5/16 fuel line restriction?

[Gunner1]

New problem. I just had a wide band O2 sensor and gage installed along with a vacuum gage. Car was sucking gas on the highway like a crew of sailors on liberty. Found out my neutral hot idle vacuum is 8 to 9 at 1000 rpm my in gear idle at 750 is only 3.5. I have a 4.5 power valve in it. O2 readings are 13.5 neutral and 10 in gear. Idle fuel line pressure is 6.5. In park at 3000 rpm pressure drops to 3 pounds and O2 reads 10 again new tank, new sending unit, new std vol pump, billet filter before carb. I know I need to pull the carb and filter apart and replace the power valve since it backfired and needs a lower number. Maybe a 2.5 or a 1.5. I’m thinking I might install a 3/8 line from the tank. It was a 318 car. My stock cast crank damper has rotated so I need a new one to properly set timing. Used a plug hole stop to verify. MSD no vacuum canister. Was set at 12 idle. 36 all in at 3000. Vacuums might come up with a proper timing setting. Anything I’ve missed?

 

[68-500]

Yes you need to get your timing at idle up. Minimum 20-25*. Ill bet you gain gobs of idle vacuum. It will probably fix your rich idle because the PL won’t be open at idle .

 

[BSB67]

Tell us about your cam.

 

[ckessel]

Maybe some of the hose is separating/collapsing which will cause restrictions. Also, every brass/steel fitting involved from tank to carb is a restriction. Look on the inside of them. They are not the diameter of the hose.

 

[451Mopar]

When I get a new-to-me classic car one of the first items I check is the condition of the fuel tank, fuel pickup, the rubber lines connecting the tank pickup to the fuel lines (cracked air-sucking lines drove me crazy on a vehicle long ago), tank venting, and the actual front to back fuel lines.
The convertible fuel lines were rusty and in three parts connected by rubber line. Car ran for a short drive then wouldn't idle. Opened the carb and it was full of rust flakes from the old fuel system.
Because of the altitude here in Denver, and the newer gasoline formulations vapor lock can be an issue. I like to have an electric fuel pump mounted in the fuel tank, or very near the tank to minimize the length of the suction side of the fuel line (low pressure lowers the fuels boiling point temperature.)

 

[khryslerkid]

Get the damper replaced before something bad happens. I'm guessing you went to a big block? 440 Source has good prices on new dampers.

 

[RemCharger]

Are you thinking that the power valve kicks in at idle?

 

[Gunner1]

Hi guys.
68-500
That’s the plan now. I’m thinking 20 at idle,36 by 3000
BSB67
Cam is Isky 292 mega. 242@050 108 Lsa 104 Icl.500 lift. Speed pro 2355 .017 down .039 gasket CNC stealth heads. Compression should be about 10.5. Its pretty mild
Remcharger
I do believe the valve may be opening it’s a 4.5 and idle is 3. Plus it use to run great. After it popped back a few times I reset the timing which was off. Missed that clue Late Holley 750 dp with PV protection. I’ll mark the dist and block this time. I also think it might be opening at 3000 rpm.
CKessel 451 Mopar
Every thing in the fuel system is new. That said it’s all suspect till checked. The funny thing is it all worked great a month ago.
Khryslerkid
That’s exactly where I’m going. Hp street 7.5 pound with external weight. $149.00
It was a tire fryer two months ago.
Bob