redlightrich

iTrader: (1)

Hello all, I have a SA that I decided to keep near original based on it's condition. All underhood items are present and accounted for.

I did make 2 major changes though, which may play in.

1) I changed the distributor from the points type to one for a later 12a that is electronic.
2) I changed the trans from Automatic to a 5 speed, and I used a RB lightweight steel flywheel and a LUK clutch assy. The factory flywheel is way way heavy!! I believe the RB is 17lbs. It is not the super light aluminum one.

I have new coils, plugs, cap, rotor, wires, battery and filters. I have covered my basics. Timing is set at the factory spec, both leading and trailing.

I have just drained the tank, fresh fuel and filter, and I "rebuilt" the carb, in which I found a few problems by a previous owners mechanic.

Anyway, after doing my best to tune this, it idles exceptionally well. It starts easy whether it is cold ( NJ Winter at 15 degrees) or hot motor. It also now accelerates very well. It easily revs to red and pulls very strong. I feel as if I could wind it up to 8000 rpm with no effort, but I don't want to harm anything.

My issue is there is a slight surge present at steady cruise speeds. The RPM indicate 28-4000 rpm when I feel it. If I accelerate, it is not evident, and my throttle response is excellent at all RPMs regardless of whether the surge is present or not.

If it is a vacuum issue, it will be ported vacuum, as it is perfect at idle. The air bypass screw and mixture screw react perfectly when tuned. If there were a manifold vacuum leak, it would more than likely affect these adjustments in a negative way.

I have not driven the car for any real length of time since I have owned it. At first, it was so bad that driving it was not enjoyable, especially when it was an auto. It now runs better than it ever has, but the surge prevents it from being "perfect".

If there are any tricks or something I overlooked, I will greatly take the feedback. I have tried moving the timing to a more advanced position ( up to 20 degrees advanced!) and it has no impact on the surge. I put the timing back to factory ( line up the marks at idle).

I have the idle set at 775 rpm, factory is 750. I don't think the extra 25 rpm makes too much difference here .

My bud, who has helped me with some of these projects on the car said " drive it for a while and see if it clears up". He did note, the low mileage means it sits often. I have had it for 2 years and barely put 100 miles on it, so it sure does sit. If the carb is ok, then what can sitting contribute to a surge issue? Remember, the fuel and filters and carb are now fresh. Please help me enjoy this car right. I promise to drive it more if it runs well!!!!

Rich

t_g_farrell

iTrader: (1)

It could be your dizzy is not running true or your fuel pump surging. Just guessing.

redlightrich

iTrader: (1)

Thank you for the reply. I guess I can check both those items. I can hook up a fuel gauge and monitor it at cruise, and I can shoot the timing at multiple RPM ranges, but this won't reproduce a load. I guess I need to start somwhere.

Thanks again

rwatson5651

iTrader: (5)

I would suggest checking the vacuum and mechanical advance on your distributor.

as an experiment you could temporarily advance your timing about five degrees or so and go cruise and see if it affects the surge.

t_g_farrell

iTrader: (1)

I remember someone on the forum having an issue like this and their dizzy shaft was not true and it
wobbled affecting the firing and timing.

marclong

iTrader: (1)

Could be the accelerator pump in the carb. Mine has the racing beat holley carb and changing to the white accelerator cam has mostly solved the same symptom you describe. Not sure on the nikki carbs if that is adjustable.

7aull

iTrader: (2)

While I leave the specifics of your problem to the Pros here, I will suggest that if indeed it is driven so little, you will need to make some investment in correctly storing the car between uses. 100 mi (or even 20) in one drive is fine for getting the engine up to temp and burning off any water condensation in the engine or exhaust, etc. But sitting untouched for much over say, 2 months and you will likely have all sorts of niggily issues popping up. For one, most fuel doesn't "store" well in a gas tank for months, so a stabilizer will help.

Older cars like ours do not do well to sit.

Stu Aull
80GS
Alaska