Clay, you are correct about the way the timing light functions. I have a couple of them, they are very handy. I do believe your problem is carb related. I have a friend with a brand X motor and his complaint was surging at cruising speed and a slight hesitation just off idle. Changed two sizes larger on the main jets and both problems are fixed. I am running a 312 with initial timing of 16 degrees, also have a new demon carb that came with .058 mains. Idle was terrible at first and I had a large flat spot off idle. Changing mains to .062 cured about 90% of the off idle problem and I have been driving that way for awhile now. Just change the mains to .064 and boy what a difference! Hesitation is 98% gone, idle picked up 150 RPM (most people think main jets don't affect idle but they do), but most importantly the engine pulls much stronger at low RPMs. I think with a little more tweeking it will run perfect.

The only probem I can see with changing the ignition is you are introducing a new variable. If you do so I would run the car before and after installation with NO OTHER chages made so as not to confuse matters.

Mike

1956 Fairlane Victoria (ORREO)

 

Overlooking Beautiful Rimrock AZ

Duck,



The fuel pump is new. That being said, I guess proving its capabilities remains a valid suggestion.







Steve,



I understand. My Ford shop manual states the grooves in the pulley represent 2 degrees per grove, thus the 4th or 5th grove above the TDC groove should have me at 8-10 degrees of initial Advance.



Then I think I could then prove the timing gun as being accurate two different ways:



1. It should read "0" on the display with the 8-10 degree groove lined up with the pointer.



OR



2. Advancing the up arrow to 8-10 degrees in the timing light display should then show the TDC mark lined up with the pointer.





Mike,



I will hold off making any further additions until this problem is rectified. I guess main jets will be the next item to focus on. Further up this thread I mentioned that I noted the carb has a #31 discharge nozzle installed. While I'm ordering new jets, do you guys think I'm in the right ballpark with the #31 nozzle?



PS Beautiful car!

pops (AKA) Clay

'56 Thunderbird

I still recommend testing the vacuum advance diaphragm. A leaking advance will cause the timing to fluctuate a cruise and create a tip-in hesitation. Very simple test and a helluva lot easier than digging into a carb without knowing if the ignition advance is malfunctioning.

57 Black Tbird 312/auto

Mark,



I've been sitting here thinking on what I might have around the house to create a vacuum to perform the test you mentioned. I think I have it if I can develop enough. I'm going to give it a try as soon as I change.

pops (AKA) Clay

'56 Thunderbird

Hillbilly vacuum advance test procedure. Remove the distributor cap. Look at the arm that comes through the side of the distributor body and make sure it is free by pushing the arm back with your finger or suitable hand tool. It should rotate the distributor breaker plate a quarter inch or so. Attach a rubber vacuum hose to the carb end of the advance line and then by oral means, apply a sufficient vacuum on the line going to the distributor advance and pinch off the line with some needle nose pliers. Watch to see the arm move when you apply vacuum and that it doesn't bleed back into position. Releasing the pliers should cause the arm to return to the original position. If the arm doesn't move or moves then bleeds back down the diaphragm is leaking.



Non-hillbilly vacuum advance test procedure:



Substitute a proper tool for the job:



http://www.craftsman.com/shc/s/p_10155_12602_00920930000P?keyword=vacuum+pump&prdNo=2&blockNo=2&blockType=L2



If it needs replacing, Napa Auto parts has them for 57 Tbirds, Part#ECH VC945 $31.95 and be careful removing and replacing the chingadera clip that holds the arm to the breaker plate.

57 Black Tbird 312/auto

Do your carb float levels.. When you have sorted and car is running ok change to the Pertronix 2 it has variable dwell and a much better unit. If you have the matching flamethrower .06 ohm coil even better. You wont need the ballast just make sure you have the full 12 volts there and it will run like a champ.



"Came too close to dying to stop living now!"

Both the vacuum and centrifugal ignition advance systems can be checked with the timing light.  Simply observe the timing marks at the damper with the timing light while running the engine at various rpms with the vacuum hose both connected and disconnected.  If there’s no change in the rate of advance between the hose being hooked up and not, then make sure the hose itself is clear and is hooked up to a suitable vacuum source.  When in doubt about the ported vacuum, hook the hose up to ‘direct’ vacuum source on the intake manifold to verify vacuum pot operation with a timing light.

Lorena, Texas (South of Waco)

I performed the static timing procedure and it was within a degree or two of what the timing light showed.



16 degrees initial seems to be the sweet spot.

With 16 degrees initial, the advance reads 24 degrees @ 2500rpm (centrifugal only)

and 44 degrees @ 2500rpm when the vacuum advance is introduced.



I'm convinced the timing is as close as I am able to achieve. I too think it is time to go on to the carburetor. Problem is I may well run out of time before I need to move the car. I have to leave town today and gone for the week. That leaves me with two weekend windows to get the car to Cleveland. I need to go the first weekend that the weather looks good. So, I may have to wait a little while until I can get the carb off to look at the float settings and see what jets are in it in order to up size a couple of sizes to see if this will make a difference in the stumbling. Jury is still out on the pump although it was to have been a new pump when I purchased the car in October.



(Best Arnold voice)



"I'll be back."

pops (AKA) Clay

'56 Thunderbird

Do you only have 8 degrees of mechanical advance (24 - 16 = 8)? Is 2500rpm the point at which it stops advancing?



Lawrenceville, GA

Charlie,



I only recorded the advance readings at idle and at 2500 rpms. I guess I should I go to the point the centrifugal and vacuum max out to determine the total advance.?

pops (AKA) Clay

'56 Thunderbird