Just changed rear ends(again) finally got a 9".  I have some highway gears in for the present time, which has prompted me to start tinkering with the carb again, which has refreshed my memory about the timing.

Last I checked it Liked about 17 to 18 deg. base timing.  This would nuke it if I ran it as it would be somewhere around 45 deg. total. 

I read up & found several articles about limiting the total mechanical advance & want to modify my distributor. I already have the allen head adjustable vac pod. 

What have you guys been doing with you factory dist. to get the timing curve & base time to perform?

I have seen "re-curve Kits" before.  Anyone used one on our engine?

I have a .060 over 292, E-4 straight up w/silent chain, 57 intake, 600 Edelbrock, pcv to carb, c1te heads ported & pollished w/1.78 intakes, & 1.6:1 roller rockers, headers & duals.

I still only pull 13" vac @ Idle.  Not sure if that's normal for a setup like this on a Y.

I have about 12 deg base timing, & total of about 38.  I only let the vac. can put in about 3 of that in an effort to keep the base as high as possible.

Thanks Fellas.

It sounds like your motor likes the 17°-18° initial static timing? Hope thats correct. If you want to use that setting, and limit the maximum to 38° - you will need an upper rotor shaft with a "10L" slot. This photo shows one off my bench with 13L and 18L slots.

The stop in the advance mechanism is .22/.23 wide in the sample I checked - this is with the plastic sleeve still over it. Subtraction and dividing and whatever  - says a slot for 10° would be about .44 or so. And an 8° would be near .39 (might have to make one).

If you can come up with a 10° slot (20° at the crank) you can use the desired 17°-18° initial and get total mechanical down to 37°-38°. then you have to choose springs to get the rate. This has always been trial and error for me - but if you can get help from someone with a distributor machine, it will go quickly. Maybe start at trying to get it all in by 2800 and go down from there. There is a Mr. Gasket spring kit for Fords #925D(?) or something close to that. 

The total advance - with the vacuum pot connected - can go pretty big with "no load" - 50+ is common.

Are you running manifold vacuum on the advance pot at idle? Usually that helps raise the idle vacuum level.

 
 Steve Metzger       Tucson, Arizona

Thanks for the info Steve.  It looks like a kit & some junk yard searching may be in store for me.

I did want to comment on the connection of the advance that you suggested...

I have always found ported vaccum to be best, especially on a street motor.  The whole point of vac. advance as I understand it is to assist with milage, under load. 

 If I were connect to manifold vac, under load it will actually act as a sort of retard.  (no punn intended!!) For example,  if I go from cruise part throttle, to a slight incline & slight to moderate increase in throttle application which is essentially more load; manifold vac would go from applying advance, to un-applying advance, thus the reverse of what it was intended to do. 

Ported is based off of venturi velocity, thus when you crack the throttle under load you get a boost of ignition timing to help burn the additional fuel that the carb meters under low vac, increased load.

Anyone?    Feel free to correct me if I'm goofed up on this.

I know this can get touchy,  but I say just the opposite. The vacuum advance is for cruise only to increase milage, when you go to full throttle you want the extra advance to go away to prevent detonation. When I know I'm going to carry a load I disconnect the vacuum advance so the engine wont "ping" because it is working harder at partial thottle but still has vacuum to the advance.

   Ported vacuum is from a port just above the throttle plate, it will give you manifold vacuum when the throttle is applied but not when it is closed at idle.

   God Bless.   Tim                           http://yblockguy.com/

350ci Y-Block FED "Elwood", 301ci Y-Block Unibody LSR "Jake", 312ci Y-Block '58 F-100, 338ci Y-Block powered Model A Tudor

tim@yblockguy.com  Visalia, California    Just west of the Sequoias

None of the new style carbs have the venturi vacuum feature (as far as I can tell) - just the "on/off" with the throttle blade as Tim said. Ted has mentioned modifying a modern carb to supply venturi vacuum before - but I don't know how you would go about it.

If you run the modern style "ported" vacuum -  at idle, the sucker will run at the initial timing setting. Then it "turns on" the manifold vacuum as you accelerate the engine with the throttle blade open. At that point everything works just like when you use straight manifold vacuum. Put a gauge on both ports at the same time and check its function - pretty easy to see.

I like running the engine with manifold vacuum at idle - runs cooler during the "burn down test". Running it in the "retarded mode" (initial advance only) no vacuum - will produce a nice sound and a lot of hot water. 

