Mr. Hambone?asiab3 wrote: Continued from another thread...
hambone wrote: Best seems to be 30 deg. full advance, disconnect retard.
If I run it at 32 full advance, retard barely keeps the idle at 900.
If I run it at 28 deg. it doesn't like to idle after a run, and runs hot.
It also doesn't like to start after warm and shut off. I have to crank it a good 6-7 seconds before it catches, pedal floored "the Colin method".
When cold it runs rough for the first minute or so. I don't like it but it's the way it's been.
Hard to tell what to do, if it's the carb or the distributor. I've been chasin my tail here for a month. It seems to like higher advance...
From what i have gleaned, you have a pilot jet not seated because at some prior point, the engine would only idle with that jet turned out a crack, yes? Seat that sucker. You cannot get the balance of all of these interacting systems with any one of them compromised.
With the pilot jet seated, and the idle mixture subsequently readjusted to compensate, you will not have such a difficult warm start. You might find that this also improves your rough cold running.
IF seating the jet destroys all chances of getting an idle, you need to investigate why.
Low float level?
Incorrect main/air-correction jet?
Clogged passage?
Fluffy crap aftermarket base or top cover gasket squeezed into delicately calibrated holes?
Crushed pilot jet seat (due to overtightening) ?
Crap between the intake manifold and head (I have seen some doozies)?
I can tell if my mixture screw is adjusted incorrectly just by how the engine catches on a cold start. If it is too lean, my cold start may stall. If it is too rich, my cold start has a rough idle. If my timing is too advanced, the cold idle gets too fast before the choke shuts off. If my timing is too retarded, the cold idle has a temporary dip when the choke shuts off.
Regarding "likes more advance" vs "runs hot at 28*". Any time the timing is more retarded, you get more combustion heat dumped into the exhaust system. It only seems hotter at the apron, but CHTs show a cooler combustion chamber at relatively more retarded timing.
If we are going to attempt to control variables here, my first sacrosanct control variable is a precise valve adjustment followed by (for a SVDA or DVDA equipped engine) correct maximum advance (hoses off).asiab3 wrote: Do you remember off hand seeing the hole in your throttle butterfly plate? DVDA distributors like this hole, and some carb rebuilders (Volkzbitz if you ask him to) will solder/rivet this hole shut to make it better with a 009/SVDA.
Is your big idle speed screw cranked WAY out? Good! You have my permission to really loosen it to get an idle. As long as the screw o-ring is still stiff enough so the screw doesn't back out, 'yer fine.
Dualport Type 1 max for me is 30*, preferred 28*.
Next variable to conquer is a functioning thermostat and air preheater system.
Then, proper float level, correctly indexed carburetor gaskets, proper jets, etc.
To test the vacuum retard range, you should do a temporary timing adjustment at idle to 7.5* just to see that the vacuum can can pull it down to 5*ATDC. Some advance cans have migrated from the dual carb buses into general circulation, they have a more intense pull down to 10* ATDC.
Colin