Timing on 69 350/350

[Thomas Christopher]

Is anyone running the recommended 4* BTC? I tried to set mine at that setting this past weekend, and the car would hardly run with that setting at 750 rpms.

I'd just accomplished a tune up, and when I checked the timing, it had been set at about 15* BTC (est), so I adjusted it down. That's when the idle problems began. Someone help me out here.

Tom

[Joe L.]

Re: Timing on 69 350/350

Thomas------

The engine should run nicely at the recommended setting of 4 degrees BTDC and idle speed of 750 RPM. You may be able to run more advance to advantage, but it should still run fine at the factory-published setting.

I would expect that some sort of modification has been made to the engine which may affect its ability to operate properly at the factory-recommended idle and timing settings.

[Duke W.]

Re: Timing on 69 350/350

The ignition timing map for your L-46 is set up for emission control. If you do not have to have the car emission tested, my recommendation is to recalibrate the dist. to '65 SHP/FI specs beginning with replacing the vacuum can with a MAPA/Echlin VC1810, which starts at about 4" and provides 16 crankshaft degrees at 8". Also, and this is very important, plumb the vacuum can signal line to a full manifold vacuum source as I believe your engine has a "ported" vacuum source for the vacuum advance that does not allow manifold vacuum to reach the can at idle and very low throttle openings. The VC1810 vacuum can connected to a full manifold vacuum source will ensure that you have full vacuum advance at idle.

I don't have the specs for your centrifugal advance, but set the initial timing so the sum of initial and total centrifugal is 36-38 degrees. The initial timing much be set with the vacuum advance disconnected and the engine operating at a low enough speed to insure that the centrifugal in not deployed.

The basic rule of thumb is to get the centrifugal in as quickly as possible, but low speed detonation may set a limit on how aggressive the curve can be. On cars that have a faily aggressive curve - say the centrifugal is all in by 3000, I prefer to set total timing by revving the engine to 3000 plus and setting the total to 36-38 using an accurate dial back timing light or timing tape on the balancer. As with the initial timing setting, this must be done with the vacuum can disconnected.

Once the total initial plus centrifugal timing (what I call the "total WOT timing") is set, rev the engine to 6000 while observing the mark to verify that it doesn't not overadvance. Once your ignition map is modified you must retune the idle speed and mixture, and use the method applicable to pre-emission cars. - that is, set the mixture to achieve the highest manifold vacuum/engine speed.for a given idle speed screw setting.

Duke

[Jack H.]

Have seen....

a few isolated instances where the harmonic balancer was starting to 'go' and the outside timing mark had 'slipped' causing readings with strobe to be WAY off...

[Thomas Christopher]

Timing on 69 350/350

Thanks all.

The engine was rebuilt before I bought it, and the guy who had it rebuilt said it was rebuilt with a little extra HP. Also my emissions stuff was long gone before I bought it. Hope this additional info helps you guys point me in the right direction.

Tom

[John H.]

Re: Timing on 69 350/350

Tom -

Since you're not sure of the innards (or what vintage balancer may be on it, which matters a lot), I'd start with basics first and use a piston stop tool to verify that actual #1 TDC shows as TDC (or doesn't) between the balancer index line and the "0" mark on the timing tab. Then you'll know what your baseline is, and from there it's a matter of distributor and vacuum advance calibration.

[Dave Suesz]

Rubber ring problem can be repaired....

Contact Glazier's Mustang Barn.

[Roy Braatz]

Re: Timing on 69 350/350

When I was a kid having no money for a fancy timing light we would time our cars by ear.
Loosin the dist. run the engine up by hand to about 3000, move the dist back and forth till the engine ran smooth, then have the dist lock nut just tight enough so that it would stay, drive the car hard, stop and advance the dist a little , stop and do it again till it pinged a little ,then retard the dist a hair . We found that the car always ran the best useing this method and I still do it that way today and found it works great.Try it , you'l love it and don't have to worry about degrees and markings.

[George Romano]

Re: Timing on 69 350/350

I did it that way for years Roy! Great tune for the dragstrip, but the open headers at 3K with your melon under the hood was a bit much after a while!

George

[Roy Braatz]

Re: Timing on 69 350/350george

You have to speak up.can't hear to well ...Been there done that too.