Timing

[Anonymous]

I'm trying to set timing on my 67 mustang 200 with autolite 1100 carb, stock distributor with points and Hooker headers. What RPM should it be when ajusting the timing? Do I need to be in Drive or Park when I do this? Also do I need to disconnect the vaccum line to the distributor/why? When I try to set the timing at about 1000 RPM in park, it jumps around sometimes. Why is it not consistent on the mark? Would it help if I can to a pointless distributor? I'm trying to correct some rough idle when at a stop around 600 rpm in drive. Sorry, I have so many questions.

 

[rbohm]

8) richen the idle mix and bump the idle speed a bit. that should cure the rough idle. if not then bump the timing a couple of degrees.

 

[CobraSix]

Sounds like you have several issues.

First, timing should be set at around 550 RPM in park/neutral. If it is bumping around a little bit, them more to your carb. It may stumble a little bit here and there, but shouldn't be very often.

To fix the rough idle:

First set your idle speed using the screw on the back of the carb on the drivers side (NOT the choke screw, the one forward of it). That is the throttle plate screw. Adjust it until you are close to your idle speed.

Then go to your idle air/fuel mix screw on the passanger side of the carb. Using a tach (or your ear), start to richen the mixture by turned the screw counter clockwise. Keep rotating the screw until the RPMs drop. Now go the other way (clock wise). Count how many turns you make until the RPMS start to drop again (they will go up somewhere in the middle). Take the total number of turns and divide it by two and turn the screw back out that many turns (usually only like 1/2 - 1 turn). That will put you at the best idle air mix. YOu could either be too lean OR too rich at idle if you have a rough idle.

If you find your RPMS have changed above or below where you want them to be at for idle, repeat the process. I would advise to check your timing and make sure it is still set before you repeat. Also check you 3000 RPM timing and make sure it is correct at around 32-36* BTDC. Then redo you idle speed setting.

Slade

 

[CZLN6]

Howdy Umsam:

And you need to disconnect the vacuum line from the carb. If you don't you will get a timing light reading that includes vacuum advance. You want initial only, to set the timing.

Before during or after you would be wise to thoroughly clean your carb, inside and out, to get the most out of it. Spray down the inside and outside with carb cleaner, and put a can of fuel system cleaner in the gas tank. also change your fuel filters. Nest, make sure that your PCV valve is working as it should. These items can effect carb performance, especially a smooth idle.

Now that you have a clean carb, idling at the lowest rpm possible with the trans in "drive", and your initial timing is set, with the trans in "Park"- turn off the engine and either suck, or apply a vacuum pump to the rubber vacuum line that goes from the carb to the distributor vacuum can. Watch for the vacuum advance arm to move. If you see it move, you will know that the vacuum advance is working. If it doesn't move you have a problem with vacuum advance. Assuming all is working correctly, don't forget to reinstall the vacuum hose to the carb and the distributor.

If you are not getting vacuum advance, it could be either the Spark Control Valve on the Autolite 1100 or the vacuum canister on the distributor. A new SCV is in a carb rebuild kit- a good excuse to rebuild the carb. The best way to repair a bad vacuum cannister is to upgrade to a later distributor and vacuum cannister, '68 to '72 for points, or '76 and later for electronic. The plus of the later distributor is that you will gain mechanical, or centrifugal advance, in addition to vacuum advance. You will be amazed at the difference a late model distributor and clean carb make for a smooth quiet idle.

Adios, David