1968 Newport 383 2V Tune up Specs?

[MBar]

Not knowing any better and pre-forum, I had set timing to TDC. Seemed to run fine. have a few hundred miles since then and now it's missing a bit and real soft backfire when cruising and I let off the gas. This morning I found a "maybe" loose plug wire (driver rear) but I figure I want to get the tune correct.

Heading to get a tach and gonna tune her up...any other tools beside a timing light and feeler gauge?

Question1: Should I buy a dwell meter? or just adjust the points?

Question2: Suggested RPM?

Question3: Difference between the two idle screws?

Question4: What should the timing be set at?

Question5: When I turn the mixture screws, one has no effect...Guess a carb rebuild is next but not today so what do I do with that screw for now? I know not to tighten it too much to avoid damage

Tried the FSM but for some reason it's not clear to me and I am hoping someone can give me a quick step by step.
As always, thank you for all assistance




Regarding the timing, lately

 

[Davea Lux]

Not knowing any better and pre-forum, I had set timing to TDC. Seemed to run fine. have a few hundred miles since then and now it's missing a bit and real soft backfire when cruising and I let off the gas. This morning I found a "maybe" loose plug wire (driver rear) but I figure I want to get the tune correct.

Heading to get a tach and gonna tune her up...any other tools beside a timing light and feeler gauge?

Question1: Should I buy a dwell meter? or just adjust the points?

Question2: Suggested RPM?

Question3: Difference between the two idle screws?

Question4: What should the timing be set at?

Question5: When I turn the mixture screws, one has no effect...Guess a carb rebuild is next but not today so what do I do with that screw for now? I know not to tighten it too much to avoid damage

Tried the FSM but for some reason it's not clear to me and I am hoping someone can give me a quick step by step.
As always, thank you for all assistance




Regarding the timing, lately

1.) A dwell meter is nice to have to verify that you have set the points correctly. A lot of the modern ones have both a dwell and tach function built in. Set points to .016-.019 with a feeler gauge at the top of one of the distributor lobes.
2.) 600 to 650 RPMs at idle is usually a good place to start, A/C cars may need slightly higher settings
3.) Both idle screws should be set to the same number of turns from fully closed position, start at 2 1/2 turns and adjust from there.
4.) Timing is 7 1/2 degrees before TDC on auto equipped engines. Set at TDC for manual transmission.
5.) Set plugs to .035

These are factory specs for timing, these engines will usually need to be tweaked slightly to run correctly on today's moonshine blend fuel. The best way to do this is with a vacuum gauge hooked to manifold vacuum. Increase timing by rotating the distributor until the vacuum pressure no longer increases with the timing. Lock the distributor down and note the position of the engine timing with a timing light. Test drive the car, if excessive pinging is noted, back off the timing in 2 degree increments until the level of pinging is acceptable. Record whatever number of degrees of Timing you end up with for future reference.
Tune up specs are in Section 8 of the FSM under specifications.

Dave

 

[PurpleBeeper]

Dave is giving you some good advice. For my 2-cents....
1. I always set my point with a feeler gage (like Dave says, make sure the points are on top of one of the "bumps")
3. The idle mixture screws are for each side of the carburetor. You most likely have one side blocked with old fuel "varnish". I've "heard" that sometimes you can clear out that varnish by spraying carb cleaner up into the hole where the screw goes, but it has never worked for me & I had to rebuild the carburetor.
4. I've always had the best luck at 10-12 degrees initial advance. Like Dave says, set the timing with the vacuum advance hose disconnected & blocked off. After setting, drive the car to warm it up & then try some full-throttle or accelerating up a hill and listen for any little rattle. If you hear any rattle, retard the timing until you don't hear it any more.

 

[MBar]

Dave is giving you some good advice. For my 2-cents....After setting, drive the car to warm it up & then try some full-throttle or accelerating up a hill and listen for any little rattle. If you hear any rattle, retard the timing until you don't hear it any more.

I was about to ask how I can tell when it's pinging.. thanks!

 

[MBar]

1.) A dwell meter is nice to have to verify that you have set the points correctly. A lot of the modern ones have both a dwell and tach function built in. Set points to .016-.019 with a feeler gauge at the top of one of the distributor lobes.
2.) 600 to 650 RPMs at idle is usually a good place to start, A/C cars may need slightly higher settings
3.) Both idle screws should be set to the same number of turns from fully closed position, start at 2 1/2 turns and adjust from there.
4.) Timing is 7 1/2 degrees before TDC on auto equipped engines. Set at TDC for manual transmission.
5.) Set plugs to .035

These are factory specs for timing, these engines will usually need to be tweaked slightly to run correctly on today's moonshine blend fuel. The best way to do this is with a vacuum gauge hooked to manifold vacuum. Increase timing by rotating the distributor until the vacuum pressure no longer increases with the timing. Lock the distributor down and note the position of the engine timing with a timing light. Test drive the car, if excessive pinging is noted, back off the timing in 2 degree increments until the level of pinging is acceptable. Record whatever number of degrees of Timing you end up with for future reference.
Tune up specs are in Section 8 of the FSM under specifications.

