Chapter 19

Latest Entry

11/12/01  Well, TurboStude now has a new air hat (with sieve) which works really 
well.  Finally got the A/F ratio on WOT into the >0.9 volt region using that and some really skinny needles usually reserved for the bigger CFM Edelbrocks, and the modified Holley red pump in line with the boost referenced 12-803 Holley regulator.  I have boost (2 psi over atm) from about 2000 rpm up to 5000 rpm (15 psi over atm). I developed a crack in the air hat, maybe from boost, or maybe due to the minimal clearance I had with the lip on the air-horn, but corrected this with an "air-hat corset....".  The "dead-head" Holley regulator diaphragm sprung a leak, and now I guess I'd better bite the bullet and get a return type regulator. I asked around on the Blowthru list and a response came from Oz Cheek.   He has had very good luck with his mod:  Oz Cheek regulator modification

The advantage to a return type regulator is that it doesn't build up back-pressure in the fuel supply line, but rather re-routes the fuel back to the tank.  This is easier on the pump, which in turn runs cooler and presumably will last longer.  In terms of flow, a return type regulator can provide fuel delivery unimpeded to the carb.  All that fuss we make over large line, minimal bends, and then we slam it into a little hole in a dead-head regulator.  I believe the trick with the return type is to provide a rather large bore return line.   Jon Myer's "Spooky" Stude uses a regulator, not ON the line between the pump and the carb, but off of a "Tee" in that line.  Since I'm not likely to be making 500 hp with TurboStude, I don't know how important that part is....   I'll try to reproduce Oz's regulator mods on my leaky one.  I'm also keeping my eyes open for a Mallory 4309 return style regulator, as this seems to be the one most are using, and is my fall-back if I can't come up to Oz's machining standards of excellence.  Before I sprung a leak, I did start running faster, and began to tweak the timing.  It still idles sort of fast, and this may be timing or possibly a vacuum leak still present at the intake manifold where I broke off that stud the night before Back-to the 50's.  It may be that bigger primary jets are still the answer at idle, at least for the time being. 

The hood is now back on, the original, without holes.  The car looks almost normal!  I'll fix that with a couple of TURBO name-plates I pried off of a LeBaron and carved a bit to remove the "fuel injected" logo underneath.  Tonight, I'll rebracket the heater fan to fit in the engine compartment again.  Then we'll see about windshield wipers.   In the spring, maybe I'll return to the abbreviated hood to make tuning easier and upset the purists......

11/19/01 Well, I have made the  mods  to my regulator as well as some "porting" to the inside of the regulator to allow fuel to "cross" the regulator to leave thru the 3/8 inch return line which is plumbed straight back into the tank. The only impedance in the line is a 90 degree bend where it enters the top of the tank thru the sending unit. With the adjuster screw backed almost all the way out, the fuel pressure gauge does not register, and the carb needs to fill up its bowl by prolonged cranking, then runs until it runs out of gas. All this talk about large return lines , but with "our" modification, I think there will need to be some resistance on the return line, or the pressure will not build up enough in the regulator to lift up the diaphragm. I will add a small in-line fuel tap on the return line, and play with resistance. Despite my pressure problem, which Oz didn't have, I still like the idea of hogging out the inside of the modified regulator, since the wear marks where the nipple contacted the metal part of the diaphragm in Oz's regulator are uneven. Having equal pressure on all points of the diaphragm (Pascal's law?) should, theoretically, raise it straight up, and pass more fuel. I wonder whether the weaker spring which comes with the regulator diaphragm repair kit would be better to add than more resistance in the return line?! I can also play with the height of the nipple in the regulator body, to create a pre-determined annular orifice when the regulator is at rest with whatever spring is pushing against the diaphragm.  Now to fiddle.  At least I don't have any fuel leaking anywhere with all the new fittings.....

11/20/01  Of course, when one has a pre-conceived notion of how things work, they don't follow instructions.  Though I built a great regulator, I hooked it up wrong!  The fuel should flow across the regulator body into the carb, with the return going down the stand-pipe(center connection). Oz's instructions were correct.  Now, with the change, I get a pulsating 5.5 to 6 pounds at the gauge at idle.  Spun up a nicer preload adjuster with the boost reference tube running down the center, out of a bolt.  This is sturdier than the off-center drilled piece I was using with the soldered in nipple.  It was too dark to see the gauges last night, so I didn't go very far with the car, but tonight I will see how the fuel pressure matches boost.  Theoretically, since the boost will be traveling up to 15#, the fuel pressure should be 15+5.5=20.5# at about 5000rpm....