Snapping sound under load.
- Thread starter AzRay
- Start date
Tom Wesenberg
Well-known member
I don't know that spec off hand, but for a smooth running engine the most important spec is that the opening of the points be 90 degrees apart, so you have even firing between the cylinders.
Many, if not most, distributor cams have been replaced with the "B" cam, which gives a bit more dwell. Dwell is the time the points are closed so the coil can build up a strong magnetic field. I've measure the new cams and have found them to be within 1/2 degree, which is very accurate.
AzRay
Junior Member
Thanks Tom for the info on the Model A distributor cam. I'm going to order a B cam from Arizona Model A (by the way, great place to order parts). I'm unhappy that when I moved to Prescott two years ago I sold/gave away all my 'old car' tools. Dwell meter, compression gage and a few other items. I would have kept all that stuff if I know I would be wrenching on an 87 year old car today. The theory I spoke of this morning sort of went south after more thought. Still going to replace points, condenser and plugs (again). This will go with new distributor body, rotor, coil and wires. Did a couple of things last night and will test drive this afternoon. I don't want to change a bunch of stuff at once and then not know what fixed the problem.
pooch
Well-known member
It reminds me too of a thread on an MGB site a few years back.
5 pages of guesses why an engine would not start.
Even got as far as someone wanting the head removed.
Finally the dude checked the gas tank, it was empty.
Duhh.
Jacksonlll
Well-known member
Here is an old, 2010 video of our Amish Tour. Early in the video there is one car with an exhaust manifold leak. It demonstrates the sound of the leak, a tic-tic sound. Someone did have a new gasket and the repair was easy.
https://youtu.be/ZRq_Rb2Ojp0
https://youtu.be/ZRq_Rb2Ojp0
SeaSlugs
Well-known member
ya need to fix your running rich problem first... always fix the known issues before trying to fix the unknowns... alot of times that fixes mystery problems.
Mitch//pa
BANNED
Excellent advice ......it was mentioned in #17 also... after the recent posts it was worth repeating. swapping out parts never helps
SeaSlugs
Well-known member
yea ive heard snapping popping before on an A engine. Question: is it too rich of a mixture or too lean of a mixture that can get the manifold glowing cherry red?(aka enough heat to premature ignite fuel mix)
going up a hill the engine is under a heavy load thus means more heat generated...
Mitch//pa
BANNED
Attachments
tbirdtbird
BANNED
" is it too rich of a mixture or too lean of a mixture that can get the manifold glowing cherry red?"
ummmm timing too far advanced, not the mix
ummmm timing too far advanced, not the mix
Mitch//pa
BANNED
Dammit Mitch, quit using my car as a workbench!
QUOTE
But Vince It's not a fine point Model A with a bottle of soda::::
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tbirdtbird
BANNED
Yikes that's Charlie Howard's car
what is with the soda, Charlie
i was plate #7
what is with the soda, Charlie
i was plate #7
forever4
BANNED
Actually timing too far retarded, not advanced, will heat up the exhaust manifold red hot.
Dick Steinkamp
Well-known member
tbirdtbird
BANNED
generally agree on your take on timing, Dick, although the engine will overheat so quickly I am not sure the exhaust has time to get cherry red.
However, I worked on a 1911 Stafford car (last one left) 20 yrs ago that had its magneto ridiculously advanced (2 teeth on the timing chain as it turned out); it had been overhauled wrong which is why I was brought on scene. No one could get it started after the overhaul.
Well, that beast would dislocate your shoulder it would kickback so hard. But if you persisted you could actually get it started....but after 5 min the manifold was as cherry red as could be. There were no timing marks on the motor at all, so I had set up a degree wheel so I could time it by hand the old fashioned way. That was how I determined just how far advanced it was, and how many teeth to retard it. It was at 40° advanced with the lever in the full retard position!
never saw a manifold get so hot
However, I worked on a 1911 Stafford car (last one left) 20 yrs ago that had its magneto ridiculously advanced (2 teeth on the timing chain as it turned out); it had been overhauled wrong which is why I was brought on scene. No one could get it started after the overhaul.
Well, that beast would dislocate your shoulder it would kickback so hard. But if you persisted you could actually get it started....but after 5 min the manifold was as cherry red as could be. There were no timing marks on the motor at all, so I had set up a degree wheel so I could time it by hand the old fashioned way. That was how I determined just how far advanced it was, and how many teeth to retard it. It was at 40° advanced with the lever in the full retard position!
never saw a manifold get so hot
Dick Steinkamp
Well-known member
True dat, Dave. If the timing is advanced to the point of preignition (detonation) it will generate a lot of heat. I should have qualified my agreement .
SeaSlugs
Well-known member
i did look into a model A recently where the point gap was on the verge to too large. Once it started it ran rough, coughed clacked backfired as it was just enough gap to fire on 2 maybe 3 cyl but not consistently due to slight variances in distributor cam lobes and possible slop. Timing was dead on. Reset point gap to .020 and fired up quick and purred like a kitty.