Model b distributor advance curve
- Thread starter RUNNERBUN
- Start date
Vince's site has some information on the curve.
http://www.fordgarage.com/pages/bdistributoradvance.htm
Bob
http://www.fordgarage.com/pages/bdistributoradvance.htm
Bob
RUNNERBUN
Well-known member
Thanks Bob, I have seen his site and have learnt quite a bit from it. Unfortunately his discussion and information relates only to the maximun theoretical advance possible with a B distributor. The info I would like to get my hands on is what degree of advance at any given RPM. should the B distributor have.
Unfortunately information on the 4 Cyl B Ford is very hard to locate and appears lost somewhere between the Model A and the V8's
Thanks again,
Runnerbun
Unfortunately information on the 4 Cyl B Ford is very hard to locate and appears lost somewhere between the Model A and the V8's
Thanks again,
Runnerbun
Walt Dupont--Me.
Well-known member
I believe the B dist only has 8 degrees machanical. The static timing is 19 degrees. I don't know at what rpm the 8 degrees start. When you put the timing pin in the B front cover and it goes into the detent on the cam gear, that is 19* btc. The hole in the cover is in a differant location than an A front cover. I've seen A engines with B covers and vice versa, the timimg is never right when that happens. The A engine times on TDC and the hand lever under the steering wheel advances to 28* I like the A dist better than the B dist. Walt
RUNNERBUN
Well-known member
No Bob,I don't have a copy of the service bullitins, any ideas where I may get a copy of the graph?
Walt, thanks for that I must admit that I did get caught when I replaced my A motor with the B motor a couple of years back. It drove me stir crazy getting the timing right and nearly came to the point of taking the motor out of the car when I realised that the timing cover and pin location was different.
Walt, thanks for that I must admit that I did get caught when I replaced my A motor with the B motor a couple of years back. It drove me stir crazy getting the timing right and nearly came to the point of taking the motor out of the car when I realised that the timing cover and pin location was different.
B_man_Al
Senior Member
Something I found very useful was to make a calibrated right angle bracket, attached to the motor mount bar with 5 notches corresponding to 0,10,20,30 & 40 degrees. I then set the engine to TDC and filed a small nick in the crank pulley corresponding to 0 degrees.
Using this, you can use a timing light and see all that advance stuff going on. I actually found my advance weights were not working properly using this.
Its not super accurate because it is not curved, but its way better than the recommended way with the pin and turning the rotor to just open on #1.
Attached is a photo.
Using this, you can use a timing light and see all that advance stuff going on. I actually found my advance weights were not working properly using this.
Its not super accurate because it is not curved, but its way better than the recommended way with the pin and turning the rotor to just open on #1.
Attached is a photo.
Bruce Lancaster
Member Emeritus
Best is to find out via timing light what your own distribuitor is doing...after 80 years the springs and pivots may have a few quirks.
Vince makes it pretty clear that as sold the curve is way too slow...I haven't actually worked on this but have dug a little bit.
Lighter springs would be quickest way to attack this...I dug through a mailorder speed catalog and ordered a bunch of recurve kits from various muscle car era distributors, as distributors with mechanical advances are practically extinct in the junkyards around here.
GM/MSD stuff no good...all made for bigger and heavier weights than B.
Ford and Mopar kits have springs approximating B size and seemingly a bit lighter. Time to experiment, using a marked pulley and timing light but have not yet.
Remember:
You can use same or different springs in the two places
You can bend one to have a longer loop at one end so it does not resist until timing has moved some...this is to get more of the advance early in curve
Any advance happening beyond your driving RPM range is wasted
More weight in the weights is another possible tinker...a common trick is to drill holes and refill tehm with lead
At any rate, this sort of messing around is pretty cheap and a good way to learn what yor engine likes
Vince makes it pretty clear that as sold the curve is way too slow...I haven't actually worked on this but have dug a little bit.
Lighter springs would be quickest way to attack this...I dug through a mailorder speed catalog and ordered a bunch of recurve kits from various muscle car era distributors, as distributors with mechanical advances are practically extinct in the junkyards around here.
GM/MSD stuff no good...all made for bigger and heavier weights than B.
Ford and Mopar kits have springs approximating B size and seemingly a bit lighter. Time to experiment, using a marked pulley and timing light but have not yet.
