max fuel pressure w/holley? tried 18 psi, got it to work

[Matt Gruber]

made some mods and it works w/ 18 psi. but i chickened out and went back to 5-6 psi. Anyone think 18 is safe? anyone go HIGHER? How high?

[hondo383]

why?

[Matt Gruber]

why?

why do they sell pumps over 6 psi?
.
why do many new cars w/EFI use 40-45 psi?

[F1Fever]

very odd you bring this up, we were just discussing this yesterday for a turbo app....

[Matt Gruber]

very odd you bring this up, we were just discussing this yesterday for a turbo app....

would be easy to run up to ~14 psi boost w/blow thru if the carb can take 18.

[Stan Weiss]

why?

why do they sell pumps over 6 psi?
.
why do many new cars w/EFI use 40-45 psi?

In your carb you are just filling the bowl. If 6 or 7 psi does the job why have the needle and seat work with more pressure then is needed.

The EFI is designed for a spray patter and the higher fuel pressure increases flow rating. So use as high as 3.75 - 4 bars.

Stan

[Matt Gruber]

why?

why do they sell pumps over 6 psi?

In your carb you are just filling the bowl. If 6 or 7 psi does the job why have the needle and seat work with more pressure then is needed.

Stan

Exactly! THAT is why i went back to my old fuel pump.
But, there appears to be guys that might NEED that capacity, like with a blower.

[bigjoe1]

Hulley carbs are designed for 6 psi===what are you trying to prove ??


JOE SHERMAN RACING

[Matt Gruber]

Hulley carbs are designed for 6 psi===what are you trying to prove ??


JOE SHERMAN RACING

Joe
i bought a carter fuel pump at a swap meet. it was the exact same model i was using for 10 years. it flooded and i thought it must be 1 or 2 psi higher than my old pump. so i fixed the carb so it didn't flood. then i got to thinking, "i better check the psi" so i put my gauge on and it pegs it. so i dug up a higher gauge and it was 18! so i put my 10 yr old pump back on.
So, i posted it here in case it might be an interesting topic for racers. i'm afraid to use it, but, maybe i'll learn something.
Thanks for asking! I enjoy reading your posts! You have an amazing amount of experience!

[bigjoe1]

people who think more pressure is better are wrong=== I know for a fact that some Prostock racers only run 3,5 to 4.0 pounds on a 1460 horsepower engine= If it seems like more pressure is better , there is something else VERY WRONG


JOE SHERMAN RACING

[cjperformance]

When running as blow thru you need to remember that the fuel inlet pressure may be higher than 4-6psi BUT this pressure will be relative to the boost pressure that is inside the fuel bowl. IE- if you run 10psi boost in blow thru form then to maintain a relative fuel pressure of say 6psi you need 16psi in the fuel line. In this instance the needle and seat only sees this ar 6psi ( the difference between bowl pressure(from boost) and fuel inlet pressure.)

As Joe says, too much pressure is not so good with a carb. The more pressure thru the needle and seat, the more fuel foaming/airation will occur which is BAD for maintaining an accurate feel curve. If you cant get enough fuel flow in there with 5psi in the line, then you need to rework the fuel system to flow more fuel at 5psi.

[Dodge Freak]

More PSI means easier to leak fuel Only "benefit" I can think of, lol.

[R.Olds]

Hulley carbs are designed for 6 psi===what are you trying to prove ??


JOE SHERMAN RACING

Joe
i bought a carter fuel pump at a swap meet. it was the exact same model i was using for 10 years. it flooded and i thought it must be 1 or 2 psi higher than my old pump. so i fixed the carb so it didn't flood. then i got to thinking, "i better check the psi" so i put my gauge on and it pegs it. so i dug up a higher gauge and it was 18! so i put my 10 yr old pump back on.
So, i posted it here in case it might be an interesting topic for racers. i'm afraid to use it, but, maybe i'll learn something.
Thanks for asking! I enjoy reading your posts! You have an amazing amount of experience!

The self regulated Carters are total junk, I have seen a dozen in the last year that did not work as advertised,. pressures from 2 psi to 16 psi, and never consistant. Now I use the non regulated Carters with seperate regulator.

Rick

[BrazilianZ28Camaro]

Hulley carbs are designed for 6 psi===what are you trying to prove ??


JOE SHERMAN RACING

Joe
i bought a carter fuel pump at a swap meet. it was the exact same model i was using for 10 years. it flooded and i thought it must be 1 or 2 psi higher than my old pump. so i fixed the carb so it didn't flood. then i got to thinking, "i better check the psi" so i put my gauge on and it pegs it. so i dug up a higher gauge and it was 18! so i put my 10 yr old pump back on.
So, i posted it here in case it might be an interesting topic for racers. i'm afraid to use it, but, maybe i'll learn something.
Thanks for asking! I enjoy reading your posts! You have an amazing amount of experience!

The self regulated Carters are total junk, I have seen a dozen in the last year that did not work as advertised,. pressures from 2 psi to 16 psi, and never consistant. Now I use the non regulated Carters with seperate regulator.

Rick

I've a carter mechanical hi volume pump(CRT-M6624) in my SBC and it varies the pressure all the way from 4 to 16 psi ...

With the engine hot the pressure is aways low...I thought that it had a vapor lock problem or something...

Now this tread help me put the guilt on my pump!

[Stan Weiss]

When running as blow thru you need to remember that the fuel inlet pressure may be higher than 4-6psi BUT this pressure will be relative to the boost pressure that is inside the fuel bowl. IE- if you run 10psi boost in blow thru form then to maintain a relative fuel pressure of say 6psi you need 16psi in the fuel line. In this instance the needle and seat only sees this ar 6psi ( the difference between bowl pressure(from boost) and fuel inlet pressure.)

As Joe says, too much pressure is not so good with a carb. The more pressure thru the needle and seat, the more fuel foaming/airation will occur which is BAD for maintaining an accurate feel curve. If you cant get enough fuel flow in there with 5psi in the line, then you need to rework the fuel system to flow more fuel at 5psi.

Shouldn't this be done with a boost reference regulator and not running the higher pressure all of the time?

Stan