Fuel Pressure With 0.130 Steel Needles

T

Thunderbolt

Well-Known Member
I installed new steel 0.130 needles in my QF 650 E85 carburetor since the old ones were bad.
Is it normal that only 4.5 psi is max pressure with these needle and seat assemblies before it floods?
My old needles could take 9 psi without problem. i dont know the size and type they old ones were.
I have the black plastic floats, cant go bad like brass type?
 
Thunderbolt said:
Its a Quick Fuel, QF, Holley 4150 style.
https://www.summitracing.com/int/parts/qft-ss-650-e85
Click to expand...
Holley used to make A Titanium Needle and Seat for 4150-4160- 4500 Series Carbs.
Bought one and used it when we were dirt Track Racing for the local class 2 bbl carb. Worked Responsive.
Would load up idling for a long time after an accident.
No one wanted to shut thier engines off.
Just luck of the draw most Mini Racing starters failed when Racing red hot other than Tilton Super Mini starter.

If it's not Viton tipped the carburator needle it's going to leak a small amount of gasoline closed against the fuel inlet seat.
 
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I like plastic Risoline Floats.
Have used Brass, Ok.

I would call Quick Fuel Carburator.
They Built the E85 Carb.
My advice may be wrong for You.
 
Its a street car, our Impala with 350 and 177 mini-blower, needs to be reliable. Maybe i can use viton tip needles after all with E85?
Cant find information what needles Quick Fuel equipped the carb with.
 
Quick search on google looks like viton can handle E85 after all. Cant find the original needles, would have been interesting to see if they were viton.
 
Thunderbolt said:
Its a street car, our Impala with 350 and 177 mini-blower, needs to be reliable. Maybe i can use viton tip needles after all with E85?
Cant find information what needles Quick Fuel equipped the carb with.
Click to expand...
I don't want to give wrong advice.
When you buy a High end Racing Carburator it's preset 80% out of the box for your Racing application.

The 63 Pontiac Gp with its Street Avenger carb 4150 I have dumped 100% E85 in the carb to try it out..just cruised part throttle to 100 mph to try it.
3 gallons E85.
Did Ok . Viton needle and seats.

Run E10 gasoline in it most of the time.
It's a street performance carb.
Not a drag race model.
 
Found the original needles, they are steel and marked 130. How could they hold upp to 8-9 psi for several years, and the new holley 130 needles cant handle more than 4.5 psi??? Quality issues? Using the Same fuel pump Carter M6900 run without regulator, now i must run a regulator to make it work, strange.
 
anytime old existing components are replaced with new components or gaskets are changed or replaced,
theres a potential for fit & function issues to result, gaskets, o-rings, springs all vary and over time wear.
micro trash/debris that was disturbed in and parts replacement can easily cause issues,
partially plugged fuel return lines, leaking vacuum lines,
defective sensors, defective pressure regulators ,
ethanol laced fuel, micro rust particles,
suspended in fuel leaking fuel filters,
and a myriad of other issues can be problem sources

http://garage.grumpysperformance.com/index.php?threads/fuel-pressure-regulators.635/

http://garage.grumpysperformance.com/index.php?threads/setting-up-your-fuel-system.211/

http://garage.grumpysperformance.com/index.php?threads/carb-tuning-info-and-links.109/

http://garage.grumpysperformance.co...u-need-to-know-setting-float-levels-etc.1115/

http://garage.grumpysperformance.co...n-jumping-in-with-both-feet.14918/#post-84132

http://garage.grumpysperformance.co...le-shooting-flow-chart-info.11536/#post-71845
 
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Thunderbolt said:
Found the original needles, they are steel and marked 130. How could they hold upp to 8-9 psi for several years, and the new holley 130 needles cant handle more than 4.5 psi??? Quality issues? Using the Same fuel pump Carter M6900 run without regulator, now i must run a regulator to make it work, strange.
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Viton seals superior conforms to any machining imperfections on a Micron microscopic level.
Street engines are meant to idle clean for at least 15-30 minutes without loading up.

Everyone has thier own defination of street.
 
I took a picture of the old needles that stopped sealing, they have been laying in the toolbox about one year (its a long story...).
I have seen much more worn needles in SU carburetors that worked ok, but thats almost like comparing apples to oranges....
Do they look worn? Im not sure, lack of experience.
I have some other small issues with the mini-blower install, i will post that in my "blower install thread".
index.php
 

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Thunderbolt said:
I took a picture of the old needles that stopped sealing, they have been laying in the toolbox about one year (its a long story...).
I have seen much more worn needles in SU carburetors that worked ok, but thats almost like comparing apples to oranges....
Do they look worn? Im not sure, lack of experience.
I have some other small issues with the mini-blower install, i will post that in my "blower install thread".
Click to expand...
It is what it is.

Engineers provide us with parts.
Hotrodders and mechanics try and improve.
Some items are difficult or impossible to improve without a factory machine shop and more testing.

The Rochestor Quadrajet is the most exotic elaborate carburator ever made.
Matches EFI Performance driveabilty when OEM spec cams are used.
Reached its pinnacle performance with the 1970 RAIV 400 Pontiac and 1973-74 SD455 Pontiac engine.

Holley 4bbl 4150 and 4500 Dominators most flexible for us here before EFI.
Get it done for 1/10 th of EFI Cost.
Street calibration emulsion circuits 20 mpg no Overdrive trans is possible. 14-15 mpg no sweat with no race camshaft used.
 
The originals do not look worn, a little corroded yes, but whether they sealed (or not) is the most important question.
Were they spring-loaded by any chance? Did you switch from brass to plastic floats at the same time? I'm thinking the different buoyancy would exert a different force on the needle - one type allowing for the higher fuel pressure.
 
I also think they not look worn, but they are the first used steel needles i have looked att so my lack of experience makes me unsure.

I did not change anything, it first started to flood at around 4000+ rpms and got worse (lower rpm) gradually, and after a couple of weeks of driving, finally it flooded at idle. If i adjusted one bowl so it almost sealed, the other could not seal at all, and i had to adjust the float crazy low. all the way down and that was not enough...

Could not find any debris at the needle or in the bowl that time, tried cleaning them before a changed them.

It just struck me, could it be the bowls have corroded and it leaks beside the needle assembly o-rings? I think i need to take the bowls of and inspect them close. i run 4 psi now and the fuel level is steady.


I have also thought about the fuel pump gone bad and have excessive pressure at high rpms but no sign of that when reving in neutral.
 
The E85 might have been boiling in the Fuel Bowls with the engine Hot.

Electric fans are nice but One problem with them all they do not move enough air all of them to keep the carburator float bowls cool and exhaust headers or exhaust manifolds like factory Mechanical flex fans or Mechanical Clutch fans.
None of us know exact how much air those OEM Mechanical fans move air but I think it's 10,000- 20,000 cfm with a 19 inch diameter fan...yes they use Crank Hp to turn.

Been fighting E10 gasoline boiling in hot weather in the Holley 770 cfm Carb on my 1963 Pontiac Gp.
Fine driving.
Electric Flexlite 398 Cyclone fan.
5 minutes idle time not moving the Float bowls get hot from engine heat soak.
E10 gas boils inside the Float bowls.
Dump 110 race gas in straight it runs perfect unaffected by engine heat soak.
 
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