here is the chart from RobbMC for their olds 550HP pump...the first chart is free flow, the 2nd chart is @ 4.5psi:

http://www.robbmcperformance.com/products/olds550.html

you can see it pumps well over 60GPH @ 4000 & 5000 RPM (4.5psi)...so this pump, my new 3/8 sending unit, pressure regulator and a new fuel filter should supply plenty of fuel for my current & future needs.

 

How is vapor lock occurring when fuel is flowing at it's max? During idle or low speed the fuel has longer to boil. Right?

You are correct that as pressure increases, flow will decrease. This is bernoulli's equation. But, my question now it, is your motor stock? If it's not heavily modified, how can you be overloading the fuel pump, unless the fuel pump is tired and not performing at it's full. Now I don't have a 320 hp motor, I think a 72 cutlass is rated for maybe 200 max. And I'm having a similar problem with my ebrock 600 carb. As far as I can tell, my fuel pump is nothing special, just a replacement like you could get from fusick or year one.

What i'm getting at is, if I'm having a similar problem with 100hp less, and a similar fuel pump, could there be another problem? Could it be a short coming in the carb?

 

Just for the halibut, change the 6-8-10 inches of rubber fuel line between the steel line and the pump.
I've heard more than 1 story of them collapsing internally or 'pinholes' that'll suck air under high flow situations.

 

I'm gonna see what this guy says about it this weekend. He's gonna time it correctly if it isn't already, fill the tank with gas, take it for a ride and put it to the floor to see what happens when it hits third. If he concludes it's fuel delivery issues, then I'll see what he suggests as a remedy. I've also been thinking, if I end up having him do the heads and cam, I'm gonna need to upgrade my fuel system anyway.

As far as the vapor lock...it was just something I thought may be the problem, not quite familiar with it honestly. In my research, it was something I came across.

I'm pretty sure I have a 3/8" hard line front to back already (I'll have to check). Also, the sending unit I'm going to install is a vapor return style unit. So if I went with the RobbMC pump (with return option) and a regulator I could incorporate a return line...then I should not have to worry about fuel supply anymore, up to 550hp anyway.

 

If it were the carb, I would think 1st & 2nd would be affected as well.

 

You are getting into the term I like to call mental ************! It's what happens when you get all wrapped up in assumptions, what if's, and technical BS. Your engine nor your powertrain is anything special. A common off the shelf fuel pump is fine your application.

Why don't you wait until your friend does a bit of trouble shooting and go from there?

 

well, i did say i was going to let him do his thing this weekend and see what he says, so yes, that is my plan.....however, he already said it sounds like a fuel supply issue. i am preparing myself to know what kind of money will need to be spent if i do have a fuel delivery problem. i have not touched my fuel tank or fuel sending unit at all in the 14 years i have owned the car, it sits all winter and doesn't move for 6 months, it's probably got the original tank which is probably full of crap. my fuel system is something that i really have not paid any attention to since i got this car, aside from an aftermarket fuel pump about 6-8 years ago and a few new fuel filters and rubber lines.

i think it ONLY MAKES SENSE that i may need a major fuel system overhaul, not only because of my engines CURRENT demand, but because of what it's FUTURE demand will be as well. are you saying it wouldn't be a good idea to put in a new clean gas tank?? fresh sending unit with clean sock??? high volume pump?? bigger lines??

last i checked, my decision to ********** involves nobody but myself, not sure why you would be bothered by it. my plans for this car is MORE POWER TO THE GROUND!!! i'm not just gonna leave the car as is and drive it for the rest of my life.....i'm constantly upgrading with the funds that are available to me. my engine and drivetrain may not be "anything special" but it's 10x better than it was when i got the car and will continue to get better. it may not be anything special to you, considering your sitting on a 468ci, but it's pretty special to me. if i want a top of the line fuel delivery system so i don't have to worry about it, then that's what i'll have. you make it seem like i shouldn't replace my sending unit, or that i shouldn't get a high volume pump...but they sure as hell won't hurt. if i had the "just leave everything as it is" mentality, then i wouldn't have the car i have today, neither would you. hell, i'd even consider upgrading the fuel system even if i didn't have a problem, LOL.

here are a few pics of my friends 69 442, 468ci...motor alone 510HP, w/ NOS 760HP:







he recently installed a ram air induction system:

 

still could be the float level, Tony got his ebrock new and his floats were messed up outta the box.


@ JPC I have a 600 ebrock on my 72 350 w no issues goes from 0 mph right to ~5k rpms in first and second and keeps going in third till I let off It. IDT its something inherently wrong w the carb...

 

so, just to be clear....if the float level is the issue, i would need to raise the float level to correct the problem, right??

