Spark Problem

Larry in Ark.

Larry in Ark.

Junior Member
Hi, Helpers!
Need more help please :(! My problem is that when I fully advance the spark rod, it runs rough and pings (rattles) and vibrates. With it fully retarded, it idles fairly well -- no noise or vibration! It starts to make a difference at about 9 o'clock on the quadrant.
Timing is right on, points set at a tight .020. New distributor shaft, bushings, cam and rotor. The compression is good. To me, it acts like the timing is advancing too far. No, the distributor body hasn't been cut out. It starts good, in fact I don't think the flywheel turns over a 1/4 turn and it fires right off. Haven't tried it yet, but was wondering if it could be the fuel (87 octane) with a 10% ethanol blend.
Anybody else had this problem? (I hope so because I'm sure not having any fun!) :eek:
 
What's your compression ratio?
What's your compression while cranking?
Could you be using too hot of a heat range spark plugs?

My 28 with stock head and only 50 lbs. compression would also ping with very light acceleration, and I found it was due to a hot spot in the cylinder, which was caused by a buildup of rust flakes around the rear cylinder. After 30 days of the vinegar treatment I no longer have pinging.
 
Sounds normal to me.. I really can't see where these motors need 40º of ignition advance.. Every car seems to have its own 'sweet spot' which you need to find.. I never run full advance,, I run in the 8:30 to 9:00 position.. It'll run at full advance,, but,, it doesn't like it very much and even at that it doesn't ping/spark knock/detonate.. After awhile you will be able to 'feel' what it likes and dis-likes..
 
I agree with Patrick. I don't see where you would want to run the engine with the spark fully advanced. Play with it and you should soon find where your engine likes it best. The higher octane fuels do help prevent pre-ignition (pinging) but really shouldn't be necessary.
Dave
 
Larry,
mine tends to vibrate and sounds rough with it fully advanced at idle speed. At most stops, I fully retard and pull it down half way as I start to leave the intersection. Any speed above 40, I go fully advanced.
 
I've only seen that occur once. My buddy timed his car exactly as I taught him. However it turned out what he was sure was the dimple in the timing gear was not. He had it at least 15 degrees advanced. It was surprising he got as close as he did as the "false dimple" could have been anywhere!

Did you have the engine rebuilt? I just want to sure you aren't experiencing piston slap. In any case it SHOULD run smooth at full advance and a stock cylinder head even though it shouldn't be driven that way except at higher engine speeds.
 
Larry,

Could you expain your comment some ? Are you advancing the timing at idle ?

The spark advance should be used to set the timing as you drive. Different values of timing for different speeds/conditions.

Marc
 
Larry,I have everything rebuilt on my distributor also,and I still have a little back lash in the shaft. If I don't take care of it when I'm timing it I have the same problem. Also make sure the control rods are moving the distibutor back and forth in the range there supposed to.Good luck,Frank
 
Larry, It's funny you bring this up now. I recently noticed pinging at my 8:30 - 9 o'clock positions of my spark lever, where I usually drive at that setting all during the summer with no pinging at all. The engine is warmed up and all is fine. This seemed to happen overnight. My '31 pick up is all stock, rebuilt engine some time ago. I drive the Model A as much as I can, but I keep it out of the salt. I'm now wondering if it has to do with "Winter gas"? (87 octane, 10% crapahol).---Pete.
 
H. L. Chauvin said:
Larry,

Please verify exactly what you have done with Mr. Marco's Timing Instructions below, & then report back with your findings.

http://www.abarnyard.com/workshop/timing.htm
Click to expand...

H.L. Timing is on the mark, turning the crank when the timing pin goes in the dimple I get a spark at the points and #1 piston is TDC.


Tom Wesenberg said:
What's your compression ratio?
What's your compression while cranking?
Could you be using too hot of a heat range spark plugs?

My 28 with stock head and only 50 lbs. compression would also ping with very light acceleration, and I found it was due to a hot spot in the cylinder, which was caused by a buildup of rust flakes around the rear cylinder. After 30 days of the vinegar treatment I no longer have pinging.
Click to expand...

Tom, compression ratio? It is a stock engine with a stock head (original).
Compression shows 3 of the cylinders register 64 pounds, 1 registers 65 (give or take a pound). Running the original 3X plugs (new).


Patrick L. said:
Sounds normal to me.. I really can't see where these motors need 40º of ignition advance.. Every car seems to have its own 'sweet spot' which you need to find.. I never run full advance,, I run in the 8:30 to 9:00 position.. It'll run at full advance,, but,, it doesn't like it very much and even at that it doesn't ping/spark knock/detonate.. After awhile you will be able to 'feel' what it likes and dis-likes..
Click to expand...

Patrick L., 1crosscut --I agree but would like to have it run better even at 9 o'clock.

Marco Tahtaras said:
I've only seen that occur once. My buddy timed his car exactly as I taught him. However it turned out what he was sure was the dimple in the timing gear was not. He had it at least 15 degrees advanced. It was surprising he got as close as he did as the "false dimple" could have been anywhere!

Did you have the engine rebuilt? I just want to sure you aren't experiencing piston slap. In any case it SHOULD run smooth at full advance and a stock cylinder head even though it shouldn't be driven that way except at higher engine speeds.
Click to expand...

