Tuning your stock carb for some more power

From RPRWiki

1. Always Open Secondaries - When full throttling the stock carb from around 2500rpm, it always goes until the secondaries open and then it starts pulling a bit more. The stock vacuum source (on the passenger side) for the secondary actuator has no vacuum until it reaches around 5000rpm. So I plugged off the stock vacuum source and routed a longer hose (one from the disconnected vacuum box) to the one on the rear of the carb base (closest to the firewall)

This vacuum source has full vacuum by 2000 rpm so by 1600 rpm, it wants to pull on the linkage to open the secondaries. This is the neat part, on the passenger side of the carb, there is a linkage from the primary throttle shaft that stops the secondaries from opening until the primaries themselves are open past half throttle, and it's all progressive.

What this all means is that the secondaries will always open sooner and will react like mechanical secondaries. And yes, originally there was a slight stumble, but opening the fuel level by adjusting the screw 1/2 turn out and the idle-mixture-screw 1 turn out fixed that (I originally thought about drilling the jets but i hate messing with things that are finely designed to begin with ). Raising the fuel level has actually got the plugs to show a tan color, it was always white before (MSD 6al and coil). Comparing A to B, running with the stock setup, I felt it pull more after the secondaries open. While the modified setup felt stronger up to 5000 rpm and was more linear in power. A few runs with the G-Tech showed exactly that. So use this to tailor your power band .

2. Accellerator Pump - You can get a longer shot by bending the stop bracket (a little metal strip on the back of the carb that stops the accellerater pump arm from over travelling). I actually unscrewed the philips head screw that holds the bracket on and turned the bracket upwards so it does not even contact the arm anymore (The arm will still travel a bit more even with the throttle fully open so at least it won't damage the diaphram). I did this mod first and i think this is the main reason it did not bog as much with the secondaries opening quicker.

3. Lock Distributor Timing - To me this mod made the most difference with the other two mods complementing it. With such low compression in these EW's (Even more with a cam), adding more fuel doesn't seem to do very much without getting the timing in sooner to start burning it earlier (With a Stage 2 cam i have timing locked at 47 degrees advance and run 87 octane for the street).

 1.  Take the distributor out, remove the cap, rotor, carefully pry up the stator off the shaft.
 2.  Unscrew the ignitor, unscrew 2 philips to remove the thing that has 4 wires going to it, 
 3.  Unscrew the 2 philips head screws to remove the stationary pickup,  remove the c-clip and 2 screws that     hold the vacuum advance po.
 4.  Unscrew the 2 screws and remove the baseplate. 
 5.  Under the baseplate ,you will find the advance weights.  
 6.  Remove the 2 springs that hold the weights and with the weights held open (spin the distributor shaft in the right direction and you will see the weights fly outwards-open). 
 7.  Spot weld the weights in that position and put distributor back together. 

With all this done, even with the vacuum advance still operational, timing at idle will show it to be approximately at 32 degrees(plus or minus with the distributor still able to rotate on the heads).

There is more adjustment in the vacuum advance shaft (it will now be able to advance or retard timing a further 10 degrees). By removing the c-clip, pulling the shaft off the pin and rotating it: inwards will advance the timing or outwards will retard it.

In the picture, I removed the vacuum advance outer pot section and put 2 nuts on the shaft to not have even the vacuum advance. Strictly because I did not want any timing variables at all for my nitrous and boost setup. Removing the vacuum advance does not need to be done for street driving and will give you better mileage and will not hinder performance in any way.

Sorry I don't have pics of the distributor internals but private message me if you need better details. I pulled the distributor apart with a Haynes manual.

So with these mods, G-Tech (For what it's worth) says: Keihin with carb mods (except stock secondaries) and locked timing: 60 ft-2.472s; 330ft-6.699s; 1/8th mile- 10.253s@68.96mph; 1000ft-13.384s; 60mph-7.951s; 1/4-16.046s@81.12mph

Keihin with carb mods and locked timing: 60 ft-2.473s 330ft-6.679s 1/8th mile-10.220s@69.98mph; 1000ft-13.296s ; 60mph-7.828s; 1/4mile-16.014s@72.36mph

These numbers seem a bit off (my first time with a G-Tech Pro and I was running out of pavement! ), but for what it's worth, it definitely is a lot more fun to drive. I remember having to wring it up the rpm to get anything but at least now it has a lot more poop from idle and up.

Extensive formatting/edits by fjr0122.