 

Thats nice ride your friend has there, and yes, your car has come a long way! However, just to throw money and parts at things that won't neccessarily improve your setup is not what most of us do. Your problem may or may not be a function of your fuel system. Your fuel system is probably more than adaquate for your setup IF it's functioning properly.

I meant by the term nothing special, as in not really super high HP. Btw, my 468 runs off a stock pump, original lines except rubber parts, and original tank and internals.

I meant what I said as encouragment, not to degrade. My point in all this is I hate to speculate, I troubleshoot and repair/ or improve as required!

 

i was under the impression that a fuel pump either works or it doesn't, but apparantly they can get tired/worn and not be fully funtional. so i am thinking that it may be the case with my pump, as it is about 6-8 years old. i forgot about this, but last year i started her up one day and while it was warming up i smelled serious fuel, looked under the car and saw some fuel leaking onto the driveway. so i got down on the ground to check it out and it was leaking from the gasket on the fuel pump itself. i popped the cover off the fuel pump and replaced the gasket, as it was all dried up and cracking. i made the new gasket out of some thin rubber material i had kicking around. so now i wonder, maybe the pump doesn't have a good enough seal for high fuel demand situations.

 

and looking to get educated, ok

the Poster says his car goes to 5K rpm in first no issues, ok less load on the motor etc because of the gearing, fuel, timing etc are fine, shifts well, does the same thing goes to 5K in second no issues, I would think the motor has a little LESS load as it is moving already, ok shifts to third and then there are issues? ok so what is the difference of the motor going to 5 K, gearing , but there is more or less load on the motor? I mean there is inertia etc right? the motor is making the same horsepower, going to the same rpm range, and my understanding is how quick it does it's work is a reflection of horsepower? I am truly trying to figure this all out in my head and pardon if it is a newb question. another thought is it that the fuel is being sent to the back of the tank? and maybe there isn't enough by the pick-up? does this happen with a full tank? I know some racing tanks have little resevoirs? and lower their pick up point.

that said I will put a few chips on the timing as a major part of the problem, different vacuum advance due to load, and available vacuum.

great thread.....

 

Okay guys, my fuel volume to the carb is my problem. My timing was off a few degrees. It was at about 8 degrees idle, he brought it up to around 12 which seemed to make my motor happy. 3200 rpm put it at about 34 degrees all in. It def runs better and has a little more snap too it. But, it still bogs down on me under WOT. I ket him drive it and his first reaction was acting like it was running out of gas. Judging by the age of the fuel pump and the symptoms, he thinks a new fuel pump with a pressure regulator, along with the new sending unit should take care of the problem. He also said the carb seems to be doing it's job correctly, as it performs well when fuel is available. So I am gonna step up the fuel system so it's ready for the work about to take place this winter.

Which brings me to my next subject. I'm gonna let him rip into the top end of my motor this fall. He already has a set of roller rockers that he's putting aside for me, and he's going to do sone research for me, figure out what I'll need for parts (lifters, springs, valves, gaskets, hardware, etc) and give me a list of part numbers so I can buy all the parts first. Come fall, he's gonna rip off the heads, strip them, and send them to a machine shop he deals with to go through them. They'll get blasted, shaved down, drilled out for 3/8" rocker studs, bigger valves, & port and polish. Plus he'll get me a cam & lifters to compliment everything. After all is said and done, it'll cost me about the same as a set of Edelbrock heads, but includes the dissasembly, machine work, parts, labor & reassembly. About $1800...and he says 420hp is attainable at that cost.

 

Your HEI is only at 12 *? Is it like a mallory or aftermarket? Mine hasn't been reclocked (I think thats the right term), so mine is up around 16 or so, judging off the stock timing tab. According to many member in my local club, this is common for the HEI systems on the older motors. It's a GM HEI unit of of say a 77 rocket 350 motor.

How did he judge that the carb was okay? What did he look for that it was doing correctly when it was getting fuel? I might try to measure my fuel pressure coming out of the pump this weekend and see if mine isn't up to par.

 

I wanted to chime back in here for record purposes and for anyone else who might ever have problems. I have found the root source of the problem. A couple of years back I was at a car show and a bunch of guys were looking at my car, and how I had my fuel filter after the mechanical pump on the block. They said it was dangerous because it could catch fire if it ever leaked, so I ended up putting it before the pump after the lines come out the the frame.

Well yesterday a local guy mentioned I should try changing that. Today I bought some new lines, a new filter and put the filter on. I started the car, let it run for a few minutes and took off down the street. No carb adjustment(I had it set to from before when the filter was on before the pump) and :




(Yeah I know it's only a peg-leg, :/ It's 103' 4" without brakes, all gas.) So my question is, how does the engine starve for fuel with a Fram G2 filter before the pump, but not after? I know obviously the filter is under suction before the pump and pressure after the pump, but I don't get it.