I went through the engine in early 60's. Don't recall what all I did to it but I do remember boring it out, new pistons and rings for sure. Put about 1500 miles on it, then put it away until late 80's. Like I told Tom 3 cylinders at 64 and 1 at 65.


Fred K-OR said:
Do you have your gas valve open to far? How far do you have it open or do you have it open at all?
Click to expand...

Fred - it's 1 turn out.

marc hildebrant said:
Larry,

Could you expain your comment some ? Are you advancing the timing at idle ?

The spark advance should be used to set the timing as you drive. Different values of timing for different speeds/conditions.

Marc
Click to expand...

Marc - yes, at idle

frank mcdaniels said:
Larry,I have everything rebuilt on my distributor also,and I still have a little back lash in the shaft. If I don't take care of it when I'm timing it I have the same problem. Also make sure the control rods are moving the distibutor back and forth in the range there supposed to.Good luck,Frank
Click to expand...

Frank - The travel is correct.

mass A man said:
Larry, It's funny you bring this up now. I recently noticed pinging at my 8:30 - 9 o'clock positions of my spark lever, where I usually drive at that setting all during the summer with no pinging at all. The engine is warmed up and all is fine. This seemed to happen overnight. My '31 pick up is all stock, rebuilt engine some time ago. I drive the Model A as much as I can, but I keep it out of the salt. I'm now wondering if it has to do with "Winter gas"? (87 octane, 10% crapahol).---Pete.
Click to expand...

Pete - Headed to town to get some "no ethanol" fuel and see if that will help things.

Thanks to all of you for your replies.
Larry
 
If it doesn't idle good with the spark fully advanced, clockwise backlash in the distributor shaft is effecting the timing or the timing is just wrong. Rebuilding the distributor doesn't remove backlash. Most that didn't grow up with model A's will have trouble setting the timing. The old guys taught me how to set the timing when I was in my early teens. If you are running the so called modern points, this will effect timing because the points are mounted in a different place on the upper plate. The timing instructions in most of the model A how to books are so confusing that most end up with bad timing and poor performance , if it runs at all. I first set my points, book says .018 to .022 . I set my points at .022 . All the talk about position of spark lever and when the points open causes confusion and should be ignored . Remove all of the spark plugs so that compression doesn't make it harder to find the timing dimple on the cam gear. When the timing pin drops in place set the trailing edge of the rotor tip poinhting at the number one contact in the distributor cap body , with no clockwise backlash. It may take several tries because when you tighten the screw that holds the points cam, the cam will try to move as well. If you can adjust the dist. cam so that the trailing edge of the roitor tip points at the number one contact in the cap with NO clockwise backlash, you will be at the so called sweet spot. There will be backlash in the shaft. As long as the backlash is adjusted out of the clockwise direction you should be good to go. Backlash in the counter clockwise direction has NO effect on the timing.
 
Larry,

a. Purdy is addressing an important point, i.e., distributor firing backlash.

b. Not only distributor shaft backlash; but, many often don't realize how many of the very best new "rotors" on the very best "distributor cams" have backlash; e.g., test by holding the distributor cam steady & try rotating the rotor back & forth.

c. Most "new" rotors have tight inside diameters on the bottom rotor opening that fits very tightly on distributor cams, & because it is tight it does not rotate easily, so it appears that the rotor's bottom plastic lug is in the slot; however, many "new" rotor lugs are narrower than the cam slot whereby when removing & replacing the rotor, it can be positioned in different locations, either farther CW or CCW which can affect timing.

c. Remembering that the distributor shaft & rotor turn counter-clockwise (CCW); hence when one has rotor play, it is best to turn the rotor clock-wise (CW) all the way on the distributor cam before or after installing to insure it will not rotate when the engine is running.

d. If one verifies TDC with No. 1 piston @ TDC when timing pin slips in, this will insure cam shaft timing & distributor "shaft" timing -- not yet distributor cam & rotor timing which will be adjusted later.

e. Even if one has lots of worn parts & distributor backlash occuring, after setting the timing, it is most wise to "again" fully retard the spark, "again" rotate engine CW until timing pin slips in, (knowing it is on TDC), then "re-check" to see if the points are just about to open when the rotor's metal tab is pointing to No. 1.

f. If one still gets engine pinging, & distributor timing is incorrect, possibly some former owner widened the slot in the rear side of the distributor body to further advance the timing.

Hope this helps.
 
Group,

I must be missing something. Why would the engine idle O.K. with full advance ? Surely the only reason for the ability to adjust the spark advance is so that the optimum setting is used at the different speeds ?

Isn't spark adjustment to take care of the inertia in the air/gas mixture and that the idle condition is very very different from highway speed , hence the need for adjustment ?

Marc
 
Why shouldn't an engine idle ok with full advance??? Mine all do! Mine idle pretty smooth with full advance and idles with a chick ah lunka sound with the spark fully retarded . The spark is needed for cranking and when creeping along on trails with sand beds and hills , to prevent lugging and timing knock. People that aproach hills at too low speed will need to slightly retard as the engine starts to lug.
 
H.L. is right on the money. If you do it like he said you will be in the right zip code. I've found the sweet spot at about 9:30 and agree that you need to fiddle with it if you are late on a hill and need to retard to climb it comfortable. New but learning and loving it !
 
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