Question about timing a 69 RR 383

[HALIFAXHOPS]

Yes he was, good teacher though.

 

[Cranky]

Yup, lots of variables....and what an engine likes is based on the combination of the engine and other things. For example. I've found that low compression engines (usually have low cylinder cranking pressure) like more timing both initial and total than higher compression engines. Test drives can be very helpful.....

Gotcha. I just always seem to end up all alone when messing with timing.

Same here. Been a one man band for many years due to shift work etc and got used to doing most everything alone and these days, when there is help around, we usually end up running into each other.....a lot lol.

 

[BSB67]

 

[diesel_lv]

So what do I do when I hook up the vacuum advance? Will that be OK?

Temporarily run a long vacuum line from the carburetor ported vacuum port to inside the car without pinching it and hook up a vacuum gauge. Drive the car on the highway and see what your normal vacuum is at interstate or local highway speeds. Then disconnect gauge. If your distributor vacuum pot has an Allen head adjustment inside the tip, then it should be adjustable. Remove distributor cap and find the flat rod that goes into the vacuum pot. Connect a mighty vac pump to the vacuum pot and slowly pump until you see the flat rod start to move. Record that number. I set my vacuum pot to start moving, adding timing, about 1-1/2" vacuum below my normal cruise vacuum. Put Allen key inside and turn 1/4 turn either way, recheck w vacuum pump and see which way vacuum went to make flat rod move. Then adjust it for your highway cruise vacuum. For me in the very hot, 120°, desert, I need the vacuum advance gone almost immediately when I press the accelerator to avoid detonation. Other areas are different depending on heat, compression, type of fuel. This is how I set mine for 120°, 10.5:1 and crappy west coast 91 octane.

 

[hunt2elk]

You need someone inside to look at the tach.

My timing light has a tach built in, so I am all set in that regards.

 

[69a100]

Wow, Frieburger was young on that video.

Must have been back when he had some brains, why's he wearing a jacket inside? You'd never see that today! All I ever see him in is T-shirt, shorts, & flip flops. Even in Alaska with snow on the ground, what a putz!! I'm just waiting for him to drop a motor on his almost bare foot someday!!!!!!

 

[mpro69rr]

Temporarily run a long vacuum line from the carburetor ported vacuum port to inside the car without pinching it and hook up a vacuum gauge. Drive the car on the highway and see what your normal vacuum is at interstate or local highway speeds. Then disconnect gauge. If your distributor vacuum pot has an Allen head adjustment inside the tip, then it should be adjustable. Remove distributor cap and find the flat rod that goes into the vacuum pot. Connect a mighty vac pump to the vacuum pot and slowly pump until you see the flat rod start to move. Record that number. I set my vacuum pot to start moving, adding timing, about 1-1/2" vacuum below my normal cruise vacuum. Put Allen key inside and turn 1/4 turn either way, recheck w vacuum pump and see which way vacuum went to make flat rod move. Then adjust it for your highway cruise vacuum. For me in the very hot, 120°, desert, I need the vacuum advance gone almost immediately when I press the accelerator to avoid detonation. Other areas are different depending on heat, compression, type of fuel. This is how I set mine for 120°, 10.5:1 and crappy west coast 91 octane.

I will keep this in mind, I am not ready to drive it yet because I don't even have the steering wheel installed! lol

 

[65-440]

LOL new math. Where ever you set the initial you add the total mechanical to it. Starts as a negative number then past 0 and final result is positive if that makes sense. -10 +30 = 20

What in the F? Totally screwed me up on that one! ...it's all BTDC, where's the positive # coming from? .....come to think of it, why is After TDC even on the tape/balancer? Who the hell uses that side?!!

 

[HALIFAXHOPS]

I tried

 

[BSB67]

 

[1967coronet]

So I have -18 initial now, that means I would add another -18 to get -36 total?

No, 1st thing is to open up the distributor and see what number is on the plate.
That is on the bottom advance plate. It will be stamped with a number. That number is 1/2 of your mechanical advance.
In my case I have a 9.5 number. That's a 19 degree plate.
Now for a 36 total I can set my initial at 17 with the can unhooked and the vac line plugged off.
Your rate of advance or ( were it comes in ) is controlled for the most part by the small springs on the inner weights under the inner plate.
The lighter the spring the distributor will advance its mechanical at a lower rpm.
That is test and try to find out what your engine operates best at.

 

[Don Frelier]

What in the F? Totally screwed me up on that one! ...it's all BTDC, where's the positive # coming from? .....come to think of it, why is After TDC even on the tape/balancer? Who the hell uses that side?!!

I think that the ATDC marks are a byproduct of points. As the points get older and develop arc spots and if the rubbing block wears they don't open as far and the timing becomes retarded. So it's possible to put a light on the car and see the timing go late.

 

[toolmanmike]

I think that the ATDC marks are a byproduct of points. As the points get older and develop arc spots and if the rubbing block wears they don't open as far and the timing becomes retarded. So it's possible to put a light on the car and see the timing go late.

Timing does not effect dwell but dwell does effect timing. You might loose a degree or two with wear but not enough to go "after top dead center". If the points were that worn the engine probably wouldn't even run.
Many stock specs are close to 0 or after top dead center especially CAP cars (clean Air Package)

 

[Billccm]

I thought during the early days of emission controls timing was retarded slightly. I recall reading that the spark at 0 or 1 to 2 ATDC reduced pinging from low octane unleaded and created a burn that reduced oxides.

 

[Billccm]

On a precomputer carbureted car, one way to get under the HC and CO limits is to retard the ignition timing. This will slow the idle and provide a longer, hotter burn.

 

[BSB67]

Timing does not effect dwell but dwell does effect timing. You might loose a degree or two with wear but not enough to go after top dead center. If the points were that worn the engine probably wouldn't even run.
Many stock specs are close to 0 or after top dead center especially CAP cars (clean Air Package)

View attachment 1106424

Going from memory, I though that some stick shift cars were factory spec.ed near zero as well.

 

[hunt2elk]

On a precomputer carbureted car, one way to get under the HC and CO limits is to retard the ignition timing. This will slow the idle and provide a longer, hotter burn.

Curious, if the timing is retarded, wouldn't that make the engine run hotter than it should?

 

[toolmanmike]

Curious, if the timing is retarded, wouldn't that make the engine run hotter than it should?

Possibly but not enough to cause overheating.

 

[69a100]

Sorry but that is just incorrect. It's always negative you are going further BEFORE TDC as you add advance.
For example you start at -10 initial add 26 more centrifugal as you speed up the motor and advance to -36 Before Top Dead Center.

Funny how quickly people forget simple math! Adding anything to a negative number gives you a bigger negative number!

 

[BSB67]

Man, I'm so enjoying this thread.