 
 Steve Metzger       Tucson, Arizona

When you say the cam is installed straight up, did you infer that the camshaft is degreed in and installed at 108° intake lobe centerline or simply installed in the zero position on a multi-slotted crankshaft gear?  I like 4° advance with the E4 camshaft or installed at 104° intake lobe centerline.  Simply installing the gears so that they are twelve pins apart is not the same as degreeing in the camshaft.  I ask because this makes a difference when trying to troubleshoot.  What’s the cranking compression look like?

This is a mod that’s only performed on a ’57 and later style of carb when attempting to run the early (pre ’57) Load-O-Matic distributors.  And the only distributor worth doing this for is the ’55-’56 T-Bird units when a ’57 T-Bird distributor is unattainable and still wanting to run a modern style of carb.  Much of this modification is trial and error as each engine combination ultimately has different requirements and the modification itself varies depending if being performed on a Ford, Holley, Demon, or Carter (Edelbrock) carburetor.  Likewise, I’ve modified the Holley 4000 4 bbls (Teapots) so they could be used with the ’57 and up distributors.  This is a much easier mod as it simply requires the blocking off of the venturi vacuum which tees into the ported vacuum circuit.  But life can be made simple by lieu of simply using ’57 and up distributors with ’57 and up carbs.  Some adjustments may need to be made to get the curve right, but the basics are there without having to re-engineer the whole shooting match.

But in regards to the use of ported vacuum for the distributor, I have found it necessary to relocate the ported vacuum holes in some of the Demon carbs as the hole has been too high above the blades and was providing insufficient vacuum for the distributor.  This ends up limiting the amount of ignition advance available in cruise situations.  Lowering the hole and/or resizing it larger increases the amount of vaccum to the distributor and thereby allows for additional cruise ignition advance.

 

Gas mileage is the fuel economy as stated in miles per gallon or mpg.  This value can vary depending upon how the vehicle is driven, whether it's town or highway driving, and the fuel quality among other factors.  Improved fuel economy is the recipient of a correctly working advance chamber which is why so much effort goes into getting it right but the ported vacuum part of the signal allows the engine to idle and take off without the surging or quirkiness associated with running the distributor vacuum directly off of the intake or a vacuum port located under the carburetors throttle blades.  A properly tuned vacuum advance will net an additional 3-4 mpg while maintaining a basic tuneup that will not clatter or detonate under heavy loads.  It’s not unusual to go even leaner on primary fuel jetting when the vacuum advance portion of the system is up to speed.  This is a subject that could be devoted to a whole book in itself so it’s difficult to expound on it in any detail in a paragraph or two.

 

As always, this is fuel for thought so feel free to pick it apart.

 

Lorena, Texas (South of Waco)

If you are you are running a later carb with the '55 "Load-O-matic" distributor and have the vacuum diaphragm hooked to ported vacuum nothing is working right. There is no mech. advance in those distributors and the vacuum is supposed to be hooked to venturi vacuum so it comes on gradually as you increase the throttle. What you will get is initial timing at idle, then when you crack the throttle full advance, and loose it as you push the peddle farther. "57 or later dizzy is needed.

   God Bless.   Tim                           http://yblockguy.com/

350ci Y-Block FED "Elwood", 301ci Y-Block Unibody LSR "Jake", 312ci Y-Block '58 F-100, 338ci Y-Block powered Model A Tudor

tim@yblockguy.com  Visalia, California    Just west of the Sequoias

Yes you need a 57-up distributor.Go to Napa or one of the parts stores and ask for a distributor for a 64 F100 with 292(last year used).Price is $40.00 -$80.00 depending where you buy so check around.You will also need cap and rotor for 57-74 Ford V-8.Wires should be reusable unless you want to install a new set.Run your vacuum line to manifold source unless there is a provision for it on your carb.You will be very happy with the improved driveability of the later distributor.Ford went to the dual advance distributor when they changed intake design and introduced the standard pattern Holley 4bbl in 1957.Hope this helps.I cahanged my 56 over to this setup this summer and it works great.

  

When you do this changeover let us know how it works out.You can start your own  topic on this by clicking on "add topic" at top left of page.Regards,Mark

  

What exact carburetor are you running?  You didn’t specify if it’s a three bolt or a four bolt.  A three bolt flange at the carb uses the original Load-O-Matic distributor while a four bolt 2bbl carb will require the later model distributor.  And is the vacuum advance chamber on your current distributor working?  You may need to do a vacuum check on the vacuum pot or check with a timing light to verify that the vacuum pod is indeed functioning.  And like everyone else is mentioning, if you do have a ’57 and up carb/intake combination, then you do need to upgrade to the ’57 and up distributor.  But....if you still have a three bolt carb, then the vacuum advance chamber at the distributor or the line feeding it is suspect and needs to be looked at.

Lorena, Texas (South of Waco)