Fuel Pressure

[Jerry Wyss]

Was Just Wonderin how many out there use a Check Valve on They're Pipe/Tank fuel line?

 

[Ron Olson]

Probably most don't as I use that line as a vent when filling the tank. One more line to unhook then remember to reconnect. One-way valves have a tendency to have problems.

 

[Jerry Wyss]

I guess I should explain a little rather than ask a "blanket" question. While modifying an old 36" Bandit tunnel that I had

put aside 4 yrs ago, i got the boat to turn well,,very well,,I focused on the Old K&B 7.5 engine, mildly modified, AeroTec

Tunned pipe, slightly "Turboed" crank, Geraghty carb and "Sleeved" Stinger on the pipe. It ran Perdy Good; about 55 Plus,

But that eve I Got "Struck" by a notion to change back to the original stock carb,(the one with the Disc on the side), and

added a OneWay Check valve in the Pipe Pressure line. Next day,,Wow!, Where it was 55,, Now its 65!! It's approching

"Nelson" Power Head Speed. It's the Single Greatest improvement I've seen on any of my models in the 10 yrs I've been

doin this Hobby. I was just wonderin if any body else had this kind of improvement?

 

[TimD]

I've never seen a check valve used on the pressure line. Did you have to alter your needle by much to get it to run properly?

 

[Jerry Wyss]

No, I Just Used The Same K&B Remote Needle Valve I Used The Day Before With The Other Carb.It Seems to do well with

the "Spraybar" Type carb,,,Go Figure!

 

[rippinwater]

So, having made 2 changes at the same time, which do you think made the most difference, the carb or the check valve. You might want to put the Geraghty carb back on with the check valve and see if you are still up in the 60's or try the K&B carb without the check valve. Its my understanding that the check valve is more for reliability rather than performance gain. The way I had it explained to me was, that the check valve helps maintain a constant fuel cell pressure even when you chop the throttle and get into it again. So I think its more of a heat racing advantage. I could be wrong though... It wouldn't be the first time. I guess, maybe it could be maintaining fuel cell pressure between the strokes of the engine, but thats kinda hard to fathom at 20,000+ rpm. There is a guy up here in the PNW that uses them for the reason that I stated earlier. Are you out ther Gene? Correct me if I'm wrong....Please .

Craig

 

[Propjockey]

I learned about the benefits of check valves in the pressure feed years ago flying planes. If you have an engine that just doesn't want keep a good needle, try it. You may be pleasantly surprized.

 

[Jerry Wyss]

I Did Change Carbs, But Did Not Remove Check Valve. The Set Up Favored The "Spraybar" and it was obvious,,That engine

has Never Made That "Howl" Before,,,Sounds Like Someone Strong Grabbed a "Coyote" By His "Round Ones. I Remember

Usin A Check Valve on a friends Sport 40 and A Geraghty carb, It ran like "Bat Outa Hell" for a couple laps, but as I remember

the Carb adapter kept loosing up and The boat was set aside for three years until this last week. I'll try the swap around on the tunnel

first to see what accually did what. Don't Get Me Wrong I do like Geraghty Carbs,, still use the in some of my other boats,,But for

some engines a certain combo can push them over that "Edge", if you know what I mean.

 

[Jerry Wyss]

One thing I failed to mention in the last reply is that the Bandit "Killer" has a "Funny" shaped cowl back where

the tank would go,,theres not enough room for anything larger than an 8oz tank and keep high enough,,and

8oz is not enough for a 6 lap race, or even 5; so I had to put a 8oz up in the middle of the hull and a 4oz

back on a platform that I built and I'm still an inch and a 3/4 below the carb center to center. Thats what

prompted this Mod in the first place.