Thought I'd pass on a lesson learned about points gaps. I was having a devil of a time tracing the cause of engine misfire > 1900 rpm with my Burtz engine set up with a stock head and Model B manifolds and carb. It turned out to be the points were set too wide and as they were incrementally narrowed, the engine ran to higher revs before misfire. I stopped the process when I was satisfied. It is close to the recommended .020" (which I looked up after my process) but may be a bit less.
Effect of too large point gap
- Thread starter JOHNCL
- Start date
Patrick L.
Well-known member
Dino's A
Senior Member
You also need to check for metal build up / metal transfer from the point arm to
the other post. I had an occasional small miss upon acceleration and had the
points with an uneven surface. I got out my trusty point file & dressed them until
a set of points I ordered came in. Metal transfer of the points is caused by either
an under capacity condenser or an over capacity one.
the other post. I had an occasional small miss upon acceleration and had the
points with an uneven surface. I got out my trusty point file & dressed them until
a set of points I ordered came in. Metal transfer of the points is caused by either
an under capacity condenser or an over capacity one.
CWPASADENA
Well-known member
Points set too wide will not allow enough dwell time for coil saturation and the output voltage will be too low to fire the plug under load, especially at higher engine speeds.
Chris W.
Chris W.
I report a lesson learned with a smile and get a reply chastising me with multiple exclamation marks. Al in NY you need to relax.
nkaminar
Well-known member
John, Thanks for the post. I also learned recently to set the gap between the rotor and the pins in the distributor housing as close as possible without interference. The specification is 0.025 inch although in my experience a closer gap will provide a hotter spark at the plugs.
Before I retired, I used to have a sign that I hung in my office that read "Don't let the bastards grind you down." Probably good advice for the forum too.
Before I retired, I used to have a sign that I hung in my office that read "Don't let the bastards grind you down." Probably good advice for the forum too.
ETAModel
Senior Member
Welcome to the Ford Barn.... you should've done a search of prior post on this subject before posting... LOL!
I had a similar issue as OP, engine would idle fine but rough at higher rpm. Turns out the points were close to 0.036". I closed them down to nominal 0.020" (actual gap will vary a bit due to variations in the distributor cam lobe height) and much mo' beddah.
BTW, when I'm doing this at home I set the points by removing the distributor and holding it in a bench vise. I then use a dial indicator on the outside of the point arm to measure how far the points open. For me and my mature eyesight, this is much more repeatable than using a feeler gauge in the car.
JayJay
BTW, when I'm doing this at home I set the points by removing the distributor and holding it in a bench vise. I then use a dial indicator on the outside of the point arm to measure how far the points open. For me and my mature eyesight, this is much more repeatable than using a feeler gauge in the car.
JayJay
rotorwrench
Well-known member
We all live and learn. I always figure an admitted mistake will not be repeated and admire the person a bit more for the admission. We've all been there. I know a lot more about ignition systems now than I did when I was younger and less educated.
Folks do have to develop a harder skin when posting on forums. Not everyone sees things the same way. I try to approach everything with certain amount civility so that I will get the same in return but I don't expect it in every case.
A lot of the new replacement breaker point sets are not made right and don't evenly match the oposite point as they should. I'm still using a set that I purchased back in the 80s since the last set I purchased were not usable without modifying the breaker plate.
Folks do have to develop a harder skin when posting on forums. Not everyone sees things the same way. I try to approach everything with certain amount civility so that I will get the same in return but I don't expect it in every case.
A lot of the new replacement breaker point sets are not made right and don't evenly match the oposite point as they should. I'm still using a set that I purchased back in the 80s since the last set I purchased were not usable without modifying the breaker plate.
Patrick L.
Well-known member
Yep, everyone screws up. Its all part of being human. So, why not admit, some folks don't like to. I guess thats all part of being human too. If I only screw up a half dozen times a day, its been a good day.
Experimentation isn't screwing up, I look at it as experimentation. We just have a need to see stuff for ourselves. Thats part of being human too.
And it is hard to respond to forums such as this. Things are usually typed differently than they would be said and its hard to see the facial expressions. [smiley face] ��
Experimentation isn't screwing up, I look at it as experimentation. We just have a need to see stuff for ourselves. Thats part of being human too.
And it is hard to respond to forums such as this. Things are usually typed differently than they would be said and its hard to see the facial expressions. [smiley face] ��
Tom Endy
Well-known member
I have always set the points at .020, then set the timing. A new set of points will start closing up as the rubbing block wears. As they close up the timing changes. Before 1000 miles the car will not run well and you will notice you have to keep moving the spark advance handle up. Resetting the points to .020 will restore the timing setting. Rubbing block wear will reduce as the block acquires a glaze. It is prudent to re-set the points to .020 every 1000 miles. Always set the point gap before setting the timing.
Tom Endy
Tom Endy
johnbuckley
Well-known member
"....Points set too wide will not allow enough dwell time for coil saturation..." I can believe that concept with engines that rev at 4000 or more , but it is really likely to be a factor on a stock A topping out at say 2600rpm?
Great idea! This will also tell you if there is any variation in cam lobe profiles.
I find that there is often up to 0.003"-0.004" variation high to low on the four lobes of a worn cam, down to 0.001"-0.002" on a new cam (some of that variation I'm sure comes from bushing/shaft wear). So I aim to set my points to not less than 0.018" minimum which leaves a 0.022" max. Any more than that, find a different cam.
Tom Endy's point about new points is a good one, although I've found that the degradation of a new rubbing block is much quicker - more like check it every 50-100 miles until it stabilizes.
JayJay
shew01
Well-known member
I feeler gauge is a pain for me too. This is what I use, and it seems pretty much idiot (me) proof. It’s a tad pricey though.
https://www.brattons.com/QUICK-SET-POINT-SETTING-TOOL/productinfo/17503/
Sent from my iPhone using Tapatalk
rotorwrench
Well-known member
I use the wire gauges for breakers & spark plugs. On funky cams, I've had to use a fine flat India stone and dress the high spots then polish to very smooth finish. Put some magneto cam grease on it and set it up for .020". The breaker block lasts a lot longer that way.
CWPASADENA
Well-known member
Remember, we are dealing with a 6 volt system and the original Model A coil did not have a very high secondary voltage output to begin with.
Chris W.
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