Flathead spark curves.........

[BUBBAS IGNITION]

The last post " crabb-ie patties" was a buildup on the two bolt Ford Crab distributors.
Ole Ron , Bruce and a couple others requested some spark curve buildups. So here goes , i have a couple customers units for next week and will map up some spark curves before and after.
Any particular numbers you wish to see just post here and i will get them done sometime next week. I can also do a couple on the 49-53 Distributor as well if needed. ( Using our chevrolet conversion).
Theres some discussion regarding the vacuum brake and engine vacuum etc .
So jump in and lets get er done.
I will start with a customers old greasy unit right off the car and do some testing before any clean up. ( might even slip down to the shop tomorrow)

 

[jdl]

Looking foward to your info.. Thanks for doing this for us.

 

[Lawrie]

What about a 33-34 dist,curve.Thanks Lawrie

 

[BUBBAS IGNITION]

What about a 33-34 dist,curve.Thanks Lawrie

I will add one in as well.......

 

[BUBBAS IGNITION]

Had a minute and stopped by the shop , ran this crab right out of the box....
Good start and pretty average unit i would think ??
A couple interesting facts.
1-the vacuum piston is froze and the leather stop is cut almost into the metal , allowing NO drag to the piston.
2-Points are pretty burnt , however ran ok on machine at 40 degrees of dwell ( bit high)
3-Center picture shows misfire at 6000 rpm !!!!! Ran well up to that.
4-Spark advance ( mechanical is 12/24 degrees at 1400 rpm)
5-Advance floats 2-4 degrees at idle bouncing around

Heading to the cleaning tank for some work.......

 

[BUBBAS IGNITION]

Got er cleaned up and taken apart today , ran some tests etc...Heres the pics from the shop will add verbage tonight....
Excuse the 1952 Jag distributor picture, another story ..................
Basic build , clean and polish etc. Answered question about plug in stead of screw in bottom of wick. Drilled hole and popped out . Lubed wick and reinstalled plug filled drilled hole with dab of silicone. Installed CS47 contacts and adjusted on machine , ran at 3000 plus for 4-5 minutes and rechecked dwell per point....

 

[BUBBAS IGNITION]

Ran curve with NO piston and then added and adjusted piston....

 

[BUBBAS IGNITION]

Some data to digest :

1= First curve was without vacuum piston installed, advance was bouncy and jusped around a bit. Believe unit needs the piston load to stabilize the advance. 22 degrees at 2200 rpm
2=Installed clean /lubed piston.....Advance curve moved up the scale a bit and remained steady. 22 degrees at 3000 rpm with load on piston.
3=With vacuum adjustment all the way out , 7 complete turns will retard timing 12 degrees engine timing.
4=It takes 10 inchs of vacuum to began moving piston with light tension adjustment. ( light is just having contact with advance) Maybe a couple turns inward....

Interesting observation if spark advance is in at cruise speed at 2500 rpm and 20 degrees, AND vacuum drops to between 4-7 inches of vac the unit retards 20 degrees !!!! Almost a perfect overlap of advance going both directions.

Now the discussion would be what is the actual carb fitting vacuum at different rpms.
What happens to this vacuum when multiple carbs are used ?
How much lower is this vacuum when a high lift camshaft is used.?

Can someone hook up a vacuum gauge to a single carb flathead and drive the car ?

Is the intake vacuum different from carb fitting vacuum ????????

The only thing i can conclude at this point is the fact that these distributors ( cleaned and serviced) are 22 degree mechanical advance units. AND the fact that that they do need the piston and leather stop for proper operation.

Ask away ?????????

 

[BillM]

3=With vacuum adjustment all the way out , 7 complete turns will retard timing 12 degrees engine timing.

Does this mean with vacuum adjustment screw initially backed all the way out (counterclockwise) and then turned in (tightened) 7 turns?

 

[BUBBAS IGNITION]

Does this mean with vacuum adjustment screw initially backed all the way out (counterclockwise) and then turned in (tightened) 7 turns?

Yes , i used this to show the actual effects of adjusting the piston. Ford says to loosen and then test drive turning screw until slight spark knock/ping is gone.

 

[F1 MIKE]

Yes , i used this to show the actual effects of adjusting the piston. Ford says to loosen and then test drive turning screw until slight spark knock/ping is gone.

Bubba how about the actual effects of manual timing tab up and down of total advance can you show it thanks.

 

[BUBBAS IGNITION]

Bubba how about the actual effects of manual timing tab up and down of total advance can you show it thanks.

With just the screw installed, the stock travel from side to side is 10 distributor or 20 degrees engine timing.
Moving one mark on the marker is 4 degrees engine.

And ( just a rumor) i have heard of guys milling out the slot just for hill climbing for more intial timing kinda like the picture???
I would think thats cheatin , isnt it....??

 

[Kahuna]

Bubba
Do yopu know what the maximum advance (total) is for a flathead? I understand that different combustion chambers would make a difference, but most heads are pretty "standard", I would think. Is 26-28 total too much?
Thanks
Jim

 

[Ol' Ron]

Thanks Jim, this is definitely good information and proves a point that the Ford engineers had it right. Can't believe they went to the Load a matic..
I try to tell people not to remove the piston, but sometimes this falls on deaf ears. The vacuum in the intake doesn't change regardless how many or whit kind of carbs your running.
However the cam will, a typical L-1oo will idle at about 14"

Now lets see if I get this right. Distributor max advance is 22 degrees? Inital around 4 degrees = 26 degrees total. I like this for a 276 with 8.5CR and an L-100. In cruise.
Now , you say that WOT will drop total advance 12 degrees? This brings total timing down to 14 degrees? A little low for max power.
In my group of friends there are 2 guys running this system right down to the L-100 cam and they run great.
One of these cars has an MSD computerized ignition timimg system and this doesn't work at all. However it may be broken.
Keep up the good work.
Ol' Ron

 

[BUBBAS IGNITION]

Bubba
Do yopu know what the maximum advance (total) is for a flathead? I understand that different combustion chambers would make a difference, but most heads are pretty "standard", I would think. Is 26-28 total too much?
Thanks
Jim

Our engine on the dyno wanted 28 degrees. Any more or less we lost horse power.
I am sure different combos might want more or less but i have used the 28 for soem time.

 

[38 coupe]

Interesting. The Ford Service Bulletins say all 32-48 V8 distributors except the 40A have 18 degrees mechanical advance and the 40A has 22 degrees.

 

[Bassman/NZ]

This is great stuff. The ignition is a well overlooked part of a great running flathead. Jim, you'll receive my distributor shortly for a good going over.

 

[Tom's36coupe]

A big thanks to Jim for fixing my Mallory unit on my 36 coupe, it has never run so well! I am going to send my distributor from my 60 T-bird and 70 trans am Firebird next for Bubbas magic!

 

[Lyle]

Man I was just asking about that. I did not look before I spoke.

 

[Ol' Ron]

Jim that's very interesting 28 degrees for max power. All our tests give max power at 17-20. in fact, using a computer retard at hi RPm produces more power. Enter the twilight Zone of the Flathead.