Tuning with jets, Power valves and an O2 guage

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The GV needs to be tucked up and you will want to verify your pinion angle when it's done. That should require adjustment.
I think frustration got the best of you. Hopefully you can get it worked out and vibration free. Nothing is "traditional" when you take a driveline package the factory never offered, modify it in bits and pieces, and then bolt it all together. The process requires atttention to detail and persistance from the get-go. I hope you can find your happy place because if you think timing's too much - wait until you start the driveline vibration bit...
 
After having the heads ported and going with the thicker .075 head gaskets, I'm now at 10.07 to one. All test drives have shown the car to have ZERO detoantion! Now I'm back to tuning it. I took the wife along today to record the Air Fuel readings from the guage while I drove the car.

Todays report:

* Idle in Neutral 1100-1200 rpms 13.1 to 13.5
* Idle in Gear 750-800 rpms 17.8 to 18.0 +

* Slow acceleration from 2000-3500 rpms 10,9 to 11.6
* Slow acceleration from 3000-5000 rpms 11.9 to 12.4

* Steady cruise @ 40 mph in OD 12.9 to 13.3
* Steady cruise @ 50 mph in OD 12.0 to 12.5
* Steady cruise @ 60 mph in OD 11.9 to 12.3

* Faster acceleration from 2000-3500 rpms 11.5 to 12.0
* Faster acceleration from 3000-5000 rpms 12.6 to 13.1

* WOT in 2nd gear, 2000-3500 rpms 12.9 to 13.1
* WOT in 2nd gear, 3500-6000 rpms 11.8 to 12.5
* Repeat run 11.6 to 12.1

*********************************************************************

With this info, I see that I need to richen it up a bunch at idle in gear. It stumbled and stalled twice while leaving 2 different stop signs. I suppose that since this occurs at idle and not on the primary circuit, this is a matter of tweaking the idle mixture screws?
I wouldn't think it would need more accelerator pump volume would it?

The "Slow acceleration" between 2000-3500 and 3000 to 5000 showed it to be really rich. This was done at light throttle , I assume entirely on the primary circuit? This makes me think I need to use smaller primary jets.

Steady cruise at 40, 50 and 60 were done in overdrive resulting in a final drive of 3.05 to one. The numbers there are more like what I'm supposed to have at WOT.

The faster acceleration testing showed leaner numbers than the slow acceleration. This was still done without hearing the secondaries open. I'm not sure what to make of that. Maybe I need a power valve that opens sooner there? I have a 3.5 in the carb now.

At WOT it shows that the higher RPMs it goes fatter. I guess that is safer than leaning out.

I welcome any suggestions or comments on my findings.
My gut tells me to adjust the idle mixture screws to obtain a richer in gear reading. It tells me to lean out the jetting front and rear. I'm not sure what to do regarding the Power valve. I'm not sure if I should use a lower rated one than the 3.5 I have.
Please tell me what you think!
 
srixon4406 said:
Get a assortment of pump cams for off idle issues. Also make sure your rear throttle blades are adjusted properly. Any time you make a timing change the carb is going to need to be retuned. Power valve and jets don't come into play till after the transition period.
Aaron
Click to expand...


THIS...........Lots of people buy into the 1/2 pv of idle vac bs and it means nothing if the carb`s set up correctly on the idle circuit. Even if it`s open which a low pv would be it`s not coming into play until you`re in the cruse/power circuit and into the boosters. The proper way to tune pv`s is to hook up a vac gauge and check your cruise vac and in my case 9-10'`s and get the pv to be under that amount according to how fast you want/need the enrichment.................that`s the short version. Peace!
 
Last weekend I drove the car on a 950 mile round trip from Northern CA to L.A. for the Spring Fling. The car ran great and had no problems. The A/F was reading between 11.9 to 13.0 at a 65-70 mph cruise. It leaned out a bit when I tipped the throttle at that speed then settled back to 13.0 at cruise.
At home i figured I'd try leaning out the primary circuit so I pulled the #83 jets and put in #81s. The car ran a bit leaner in the 12.4 to 13.8 range but power dropped off and it actually detonated a little on one hard WOT run. I put the #83s back in and readjusted the idle mixture screws again. The power came back and no knock either.
This engine must like the richer mix. I'm leaving it that way for now.
Thanks, Greg
 
I've been busy with other stuff, but I'm still curious if I can get this thing tuned right.
I have been looking at some other threads elsewhere on tuning. I read where it was suggested to run smaller jets for leaner cruise A/F numbers but then enlarging the Power Valve Channel Restriction. Sounds good to me. I haven't tried it yet but I'm tempted to buy another metering block to modify, OR....
I have several Holley metering blocks to practice with. I'd prefer to screw up with a throwaway piece.
 
Frankenduster said:
I've been busy with other stuff, but I'm still curious if I can get this thing tuned right.
I have been looking at some other threads elsewhere on tuning. I read where it was suggested to run smaller jets for leaner cruise A/F numbers but then enlarging the Power Valve Channel Restriction. Sounds good to me. I haven't tried it yet but I'm tempted to buy another metering block to modify, OR....
I have several Holley metering blocks to practice with. I'd prefer to screw up with a throwaway piece.
Click to expand...

This is the correct way to tune the carb. The main jets are for your cruise setting, not WOT as many think.. The power valve is your WOT or under load setting. The power valve orifice is the one you enlarge or reduce to get the correct values at WOT.
Just make sure that your carb is not too small as it will become a restriction at WOT , build vacuum again in the intake and close the power valve, if it is at a very low value. You will then get a leaning out situation at high RPM... not good..
 
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