problem. Thank you all for you help and input. I appreciate it.

I would not install a check valve on the vent line. The tank needs to breathe in and out. You also need to run a vent hose to the smaller line. The two lines are in opposite corners of the tank incase your car is not sitting level.

 

[70GS455]

To test, just leave the cap off and try it

Sent from my SM-T817V using Tapatalk

 

[68Chevele]

Hi Guys
Im running a Holley black electronic fuel pump and a 100 micron pre filter. I'm also using a holley fuel regulator and AN8 fuel lines and a Robmc sending unit from my stcok 1969 tank. Ive capped off the two rubber breather lines from the tank with rubber hose and end plugs.
Here's the rub, I can't seem to maintain a consistant fuel pressure to the regularoe. I set it to 8 psi like holley reccomends but after I hit it a wot it'll be at 3psi when I stop or 6 or 2 Im perplexed. Anyone have any ideas? Thanks fpr your help.
Steve

Last time I had that happen the fuel filter was plugged and after only used for a few years at the track only how can that be? changed the filter 6pis all the way down the track. What brand of regulator are you using, all my issues ended when I put in an Arrowmotive one.

 

[SteveDeluxe300]

I'm running a Holley 12-840 Fuel Regulater. Upon further consideration I'll run the smaller breather line up to above the axle also and zip tie it in place.

 

[DUTCH MAX HEADWORK]

I'm running a Holley 12-840 Fuel Regulater. Upon further consideration I'll run the smaller breather line up to above the axle also and zip tie it in place.

Run both up. That way if one is exposed to liquid fuel and the other is plugged fuel will not be forced out of the vent if the tank is pressurized.

Run both of those hoses to the outrageously expensive reproduction plastic combiner 1969 FUEL TANK VENT or this filter WIX FILTER mounted vertically as high as possible with the 2 inlets at the bottom and single out the top. Take a fuel line off the single tube at top and run it as high as possible the loop it down along or through the frame rail out the back near the rear bumper. Place a small piece of lawnmower air filter in the end of the hose to keep dirt and critters out. LAWNMOWER AIR FILTER.

This is what the inside of your tank looks like and where the vent tubes lead. By using the 2 vent tubes, one is always open and the surge valve or filter above are there to allow any surge to return through the open line. At least that's the idea.

Don't overfill your tank. Once the fuel nozzle kicks off, she's full.

 

[SteveDeluxe300]

Great post.thank you.

 

[Aaron]

Call Holley and RobbMc and make sure you have things plumbed to matches there specifications.

What is the WOT scenario that your experiencing this issue. Just a stab of the throttle or from a dead standstill?

Why would you plug the vents?

 

[SteveDeluxe300]

Thanks Dutch
I went with the wix filter method you suggested, It looks great i hooked it all up today. Seems good so far.
Thanks again for the input.