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New or reman distributor?By "pre-ignition," do you mean the engine knocks and keeps running when shut off (aka, dieseling, after-run)? Is there an idle solenoid on the throttle linkage side of the carburetor? Is it connected and adjusted to positively extend when the ignition is switched on and then fully and immediately retract when the ignition is switched off? What are the curb and base engine idle RPM settings that you used?With the engine running and while using a timing light, if you apply vacuum to the distributor vacuum advance does the timing advance? How much? Does the can hold vacuum? Then, with the vacuum advance disconnected, does the timing advance if you rev the engine? How much? At what engine RPM does it stop advancing?With the engine off and the distributor cap removed, can you rotate the rotor ~10° CW against spring tension? Will it return to its original position when released? Is the rotor rotation consistently repeatable by hand or does it stick/hang up?
By preignition I do mean dieseling. I managed to fix that by turning idle way down. Apparently when I replaced the distributor it somehow changed my idle speed. There is no idle solenoid on the carburetor. Curb is ~450, base is set from factory (aka I forgot to check). The timing does not advance much, maybe 2 degrees when vacuum is applied. The can holds vacuum, and was new with the distributor. Timing does advance about 2 degrees when vacuum is disconnected and engine is revved. I cannot tell what rpm it stops advancing as the interference in my engine bay is too much for my tachometer to give a good reading with engine revved, but I would guess it is about 4,000 rpm based on sound alone. The spring tension in mechanical advance seems good. It is the same as in the old distributor. Rotor seems to advance and return freely.
Quote from: bnoggle on June 15, 2017, 03:09:25 PMBy preignition I do mean dieseling. I managed to fix that by turning idle way down. Apparently when I replaced the distributor it somehow changed my idle speed. There is no idle solenoid on the carburetor. Curb is ~450, base is set from factory (aka I forgot to check). The timing does not advance much, maybe 2 degrees when vacuum is applied. The can holds vacuum, and was new with the distributor. Timing does advance about 2 degrees when vacuum is disconnected and engine is revved. I cannot tell what rpm it stops advancing as the interference in my engine bay is too much for my tachometer to give a good reading with engine revved, but I would guess it is about 4,000 rpm based on sound alone. The spring tension in mechanical advance seems good. It is the same as in the old distributor. Rotor seems to advance and return freely. If there is no idle solenoid, then curb idle and base idle are the same. Dieseling results from too much air entering the engine and/or improper ignition timing. Poor engine power can result from insufficient or poorly implemented ignition timing. W/o an accurate tachometer or timing advance light, diagnosis of the distributor timing curve can be difficult. However, two degrees vacuum advance is insufficient. Manufacturer references are available that accurately describe timing curves by distributor number and application. Unfortunately, I don't have them at my disposal. Strictly as a guess without any reference materials, I expect vacuum advance should be in the range of 8° - 16°. Mechanical advance probably should be in the range of 20° - 30°. Where is the base timing set?Remove the #1 spark plug and bring the piston to TDCC. Peer through the spark plug hole with a bright penlight or substitute a long straw touching the top of the piston to verify that the piston is at the very top of its stroke. Once you confirm that the piston is all the way up, look at the timing marks on the balancer and see whether they align to zero. This will determine whether the outer ring of the balancer has slipped, throwing the timing mark out of compliance.Did you ever check for side-play in the throttle shaft of the carburetor (see prior post)? Do you still have the original distributor?
So, when the engine runs rich the symptoms disappear. Try adjusting the base timing to 12° to see what happens.
I have also noticed in the past few days that I have an unburned gas smell coming out of the tailpipe when cold, but once it warms up and starts to shake the gas smell goes away.
Engine has been adjusted to 12 degrees before TDC. It runs better, but there is still a significant gas smell coming from the tailpipe when after the engine warms up. It also begins to shake a bit still when this happens. I tried timing to several different points and 12 degrees is definitely the best. Could it need to be an mixture screw adjustment?
Quote from: bnoggle on June 20, 2017, 10:34:08 AMI have also noticed in the past few days that I have an unburned gas smell coming out of the tailpipe when cold, but once it warms up and starts to shake the gas smell goes away.Quote from: bnoggle on June 25, 2017, 09:17:58 PMEngine has been adjusted to 12 degrees before TDC. It runs better, but there is still a significant gas smell coming from the tailpipe when after the engine warms up. It also begins to shake a bit still when this happens. I tried timing to several different points and 12 degrees is definitely the best. Could it need to be an mixture screw adjustment?Your statements are contradictory. Why? The residual symptoms sound like an engine misfire caused by a carburetor issue (wrong or improperly installed gasket, plugged passage, incorrect adjustment, etc) or bad fuel. What brand & number spark plugs did you install?