Not at all. Most of the thread is right; timing chain wear, distributor wear, and any number of other things can change initial and total timing with the hold-down bolt never having been touched. Broke spring on the centrifugal weight can bring total initial timing on early, pinhole leak in the vacuum line for the vacuum advance can lessen total advance, very worn chain can slip a tooth... And that's not mentioning carbon buildup in combustion chambers that can raise actual compression ratio, which will "change" thew timing, but actually make the engine need less advance to not ping, or blowby that can require more timing to mkae the same power as a new engine. For old cars, the factory specs re: timing are really more a guide than absolute canon. See what yours likes; I once had a Dodge Diplomat that was supposed to be 6-7 BTDC, and would only run right with about 1-2 ATDC.

Most of the folks Around Here time by ear, anyway.... Bump it around til she starts easy, then power time to JUST before you get pinging. By "power time" I mean go make a couple hard accelerations, noting carefully if you have any spark knock. If no, SLIGHTLY turn the distributor in the opposite direction the rotor goes in. Repeat til you get pinging, then back off til it just disappears.

 

I can't seem to get the timing right on my '86 351W-HO. I believe I may have carbon buildup on the pistons, that is causing my problems. The old truck has 165,000 miles on it.
Is there cleaner, that could be injected into the carb( while running) that would remove carbon from the tops of the pistons?
The truck can be timed with a light, but ,at that setting, won't start when hot. If I set it to start hot, it doesn't have much powerand poor performance. I have changed the timing chain and have a rebuilt distributor.
I have plyed with the timing for several months, but, on occasion, have hard starting when hot. The battery,cables,starter ,solenoid and flex plate are new.

 

Thread moved to " General Automotive Discussion" due to being a general automotive question.

 

Isn't it true that if the distributor holddown screw has never ever been loosened, the ignition timing will never change?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

FALSE,

The timing changes on its own as the parts wear.

I drove my truck with the 400 until the timing would not allow the engine to run anymore.
Timing Gears & Chain wear !

 

Bdox, in the old days of cars with carbs, they had points instead of electronic ignitions. Anybody remember points? If you replaced the points it would alter the timing. You had to set the gap or dwell angle of the points and reset the timing, because it would off.
Ed G

 

Points, now that is something I had tried to forget about. How many of you always carried a point file in the glovebox? How about always having a book of matches to set the points with? Man I really like electronic ignition. LOL

 

Sure I remember points. I remember putting them together before they were sold a point 'sets,' especially the English sports cars. What a mess, all the bits and pieces that you had to assemble. If you didn't really understand exactly how the ignition worked you would never get the various parts put together in working order. I also remember having to convince other mechanics that there was no longer going to be a dwell angle reading on inductors and reluctors.

But my question was strictly Ford electronic ignition. How does it detect TDC, not having a crank sensor?

 

it uses a magnetic pickup inside the distributer. senses each time the metal fin passes in front of it

 

Yes, but that does not provide and absolute zero because it moves when the distributor is turned. I seems to me it should sense crank position directly in order to provide a fail-safe TDC. Is there any such mechanism? I'm missing something here.

 

Is this the kind that you unplug the jumper and set the base timming with a timming light? If so isn't that setting the absolute zero?

 

theres a tool you can put inside of the cylinder.You screw it into the spark plug threads. When the piston reaches TDC it starts to point up. Thats how we time radial engines anways...

 

From all I have found so far, the duraspark relies on the distributor position that you set and has no way of knowing where TDC is. It that all there is to it?

 

is the battery big enough?? my 66 7 litre would not start hot for anything. put a bigger battery in it, and it now turns over as good at 220º as it does cold.

 

another thing that can change the timing is replacing the cap and rotor.
they are not all identicle, even though parts sellers will tell you they are.
i have seen timing changes of up to 4º just by changing the cap and rotor.

as far as points go, the best thing ever invented was the pertronix ignitor.

 

bdox,

that is it nothing more.