<div dir="ltr"><div>I recently installed an Edelbrock Performer RPM manifold and Performer 1406 carburetor on #2761, and asked Dave Londry for some tuning advice. With his permission, I am posting his advice as many can benefit from it. Thanks for the wealth of information Dave!<br>
</div><div>Peter<br>#2761<br></div><div><br></div>Here is Dave's reply:<br><div><div id=":3dk">------------------------------------------------------<br>
Beg, borrow or steal an A/F meter such as Innovate. You don't have to be very far off to feel A/F error.<br>
<a href="http://www.ebay.com/itm/Innovate-MTX-L-Digital-Wideband-Air-Fuel-Gauge-Kit-Wide-Band-WideBand-o2-Sensor-/191051619330?pt=Motors_Automotive_Tools&hash=item2c7b905c02&vxp=mtr" target="_blank">http://www.ebay.com/itm/Innovate-MTX-L-Digital-Wideband-Air-Fuel-Gauge-Kit-Wide-Band-WideBand-o2-Sensor-/191051619330?pt=Motors_Automotive_Tools&hash=item2c7b905c02&vxp=mtr</a><br>
If you do get a meter, don't run the engine without power to the O2 sensor.<br>
I wrecked one that way to learn.<br>
<br>
Having 2 is even better, and having bungs is way better than the clamp on the tailpipe.<br>
We can't all have 2 meters, but I'd stop and put a bung below the collector.<br>
I can scarcely get a reading below 2000 rpm on my car with the clamp.<br>
The exhaust reversions are pretty fierce.<br>
<br>
All the carb tuning you'll do will be about A/F.<br>
Work up from idle, because the idle setting affects operation well into primary opening.<br>
<br>
I'm assuming you have zero-ethanol gasoline,<br>
if not the A/F ratios need adjusting but I can give you the adjusted numbers<br>
<br>
1. Make sure you're happy with your timing.<br>
2. Get the idle A/F set (maybe 14.5).<br>
The edelbrock max rpm method is OK, if you can't read the A/F at idle.<br>
3. Then I'd do the ease-into-WOT runs from low (maybe 2500 to 3500) RPM<br>
and keep at it across 3500 to 4500 and 4500 to 5500 until I had it close to 12.5:1 for power.<br>
3rd gear is nice for visibility, but 2nd works if you don't have the space. (1st just goes by waay too fast)<br>
4. Next I'd do the "boot-it" checks to set the accelerator-pump stroke (nozzle also if you have to, but I doubt it)<br>
Don't worry about the meter until you get rid of any detonation.<br>
Then you can see if the meter response if fast enough to show you if you're getting too much<br>
(down toward 10:1) or too little (over 13:1) fuel during throttle opening.<br>
** Now you're power tuned. **<br>
5. You can go back and check the A/F at constant speed.<br>
(15.5:1 is nice, but unless you really care about fuel economy, anything down to 14 is OK)<br>
The higher the gear you use, the more meaningful the throttle opening is for a given rpm.<br>
(I don't look at anything under 2500 rpm - the idle screws are still dominant there anyway.)<br>
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The Edelbrock manual is pretty good about showing you how to track the metering rod/jet/spring<br>
combinations to change the A/F. Just remember that the difference between the jet and the<br>
skinny part of the metering rod is what gives you the A/F at high throttle openings.<br>
So when you get the WOT runs done, then you can adjust the constant-speed A/F by<br>
changing the fat part of the rod. Of course you won't have the rod you want.<br>
unless you bought a kit with a bunch of rods; but you can go to another rod/jet<br>
combination. Just keep the annular area of the little-end opening the same when going to the next pair.<br>
The spring just controls the the transition from big end to little end (higher/lower vacuum).<br>
It's way quick to change rods and springs, but changing jets requires taking the linkage down and the top off the body.<br>
<br>
The float levels on that carb were fine, so I'd leave them unless you see something suspicious.<br>
<br>
I've attached a chart I made of all the jet / rod openings and relative annular areas<br>
PerformerJet_Rod_Map.pdf<br>
(HiVacArea = big end, LoVacArea = little end.)<br>
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I've also attached a chart I pieced together for all the Performer and Thunder rods and jets.<br>
Performer & Thunder Rod_Jet Chart<br>
They all fit in a Performer anyway.<br>
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And for good measure - here's an A/F chart for real gasoline<br>
AirFuel_chart.jpg<br>
and a list of all the metering rod kits that Edelbrock sells.<br>
JetRod&Spring kits.pdf</div><br></div></div>