Carb Problem?

[Hal Copple]

I have studied my several Holley's and made any number of modifications, some not so successful, to them. Here are my opinions. On my Edlebrock RPM intake manifold, the right and left sides are separated by a plenum divider. I tried an open half inch spacer, to reduce winter gas fuel/carb percolation. It did not run quite so well, as when i kept the separation with a four hole spacer. (The four hole spacer gives a more accurate "signal" to the boosters). On my first vac sec 750, i put on a 50cc "squirter", it did nothing, good or bad. I cut off the choke horn, to make the air flow under the aircleaner top less abrupt. I noted that the "booster" venturies were straight, and not downleg, and wondered then if they metered less accurately, allowing perhaps some unmetered air to flow around and down the venturies, since i changed the air flow path by cutting off the choke tower.

But it seemed to run fine, and actually seemed to get better mpg, although my ET's in the quarter mile were a bit slower after this.

Took out the sintered bronze fuel inlet filters, and ran a large Holley canister filter, found it necessary by watching my fuel pressure on long WOT, to change it about every 10K miles, due to debris in the fuel. Even with the huge holley filtter.

Put on AN 8 lines, .10 needle and seat, plenty of gas, had enought before this. Put on all radiused hard fuel connections, no abrupt right angle fittings anywhere in my fuel system. Run the Carter mechanical pump, running always 7.4 psi.

Learned that it was necessary to have a little bit of slack in the squirter to avoid too much fuel with abrupt throttle "tip in."

Drove around with a vacuum gage hooked up, watching my vacuum under light load, to determine that a 6.5 power valve was best, and safest, and worked the best. Dilegently studied power valve theory to determine this.

Had the first carb on a chassis dyno, put in the white or lightest spring in the vacuum actuation, picked up 40 hp in the mid ranges.

Put on a 750 Pro HP, vac secondary. put in the white spring, put on a slightly smaller squirter nozzle, so i have a less abrupt but longer "squirt", this carb had down leg boosters, run 70 front and 72 rears, with brass floats which have a longer arm to ensure the fuel supply is cut off even with my higher fuel pressure, as the shorter arm on the stock Nitrophil floats may not have enough leverage to do this reliably.

In the end, using Bob Olhtoff's suggestions , my stroked windsor has a vac sec Holley 750 Pro, 30cc squirter, sitting over a half inch four hole spacer, on a divided plenum RPM intake, feeding Twisted Wedge heads. the linkage cam is the stock one, set with the standard screw setting. Three inch 14 inch round K&N air filter, chrome top, the pleated K&N top upset the air flow into the engine.

My driveability is perfect. I can run my car down to 900 rpm in fifth, and and accelerate without protest to 6000 rpm, with absolutely no hesitation or stumble anywhere, with a torque curve on the dyno that is perfectly smooth, without any jags or other indications of improper fuel delivery. I have excellent MPG, about 15-18 mpg at cruise.

assuming no fuel leaks, and proper floats and float levels, i sometimes think that when people have a problem with stumble or hesitation, they assume the engine needs more gas, while actually, in my case every time, the engine needed less gas on "tip in", to avoid momentary richness and "bog". Larger jets made for worse drivabilty, so went back to Bob's suggestions, and it ran better.

In other words, sometimes less is best.

Planning on a littel 500 mile trip to Ohio friday, back sunday, should be a fine trip.