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Old 10-18-2020, 10:24 AM   #711
HO455
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Join Date: Feb 2016
Location: Portland Oregon
Posts: 10,757
Re: Working Man's Burbon

Once I had the new distributor in the block, with the rotor aligned with #1 cylinder, it was time to preset the timing. This is where the 8* BTDC mentioned previously comes into play. It is my initial starting point.
With the crankshaft at 8* BTDC I turn the distributor so that8 #1 plug wire is clockwise from where the rotor is. About one plug wire works well (Yellow arrow in picture) I hook up my timing light and while aiming at the timing marks I slowly turn the distributor counterclockwise (blue arrow) until the timing light flashes. I stop turning the distributor and that is my preset timing. This allows me to hit the starter and have the engine start immediately so I can then set the timing properly. This works well when starting an engine for the first time.
Once started and idling I set the timing at 12 BTDC. Next step was to shut the engine off and restart it to check how it cranks over (looking for any possible kickback or slow turning of the starter indicating the timing being way off or plug wires out of order).
With nothing of concern noticed, I revved the engine a couple of times and watched to see if it came back to the same idle speed every time, which it did. It was at this point I noticed that my A/F guage was reading about 1 point higher than before. The reading had always been around 12.2 to 12.4 with the old distributor. Now it was reading 13.1 to 13.3 (Disregard the .8 in the photo as the numbers jump around and I just happened to take the photo as it flashed a high reading.) The new ignition system is obviously giving better spark than the HEI was. Time for a test drive.
The test drive revealed that I had some pinging at part throttle acceleration. I have suspected that my timing light isn't giving me accurate readings since the last time I used it. The 12* on the timing tab and where my light was indicating 12 degrees didn't agree . Whether it was the cheap aftermarket timing tab or the light I didn't know. We had set the tab to TDC by measuring piston travel. (We didn't use a degree wheel to check the accuracy of the tab or the cam timing.)
It is an adjustable light with a knob on the back and over the years I think the sticker with the degree indications has moved. So I drove over and borrowed a friend's light and sure enough it showed that I was at 17 degrees not the 12 degrees my timing light indicated. Problem detected, but how to repair the light has yet to be figured out.
Anyway with that figured out the truck was no longer pinging. With some fiddling with the idle screws the A/F ratio came up to around 13.8 to 14.2 better, but I couldn't get it to 14.9.
The idle was a bit too high and the idle adjustment screw is not holding the throttle plates open. It is as far as it can go.
So now it's back to the idle bleed adjustments that we did when the Qjet was installed. The idle bleeds in the carburetor are still too large and need to be smaller. This will will reduce the amount of emulsified fuel drawn into the idle circuit for a given amount of air flow past the throttle blades. Thus the engine will idle slower. Ideally I want to reduce that amount of fuel so I have to turn the idle set screw in about 1 turn to get the idle speed I want. Once I get to that point I should able to get the idle A/F ratio to 14.9.
With this gain in idle fuel usage and the Gearvendor overdrive I'm sure to be getting 13 MPG in town.
Time to fill up and drive.
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Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help.
RIP Bob Parks.
1967 Burban the WMB,1991 S(stink)-10 Blazer,1969 GTO, 1970 Javelin, 1952 F2 Ford 4X4, 29 Model A, 72 Firebird. 85 Alfa Romeo
If it breaks I didn't want it in the first place
The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377
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