Cliff's Quadrajet Parts and Rebuild Kits

  Just got done checking the timing on my truck and it's advancing exactly like the test did, so I've got a 21° mechanical advance, with a 10° initial, and 15°'s of vacuum advance, for a total of 46° @3500 rpm under light load.
 Still have to do a road test to see how it performs, but I'm fairly confident it's going to be fine.

 I did re-jet the carb from 74's to 73's and raised the LIAB's to  .067" from  .066".
 Trying to squeeze as much mileage as I can without doing any damage. The price of gas is killing me at 10 mpg. (Of course keeping my foot out of it might help just a tad bit, or so I've been told).

 Rick

  Something else about these center plates, the 422 plate is out of a Cadillac distributor, which explains why it's got a really small amount of advance compared with the others. Not sure what the other plates are from.

  Rick

Alright,  I couldn't find the reason why my timing was only showing up with about 4 degrees of distributor advance, even though you could clearly see it working like it's supposed to with the distributor cap removed and a remote coil.
 So I've scrapped that method of testing, and I did some research online into building my own distributor machine and found one that looked like it would work for me. I think DJD OLDS mentioned it earlier but it sounded too complicated at the time.

 So after building it and testing everything multiple times, making some improvements as I went along, I've finally got the information I wanted for the parts I've got on hand.

 Here's a few pictures of what I built for a distributor machine, and one of the results of my testing the parts on hand.
 I only tested with the center plates installed numbers up as the factory intended, because I had tried them numbers down during the last round of tests and found that most combinations showed they didn't work nearly as well. There were a couple that looked like they would work upside down, but the time involved in testing each one I felt wasn't worth the effort.
 So I hope this will help someone down the road with making a decision on what to use if you have any of the pieces to choose from that I've tested.

  Rick

How did you calculate the LPCP for your engine?
 Rick

Here's how i did it, using my current wot and ignition timing as example:

crank rotation:  60,000 ms / (RPM * 360°) = ms/deg
4600 rpm = 0.0362 ms/deg

~12.8 afr using 87/E0 and ~90% VE (~0.5" hg) = ~1.3ms burn time to peak pressure
~0.3 ms from spark to flame propagation. = 1.6ms
Total burn from start to peak pressure = ~44.2° of rotation.

timing is set to 8° base and hard stop of 10.5° advance @ 3200 = 18.5° TA > 3200 rpm

burn time from ignition to peak pressure - spark advance = lpcp
44.2° burn - 18.5° btdc start = 25.7 atdc lpcp


-Allan

mudsport,  your's is a bit easier, so i'll respond to it first.  yeah, most 4.3 stock is 8° base to keep the timing peak around 1600 under control while giving the most power/torque to get on plane. 
you're right...it's not a race boat, i don't time it, i don't run anyone in it, and im not trying to get a street curve in the ignition...that's a sure-fire recipe for disaster.  the curves are lazy to account for the multiple variables in boats and their respective owner/operator.  since i can control some of those variables, i can account for them and reset accordingly.   i dont have room for a larger engine, nor am i looking for an outrageous output from this one.  the mileage is negligible.  dont' really care, but want it reasonably efficient and somewhat close to the 205hp it's rated for.