Running out of fuel at 40-45 mph.

[geezer#99]

Originally Posted by 1970pelle

Fuel pump is in stock location, lower right front corner of the block. Has 3 lines, 3/8 line is fuel supply, 5/16 line is return to fuel tank, 1/4 line is a vent line.

I do not have a blocked vent line. I do have a vent line run and its mounted to the side of the core support and runs to the top of the support. There is a space in the support near the radiator that you can hide a hose in. I have the open end of the vent higher than the fuel tanks.

I don't have a air filter blockage, I'm using a 14X4 K&N air filter with a K&N filter top. So there is no lack of air supply.

No I'm not running a spacer between the carb and intake. I thought about it, but with the air gap intake manifold didn't feel I needed one. But willing to give one a try, I have the clearance for one.

I have breather's in both valve covers

I'm using a HEI distributor, with a adjustable vacuum advance. I have to go check my notes on how I set the timing.

Engine vacuum at idle setting still 15. Running down the road at 40-45 with my foot out of it almost 20. Now remember I'm at sea level in some places below. So I usually have more vacuum than needed.

I keep my stuff clean & neat. I have done everything asked, but it doesn't hurt to check again.

Air gap keeps the fuel vapor cooler. Heat still transfers thru the intake into the carb. Spacer will help.
And a regulator will help.

When it craps out, do you look and listen inside the carb to see what's happening?
Any flooding, leaking, boiling noises?

[1970pelle]

Originally Posted by cadillac_al

I am under the impression that you are running an electric fuel pump. I don't remember and don't see it mentioned except for the 40 gph. If it is electric and in the stock location, that is a long way to pull fuel.

40gph(Gallons Per Hour) is the stock spec for a GM mechanical fuel pump, which is what came stock on our trucks.

[1970pelle]

Originally Posted by geezer#99

Air gap keeps the fuel vapor cooler. Heat still transfers thru the intake into the carb. Spacer will help.
And a regulator will help.

When it craps out, do you look and listen inside the carb to see what's happening?
Any flooding, leaking, boiling noises?

No flooding, I would have mentioned it. No leaking, no boiling noises. I'm not having a heat issue.

[geezer#99]

Is your crate 290hp stock as delivered or where there any mods done?

[geezer#99]

Originally Posted by 1970pelle

I do not have a blocked vent line. I do have a vent line run and its mounted to the side of the core support and runs to the top of the support. There is a space in the support near the radiator that you can hide a hose in. I have the open end of the vent higher than the fuel tanks.



.

Reading back on your thread!
Why do you have this vent line like this?
Did you eliminate the charcoal canister?

[akart]

Standard mechanical fuel pumps have too much pressure for an Edelbrock carb. You may be getting too much fuel at speed. Edl fuel pump puts out about 6 lb. Stock about 15 lb. You may want to try an Edl fuel pump to match that carb.

[cadillac_al]

If he had too much fuel it would be blubbering and puffing black smoke before it died. I suspect the vent even more now that I think how mine is vented right at the tank. Routing it to the front of the vehicle is just more chance for a problem. In hindsight If 1970pelle was going to remove the charcoal canister he could have used 76 style tank vents that never fail.

[1970pelle]

I have posted or said much about my driveability issue, the truck act like its running out of fuel when at operating temp and at speeds of 35-45 mph. The issue continued to grow worse as the Florida temps continued to climb. The truck was barely driveable.Very thank full for Harley Davidson, my Black 1973 Shovelhead never missed a beat and gets 46 mpg's. It was my main mode of transport during this down time.

So the repairs on my truck, or search for the cause. I reviewed all the responses given here, Thank you all very much. And also contacted GM and Edelbrock, each since it involved there produces. GM was somewhat helpful, but wanted the truck taken to a Chevy Dealership Service Department for Diagnosis. I wasn't to keen on that Idea because of the diagnostic fee, and there lack of having anyone there who could even check the truck out.
So I dealt with it myself. I tried a different fuel tank with new fuel lines to the pump. Added a electric fuel pump in line with the mechanical pump, and could run it when condition occurs. None of these repair attempts changed anything.
I added a one inch thick Plastic Moroso spacer plate. Which made the first change in the way the engine runs. The engine idle settled down and was finally easy to get adjusted. And I was able to adjust the air/fuel mixture screws. The truck was running half way decent, I was able to drive it about 30 miles before it would start acting up. But this was happening in the morning when the ambient temps where the coolest of the day. So I was on to the problem. So I started trying different carbs, which is very hard to do. Not many have good carbs laying around for you to throw on your vehicle to test with.
I ended up buying a new carb a Quick Fuel 4 bbl 650 cfm, dual feed, electric choke. I'm sure this will be the final piece of the puzzle.
One component that surprise me that had a issue was the new HEI distributor, I had replace it when I first bought the truck. We found the gear on the distributor shaft was loose from when its was made, cause the fluctuation in timing while driving.
Will know tomorrow after the first test drive. Ken

[demian5]

Originally Posted by 1970pelle

Will know tomorrow after the first test drive. Ken

Dude what was the cause?

[1970pelle]

Looking back on this and all that was done and checked and rechecked. I never actually put my finger on the root cause.
Here is what I did that finally fixed it. I replaced a few new parts with different new parts.

1 Replaced the Edelbrock 1406 4bbl 600 cfm carb, after installing the edelbrock calibration kit and swapping around everything internal. With no change in my complaint, I did manage to have a highly tuned carb.

The replacement was a Quick Fuel Brawler 650 cfm carb. I'm telling you very impressed with the out of the box performance this carb gave me. Very easy to get it set up. Choke engine speed screw easy to get to and adjust. Idle speed settings easy to adjust, but needed to add lock tight to this screw it kept backing off loosing base idle. I will buy this brand carb again for sure.

https://www.summitracing.com/parts/q...7255/overview/

2 I also change out the intake manifold at the same time. Going with a Edelbrock Preformer Air Gap intake. This intake made a noticeable improvement in highway speed roll on performance.

3 Carter Mech. fuel pump that pumps 120 gph, #180-M4891 (Jegs)

4 engine timing I finally was happy with 30 degrees before TDC at 2000 rpm. I think I had 2 turns out on the vacuum advance. It was making 16 inches of vacuum at idle. And recovered quickly.

But that's what I did and my fuel starving issue went away. I thought I was chasing fuel that was being boiled and evaporating. But spark plugs where telling me not enough fuel. And all this was happening at high ambient temps. It was really hot that summer and early also.

Ken