351C M-Code engine Timing issue!

[Don C]

Changing the springs recurves the distributor, which is how soon the distributor will advance as the RPMs increase.

 

[Stanglover]

What springs should i get fir the distributor? Keep original!

I only have the 13L slot so i think i will weld and grind until i have 410”

I used one heavy factory (Ford) spring with slight freeplay and one Mr.Gasket 925D set tight.

 If you do it right, you'll need to remove the gear and pull the shaft out. Make sure you mark it first so it goes back on the same way. There is a chance the roll pin hole is off center. Good luck and I/we hope you get to where you need to be with it. It looks like you have engine mods to deal with as well, so this may also affect your results. Also, just thought of this, if there is ANY side play in the shaft bushing, I suggest having it repaired or replace the distributor. DON"T buy cheap Chinese junk!!

Cardone Select has a reasonable copy of the Motorcraft but the threads are metric instead of SAE. Cardone may have a remanufactured Motorcraft in stock, worth checking, but it will likely have a 15L slot at minimum.

Geoff.

Meyer,

The distributor does NOT necessarily even have to be removed from the engine to weld up the slot.

There should be a circular felt in the breaker cam mechanism, and under that there will be a circular clip that needs to be removed, (along with the advance springs) the brealer cam can then be wiggler off of the distributor shaft.

be sure to keep the orientation of the slot and what spring went where.

you will then want to put the weaker of the 2 stock springs were the stronger spring was, and the new weaker spring where the weaker oem spring was.

be sure to clean and lubricate well.

do Not try and take the weights off, (the plastic bushings WILL break, if you can possibly find replacement bushings, go for it.

Boilermaster

 Boilermaster and Meyer, my apologies, what was I smoking! You don't need to take the distributor out, the slot/cam plate can be removed as Boilermaster says. I happened to have mine out and in parts. Must be getting old or something!

I do not agree however on whether there is a particular side the heavy spring need to go UNLESS the weight are different, then it most certainly would matter. Setting the springs for tension is what's important for correct curve.

In the pictures, you can see that the weight are both G4, whatever that means. I measured the distance from the pins on the cam plate to the spring post on the base plate and they are both the same. All that matters is the slot width and resetting the rotor slot correctly to the engine, i.e. pointing toward #1 cylinder. In the picture, you will notice I was experimenting with a piece of nylon tube on the 13L slot, but although it was closer, it was not quite the equivalent to a 10L. Welding and re-cutting (round needle file) is best.

All this is based on what I found and learned. I was also in contact with a tech at Cardone who helped me with different weights and springs, but in the end it was my own experimentation that got my engine running the way it needs to be. As always, others have differing opinions and experiences, there's usually more than one way to skin a cat!!

Geoff.

 

[boilermaster]

Stanglover,

I too apologize, at the ford store when 351M/400 s were in their heyday (or not) nearly all of these engines had spark knock issues, we would take all of the slack out of the heavy spring post.

If one then swapped springs, you would immediately have a spark knock issue again.

Just force of old habits I guess.

When I was at the local pick and save salvage yard looking for useable cores, I found 3 candidates

(duraspark) they all had the heavy spring tang bent.

Boilermaster

 

[Meyer]

I did the 10L slot initial 12 no pinging anymore stock advance springs. Now on to a afr gauge to fine tune my 670 quickfuel

Thanks everyone

 

[boilermaster]

I did the 10L  slot initial 12 no pinging anymore stock advance springs. Now on to a afr gauge to fine tune my 670 quickfuel

Thanks everyone

Meyer, did you now re-do the idle mixture and idle speed ?

When me tuning me Holley, I am liking to see about 13.6-14.0 in high gear at cruise.

that's what the engine likes the most.

When the power valve opens (6.5 '') I tune the power valve restriction channel tp achieve around

12.6/1 afr.

I had to drill and tap my primary metering plate for this.

I am also using the quick fuel adjustable secondary diaphragm.

happy motoring

Boilermaster

 

[Stanglover]

Stanglover,

I too apologize, at the ford store when 351M/400 s were in their heyday (or not) nearly all of these engines had spark knock issues, we would take all of the slack out of the heavy spring post.

If one then swapped springs, you would immediately have a spark knock issue again.

Just force of old habits I guess.

When I was at the local pick and save salvage yard looking for useable cores, I found 3 candidates

(duraspark) they all had the heavy spring tang bent.

Boilermaster

 Thanks and I appreciate your knowledge and experience. Hopefully, this is not getting too involved for our new friend to understand.

 It seems like he (Meyer) is quite capable and achieving the goal of attaining the "no ping" zone!

 Just to conclude why I feel it doesn't really matter which side the springs are on provided the weights "X" and the base plate curve "<" are the same, then it follows that the light spring, which I did have to experiment with to find what worked best and finally chose the 925D, controls the first 2/3 rds of the curve and the heavy the last 1/3 rd or the high end rpm where a slower advance is desired. It really came down to adjusting the tension of each spring and finding that sweet spot. I think most would install the heavy spring "H" on the side facing the 10L slot whereas I have it opposite, hence the discussion. For me, that took several attempts and some frustration which I could have avoided by paying a friend to do it on his distributor machine, but I'm too cheap!!

 

[Stanglover]

T

I did the 10L  slot initial 12 no pinging anymore stock advance springs. Now on to a afr gauge to fine tune my 670 quickfuel

Thanks everyone

That's awesome!! You may now be able to bump you initial to 14-16 degrees, but try 14 first. Hopefully you have an adjustable timing light available to you?

I found 14* gave me really good idle speed, but I then went to 16* for a bit better response. That is for MY engine though.

Geoff.