Dave

So...as I stand at the front facing the car, advance shows the line to my left or right of the mark on the timing cover?

 

[Davea Lux]

So...as I stand at the front facing the car, advance shows the line to my left or right of the mark on the timing cover?

Engine rotates Counter Clockwise, to the left. The timing cover should have a scale on it, usually covered with grease that has the TDC and Factory timing indent marked on the scale.

Dave

 

[MBar]

Engine rotates Counter Clockwise, to the left.

Dave

So as I advance the line on the balancer will be to the left of the mark on the cover right? Sorry I'm a little dense today

 

[Davea Lux]

So as I advance the line on the balancer will be to the left of the mark on the cover right? Sorry I'm a little dense today

Yes

 

[PurpleBeeper]

So as I advance the line on the balancer will be to the left of the mark on the cover right? Sorry I'm a little dense today

And another easy way to remember.....when you advance the timing, the idle goes up....when you retard the timing, the idle goes down.

"In general" more advance is better, but if you start to hear a tiny little rattle under the hood when you floor it (aka "knock" or "ping") that's really bad. So.....just advance the timing until you hear the rattle & retard it back a little until the rattle is gone.

Fyi-I am grossly over-simplifying this, but on a relatively stock motor, this will work for you. I don't think you need to go into vacuum vs. no vacuum advance, mechanical advance limiting or lock-out distributors, re-curving mechanical advance, etc.....what's above will do the trick.

 

[Gerald Morris]

1.) A dwell meter is nice to have to verify that you have set the points correctly. A lot of the modern ones have both a dwell and tach function built in. Set points to .016-.019 with a feeler gauge at the top of one of the distributor lobes.
2.) 600 to 650 RPMs at idle is usually a good place to start, A/C cars may need slightly higher settings
3.) Both idle screws should be set to the same number of turns from fully closed position, start at 2 1/2 turns and adjust from there.
4.) Timing is 7 1/2 degrees before TDC on auto equipped engines. Set at TDC for manual transmission.
5.) Set plugs to .035

These are factory specs for timing, these engines will usually need to be tweaked slightly to run correctly on today's moonshine blend fuel. The best way to do this is with a vacuum gauge hooked to manifold vacuum. Increase timing by rotating the distributor until the vacuum pressure no longer increases with the timing. Lock the distributor down and note the position of the engine timing with a timing light. Test drive the car, if excessive pinging is noted, back off the timing in 2 degree increments until the level of pinging is acceptable. Record whatever number of degrees of Timing you end up with for future reference.
Tune up specs are in Section 8 of the FSM under specifications.

Dave

This is EXACTLY what I wound up using for my tuning procedure on Mathilda. Timing is about 10 degrees BTDC and she purrs along. Curb idle is ~550 rpm when warmed up. VERY SOUND ADVICE here.

 

[MBar]

I went with 7.5 and it runs great...but when I shut it off, I sometimes get "dieseling".. I think that's the correct term for "it still runs a moment after I shut off".
is that an indication of too advanced or not enough? I also noticed my carb is pretty dirty and a rebuild will be soon

 

[Davea Lux]

I went with 7.5 and it runs great...but when I shut it off, I sometimes get "dieseling".. I think that's the correct term for "it still runs a moment after I shut off".
is that an indication of too advanced or not enough? I also noticed my carb is pretty dirty and a rebuild will be soon

Most of the time, you can cure dieseling with some minor adjustments. If you have the carb idle screws set a tad too rich, that can cause dieseling. Plugs that are too hot of a heat range can also cause dieseling. Idle speed set to high can also cause dieseling. A carb that has an internal fuel leak, such as a bad needle valve or an incorrect float adjustment can also cause dieseling. A engine that is running too hot can also cause dieseling. Sometimes just shutting the car off while it is still in gear will prevent dieseling. Timing that is way off can cause dieseling, but at 7.5 degrees, that is not likely your problem.

If you think the carb needs to be rebuilt, that is as good a place to start as any. Get it back to factory specs and see what happens.

Dave

 

[PurpleBeeper]

Davea Lux really has a lot of good detail in his post. "Most" of the time I've had this problem it was the idle set too high (specifically, the idle screw turned in too far).

You may want to try to get the engine warmed up fully, turn the idle screw down (screw out) until the engine is barely running, then try to increase the idle back up (using a vacuum gage) by adjusting the idle mixture screws, one side at a time, maximizing both engine vacuum & idle rpm.