Remember:
You can use same or different springs in the two places
You can bend one to have a longer loop at one end so it does not resist until timing has moved some...this is to get more of the advance early in curve
Any advance happening beyond your driving RPM range is wasted
More weight in the weights is another possible tinker...a common trick is to drill holes and refill tehm with lead
At any rate, this sort of messing around is pretty cheap and a good way to learn what yor engine likes
RUNNERBUN
Well-known member
Thank you all for your input. Bob that graph is just what I was looking for.
Bruce you are very correct. After 80 odd years who knows how or if the distributor has been tampered with and what the condition of the springs may be and what the distributor may actually be doing. That is why I was chasing the graph.
I have two original B distributors both of which were showing considerable wear at the shaft where the points cam pivots resulting in the points gap all over the place and a very eratic advance rate.
I have now rebuilt one of the distributors by turning down ththe worn shaft and resleeving with stainless steel, resulting in a consistant points gap and a smooth advance curve.
"B manAL" I have also fitted a timing bracket similar to yours and this has been accurately marked for both TDC and the standard B setting of 19 BTDC off the Cam gear/Timing cover/pin.
Now for the million dollar question!!! If the standard timing setting is 19 BTDC (I'm sure we all agree it is) why does the graph show that the timing curve start at 15 BTDC. Am I missing someting here???
Bruce you are very correct. After 80 odd years who knows how or if the distributor has been tampered with and what the condition of the springs may be and what the distributor may actually be doing. That is why I was chasing the graph.
I have two original B distributors both of which were showing considerable wear at the shaft where the points cam pivots resulting in the points gap all over the place and a very eratic advance rate.
I have now rebuilt one of the distributors by turning down ththe worn shaft and resleeving with stainless steel, resulting in a consistant points gap and a smooth advance curve.
"B manAL" I have also fitted a timing bracket similar to yours and this has been accurately marked for both TDC and the standard B setting of 19 BTDC off the Cam gear/Timing cover/pin.
Now for the million dollar question!!! If the standard timing setting is 19 BTDC (I'm sure we all agree it is) why does the graph show that the timing curve start at 15 BTDC. Am I missing someting here???
You aren't missing anything here. Over the years many folks have pointed out what is regarded as an error in Ford's own document. The graph shows the correct advance of 13 degrees, but they mistakenly start with an initial 15 degrees.
My testing of several new and out of the box NOS Model-B advance mechanisms shows an advance of 12-13 degrees as measured on the edge of the distributor casting. This combined with the initial 19 degrees gives a total advance of 31-32 degrees, which is sufficient for the stock 4.6:1 compression. I noticed some variation in the shape of the curve when testing on a running engine as some will max out at around 2600 RPM and others need 2900 RPM to hit maximum advance. The stock advance curve also works well with a higher compression head - I have a 5.5:1 Snyder head.
My testing of several new and out of the box NOS Model-B advance mechanisms shows an advance of 12-13 degrees as measured on the edge of the distributor casting. This combined with the initial 19 degrees gives a total advance of 31-32 degrees, which is sufficient for the stock 4.6:1 compression. I noticed some variation in the shape of the curve when testing on a running engine as some will max out at around 2600 RPM and others need 2900 RPM to hit maximum advance. The stock advance curve also works well with a higher compression head - I have a 5.5:1 Snyder head.
RUNNERBUN
Well-known member
Many thanks URSUS, I was hoping that was the case. I did quite a bit of testing today and I'm very happy with the result.
With my timing set at 19 btdc with a timing light and a little adjustment on the springs I'm achieving an advance of 12-13 degrees giving me a total of 31-32 @ 2400rpm. At 2400rpm with a high ratio differential that gives me a high end speed of 55 mph, and I don't think that I would be interested in any more speed than that. She runs very sweetly at 50-55 mph.
Thanks again to all who contributed. Seasons greetings to all.
Runnerbun
With my timing set at 19 btdc with a timing light and a little adjustment on the springs I'm achieving an advance of 12-13 degrees giving me a total of 31-32 @ 2400rpm. At 2400rpm with a high ratio differential that gives me a high end speed of 55 mph, and I don't think that I would be interested in any more speed than that. She runs very sweetly at 50-55 mph.
Thanks again to all who contributed. Seasons greetings to all.
Runnerbun
Two more thoughts: 1) don't forget that you can tweak the timing while the engine is running by loosening the screw on the upper plarte and moving the plate to advance or retard the timing (I believe each gradation on the scale = 2 degrees), and 2) be careful when altering the spring tension or weights as it is very easy to mess this up. The Ford instructions that come with a replacement shaft and advance mechanism have a very explicit caution about altering anything as each one is assembled and tested to spec as a unit.