Quick Fuel SS830 & fuel pressure

[gsniegow]

Hoping you can help educate me.  Last July I had some work done to the top end of my 383.  One of the changes was replacing the carb.  That shop suggested that I use a Quick Fuel carb and I approved.  Well, long story short this shop has really done a crappy job with my car.  Spent some time with my brother last night tunning things some and I am considerably happier with the assometer performance improvements.  I noticed something though which is leaving me puzzled.

Instructions read...     (http://www.quickfueltechnology.com/Instruction_Sheets/HR_Slayer_SS_Series_Instructions_Rev._1.pdf  Step 4)

"Before starting the engine make an initial check of the float level. If fuel is not visible in the sight glass. This
carburetor was pre-set at the factory to be in the middle of the sight glass at 6.5 P.S.I. Fuel pressure greater than 6.5
P.S.I. will cause the float level to be too high. Conversely, if the fuel pressure is significantly below 6.5 P.S.I. the float
level will be too low. For the carburetor to operate correctly the float levels must be in the middle of the sight glass."

My fuel pressure gauge is reading only 5psi.  After checking the manual I can confirm that the stock fuel pump on the 383 produces between 3.5 - 5 psi.  So my dumb question to you all is this...  WHAT am I losing by only supplying 5psi versus the 6.5 that the instructions say I need to have?   My float bowls showing fuel in the middle.  Things seem much better at this point, but I haven't taken it on an extended road test or anything like that.

Thank you!

~Gene

[gsniegow]

Admins:  Can you delete this tread?  I can't figure out if I have the rights to do that or not.

In talking with a friend I was able to understand the answer to my question.  My sincerest apologies for asking! 

Thank you!

[firefighter3931]

Why delete the thread....it's better to share what you learned as it may help others who have similar questions/concerns 

As for fuel pressure : The manufacturer recommends a specific value because they want the fuel bowls full at all times and especially at wide open throttle. That being said i've seen where fuel system limitations have created less than ideal wide open throttle fuel pressure....and the car still ran fine. 

I'd say that if you can maintain a solid 5psi at wide open throttle and the float level is properly set you shouldn't be experiencing any fuel starvation issues. A 383 shouldn't be going through that much fuel....even with the pedal matted to the floor 


Ron

[gsniegow]

Ron,

Thank you for the response.  Not being anywhere near as mechanical as most others on this board I didn't want to bother people if my question was stupid or common knowledge.  That being said, below is how my  friend described it in simple terms that I could understand.

He explained that the float bowls can be viewed like a household toilet.  He explained that the fuel is taken from the bottom of the bowl as needed.  Like a toilet, once the float in the tank realizes the water is decreasing it fills the tank back up.  Well the carb behaves the same way, filling the float bowls back up when the fuel is consumed.  So it was explained to me that where the psi comes into play is in keeping the float bowls leveled.  As you mentioned, in my little 383 application the current 5psi seems sufficient in keeping those bowls leveled.  I was told that if/when the next stage of my cars life comes into play that I may at that time need to replace the fuel pump, depending on the new engines needs.  But for now I should be just fine.  Further it was explained to me that if my psi was not sufficient, while driving the car at WOT it would be obvious and I would know when the float bowls were not receiving enough fuel.  It would appear that the car would be starved for fuel.  Likely would sputter as at one moment the car would not have enough gas and seem like it was dying.  Back to the toilet explanation it would be the case that the toilet handle was held down constantly allowing the water to drain from the tank and into the bowl.  That the water line feeding the toilet would not be able to provide enough water to send down to the bowl AND fill the tank as well.  I know, it's hard to explain what he told me but it certainly helped me understand what was taking place.

OK - I know that it's a odd and funny way of describing the process to me and it's certainly not a exact explanation of how the carb works in this regard.  But it certainly helped me to follow the process and clarify to me what was happening. 

Thanks again!