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Running out of fuel on top

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fuel running
5K views 34 replies 21 participants last post by  Moneypit 
#1 ·
So I'm running out of fuel on top end.BBC 468 with 2-660 holleys on tunnel ram with Holley fuel pump and regulator but can't tell the size of pump. Half inch lines running to pump and regulator the separate 3/8 lines to each carb. 8lbs of pressure at idle and pulls real good but runs out on top. Auto part Fuel line Wire Engine Vehicle
 
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#2 ·
So I'm running out of fuel on top end.BBC 468 with 2-660 holleys on tunnel ram with Holley fuel pump and regulator but can't tell the size of pump. Half inch lines running to pump and regulator the separate 3/8 lines to each carb. 8lbs of pressure at idle and pulls real good but runs out on top. View attachment 754450
You pump needs to be higher than your fuel tank !!
 
#8 ·
So I'm running out of fuel on top end.BBC 468 with 2-660 holleys on tunnel ram with Holley fuel pump and regulator but can't tell the size of pump. Half inch lines running to pump and regulator the separate 3/8 lines to each carb. 8lbs of pressure at idle and pulls real good but runs out on top. View attachment 754450
Couple of possibilties that have happened to me on 468's with 660's. One was the pump was weak at high flow and the stock (inexpensive) Holley regulator with an allen or straight blade screw in the bottom would not flow enough even screwed alll the way in. The regulator issue showed up this spring on a Buddy's 700HP drag car, i hadn't seen it since it was finished and he made several passes saying it was laying down on the big end, when i saw that regulator i told him to ditch it. My boat would speed up when i backed off the throttle.

Unless you have a big Nos system 8PSI seems kind of high.

Good luck.
 
#11 ·
First.....fuel pressure is less important than a system that can flow the VOLUME of fuel the engine demands on the top end. You only need 7-7.5 psi period.
Second.....if you have the very common small Holley regulator (804 part # I think), take it apart so you can see how small the fuel passage is. It is only 7/64" in diameter! If it's necessary to run a regulator...put a big one on it. Jocko
 
#13 ·
how much hp? if alot you might need to replace the needle & seats in the carb to bigger ones. they are the gate keeper of all fuel no matter what. if u got 110's put 120's in. i did big pickup tubes. big pump .bigger reg.. alcohol referenced carb etc. it all helped but the needle & seats were the main problem. . the pump could be getting weak like someone said or the jets are plugged,had a friend tell me this recently,had happened to him.
 
#14 ·
i looked at the pic again & pretty sure its your pump,it looks like a holley ,they are crap...i bought one every year because mine didn't
sound strong in the spring time when i was getting ready for boating season.it always sounded inconsistent & weak after winter.been thru like 7 holleys or more.put one on my van & it wore out completely in one year of part time driving
 
#15 ·
As mentioned hole in holley regulator is way too small, put a good regulator on it like Mallory or Aeromotive. I'm not a holley pump fan either but if putting out fuel and working properly it should put out enough.
 
#16 ·
Return line

Ditch the regulator and use a pressure poppet controlled return line to the tank. Electric pumps do not like to pump the same fuel numerous times when the demand is low. They heat up,and eventually fail. Also, where are you reading your fuel pressure @ 8 lbs?? At the regulator?? or after the regulator?
Holley electric pumps are like anything else, they work great for their designed use which is a "pusher", not a puller. They should be, as mentioned, mounted below the normal level of fuel in the tank.
Another "also", is there any chance there is something else causing the engine to lay down up top?? AND, please describe "laying down"... How far up the RPM range does it pull well? How far are you running it WOT?
Ray
 
#19 ·
Holley needle and seat should be good for up to 10 lbs. I have set up several different regulators at 9psi, including my own turbo ski race boat, so I would not worry about 8 psi. What's really important is how far does it drop at full throttle.

Holley pumps are very easy to take apart and clean and rebuild, usually without having to buy a new kit for them. The biggest problem I saw was magnets would come loose from the case from being bounced around.

Maybe I missed it, but did you check or replace your fuel filter?
 
#31 ·
Having fun yet???



OaD, the 4500 to 6200 was just MY/an example of the type of info we need to stretch this out through the weekend. How can we have a "GN7" type discussion without ALL the "facts"?? Just saying...:wink2: (Bob would be proud of us devoting an entire holiday weekend to what will, invariably turn out to be a really simple solution....:))THumbsUp:))THumbsUp:partyguy:

I ran 660's, Holley Blue Pump for 30 plus years..replaced the pump twice, and my son is still running the same set-up today.
What we did is use 1 reg. for each carb, eliminate the transfer tube, and make dual feed's out of them...so 2 line's from the pump
and we used the small regs also....I had a vent problem on my boat, it didn't lay down, it just quit
Yep, there are many many boats/hot rods out there running the basic set up like his for years without any issues...
My Hydroflite seemed to nose over a bit up top. (AND the pressure would fall down to 2-3-4...) Like you, I used two tanks to two pumps, to two filters, to two regulators, to two f/pressure gauges, and finally, to two carbs. Problem solved.....
My issue was the two side tanks feeding,(T'd into), a single pump. For some reason it wouldn't maintain a steady flow?
Ray
 
#28 ·
660's

I ran 660's, Holley Blue Pump for 30 plus years..replaced the pump twice, and my son is still running the same set-up today.
What we did is use 1 reg. for each carb, eliminate the transfer tube, and make dual feed's out of them...so 2 line's from the pump
and we used the small regs also....I had a vent problem on my boat, it didn't lay down, it just quit
 
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