Fuel volume drop after regulator?

[Adger Smith]

Kevin,
OK, we've seen yours, now take a look at my belly button...... :~)
Since you are talking about school, you should be familiar with math and if you studied engineering you should be familiar with fluid dynamics. It's all about math. You and I can sit at our computer and do the math on the fuel flow required to make the HP for a BB to go in the low 10's. It is a shame your shop teacher didn't take the time to study the system he was using. Check the float drop and fuel flow capacity of that Q Jet with the .149 N/S and then pull the Holley regulator apart and do the math on it. You are right about one thing. He didn't need a $1000 system, just a few upgraded components to match the fuel flow capacity of the carb he was using. If he had he might have been able to go some high 9's with that BB.

[Kevin Lang]

First of all Adger,I never said i studied engineering or fluid dynamics, it doesn't take a rocket scientist to know that more volume flows through a .250 hole in the reg. than a .149 hole in the carb. at the same pressure. Being that we drop the pressure after the reg. to 6-6.5 psi. the only way to put more volume through that hole is to UP the pressure which will force the float against the top of the carb. and flood the engine with fuel. YOU do the math!!! Good luck and God bless!

[Duane Eiskant II]

Well, I'm not a rocket scientist by any means but on my stocker with the autolite carb i use to run a black pump (Holley 150 gph) with the Mallory regulator and #8 fuel lines. I went to work for a carb shop and got a lesson in fuel systems. Put a magnafuel 300 (bypass pressure is somewhere around 40 lbs that it sends to the front), with the magnafuel regulator and #10 line from the cell right to the inlet of the carb. It was worth a solid .15 over my old system. Also i run 9 1/2 psi at the carb, i get the fuel pressure right at the needle and seat and it never changes. Made me a believer in the bigger and better pumps. On a side note, a very fast upper classed stocker (he would kill me if i let you all know just how smart he is), was having a fuel issue. He has a Mallory pump and regulator and has run his car that way since he built it. He was thinking he was running out of fuel before the finish line so i made him up a fitting and a gauge to see how much psi his pump was pushing to the regulator. His autometer fuel pressure gauge always showed he had 8 psi with his Holley carb. Well, we went to the race track, and i checked his bypass pressure it was only sending 5 psi to the front so how was his other gauge showing 8 in the car? He didn't like the way the pump "sounded" when i turned the pressure up to 25 so, we set it at 15. Still picked up about .07, but id bet theres still more et that's he is not using. You know thought, you just cant teach an old dog new tricks....Of course he's one of the types that you can't teach anything, because he knows it all...

[Adger Smith]

Kevin,
I see you have fallen victim of the old story of increasing pressure to maximize flow. It will increase flow, but not nearly as much as is generally thought. Yes, I have done the math. I have a real nice spread sheet I use at the dyno for determining the fuel flow of different size jets at various pressures. When you are dealing with NOS these pressures & flows become very critical.
There is a limit to the amount of fuel pressure that a float can see & hold the N/S closed. That pressure goes down as the seat area is increased.
There is another issue with fuel that is often overlooked. "Air in the fuel". High pressure is your enemy when putting fuel in the float bowl without being air entrained. I think everyone has put a garden hose in a bucket. What happens when you put the high pressure nozzle vs the open hose in the bucket?
If you really want a solid slug of fuel to the N/S put about a .060-.070 bypass jet in front of the regulator and about a .040 jet as close to the out side of the regulator as you can.

[Kenny Wigington]

Ok, well, with a Holley, almost any Holley, has 2 fuel bowls, generous sized, at that and 2 lines feeding them. #6 minimum ? Q Jets have less than 1/2 of one of those, total. So you "stack" the fuel in front of it. I found that same thing with oversizing line, and it showed some good solid improvement, especially in back half.

[Duane Eiskant II]

Kenny, ding, ding, ding !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[james schaechter]

Originally Posted by Kevin Lang

It escapes me how people have to put a $1,000 fuel system on a Q-jet car when they could hook a 3" hose to a tanker truck and still have a .149 needle and seat to pass it through. My auto shop teacher in high school had a 68 camaro big block 427 and Q-jet with a Holley blue pump and Holley reg. and went 10.28 but a 305 Q-jet combo needs a nitro pump on it ??? It seems more attention to mounting and plumbing is what is needed. Just my opinion. Like belly buttons ..... everybody got one!

The old holleys were it years ago. I remember having to put the big springs, big line, 2 pumps mandatory and that was with a Holley carb! It seemed like you had to take them apart and clean them thoroughly each season at a minimum. The regulators were something you cussed at and hit with a screwdriver handle more than adjusted! LOL.

I drove a SSAS in early 80s. We always did the burnout with one pump on then turned the other one on to stage. Dumb me forgot one. I made it part way through low gear before it about quit running!

There are some real good fuel systems out there that just weren't around back in the day. Mounting and all that has to be good, but the fast Q jet cars typically have well prepared systems that might look like overkill and maybe are just enough.

This doesn't mean that a car can't run with a Q jet and a Big Block with a holley blue, etc. , but when you are racing stock, the usually calculations don't always apply. You have to give the car what it wants, even if it is different than every body else's.

We run a magnafuel pump and a product engineering Qjet bypass regulator and am very happy with it. Just a 327 stocker Stickshift combo in E/Stick. I would not go smaller than what we have, even if it seems like it is too much to the casual observer. It doesn't flood, I can tune it, it doesn't flat out. The pump has proven to be very reliable too.