Timing question

[bstandley1]

After installing new wires, rotor, cap, and a Pertronix Ignitor, I proceeded to set the timing. I disconnected the vacuum advance , plugged the hose, then started the car. The initial timing at idle was approximately 14 Degrees BTDC. I revved it up to approximately 4500 RPM, but the timing only advanced 10 to 12 degrees (24 - 26 degrees total timing.( If memory serves, the centrifical advance is supposed to add about 20 Degrees of timing???) My trusty instructions from Southern Automotive call for 32 - 34 degrees of total timing. Any suggestions on what I should do next? Appreciate any input...

Bob

[Jim Harding]

Bob,

You didn't mention it, but I'm assuming that the centrifical advanced gave you the desired 32 to 34 degrees prior to your tune up..... so it must be something that you had a hand in with your tune up, or something else happened to restrict the advance weights from doing their job.

Pop the cap off the dizzy and move the rotor manually through out it's mechanical advance. See if you can feel some binding or perhaps some more mussel is needed to get it to move out. This is a judgement call and requires some calibrated fingers, but you can probably get an idea if it feels too tight. If you had to remove the breaker plate to fit the Pertronix ignitor, maybe one of the screws is now poking too far below the plate and causing it to bind against the weights. Or go the extra step and remove the breaker plate and have a look see at the springs and weights to see if something looks suspect.
By the way, what kind of dizzy are you using? Does it have adjustable mechanical advance?

- Jim -

Jim Harding
La Plata, Maryland

1982 #3004
http://www.capitalareacobraclub.com/albums/album26/1aLeftside.thumb.jpg

[bstandley1]

Jim,
Thanks for the tips... the total advance was around 26 degrees BTDC before I installed the Pertronix. I didn't bother to check the initial timing then so I'm assuming that the timing issue is independent of the Pertronix install. I have an old Motorcraft single point distributor in my car. I think I'm going to pull out the breaker plate and see if I can find anything obvious.

Bob

[Poorboy]

Sounds like you have the same amount as before you did any work, but without the vacuum hose hooked up. Total advance would be with the vacuum hose hooked up.

[Jim Harding]

Bob,

I also have a Ford single point dizzy with single stage vacuum, and just checked my advance to see what I have....

Initial advance is set to 12 degrees.

Rev it up and total advance reads around 34 degrees, all in by 3000 rpm

Connect vacuum and slowly raise rpm and max advance is around 41-43 (or so) degrees at 17 inches of vac.

According to notes I've kept, I've had it as high as 48 degrees before pinging was really noticable at part throttle.

My engine is a 30 over 302 with a mild cam, 9.5 comp, ported iron heads and a 4 bbl carb. Engine makes around 300 HP... not excessive and very streetable and not to bad on gas mileage either, around 17 on the road when I'm not acting stupid;)

Jim Harding
La Plata, Maryland

1982 #3004
http://www.capitalareacobraclub.com/albums/album26/1aLeftside.thumb.jpg

[Aggressor]

Bob
The following link may help. It is an article on Ford distributors and timing.

www.fordmuscle.com/archives/2000/03/timing/index.shtml

Note the one image that shows the centrifugal advance rotor arm with timing index limiting slots. The difference in centrifugal movement could be a minimum of 10 degrees (20 degrees at the crank) to as high as 18 degrees (36 degrees at the crank). My distributor came with a centrifugal rotor indexed at 10 degrees on 1 side and 13 degrees on the other. It originally was set to 10 degrees. I removed the rotor and replaced it on the 13-degree side to give 26 degrees mechanical advance. I then replaced the advance springs with lighter units from a recurve kit that I got from Summit. With 11 degrees initial timing I get 37 degrees full in at 2600 RPM.
Your problem seems to point to the centrifugal advance being possibly restricted in some fashion. Even with the 10-degree minimum slot in the advance, you should get a 20 crank degree advance. Jim could be right about a breaker plate screw extending too deep and causing a restriction or binding. Another possibility could be that an advance spring is loose or missing and your idle timing of 14 degrees reflects some of your centrifugal advance already dialed-in.
Plug your vacuum line and don’t worry about vacuum until you get your initial and centrifugal corrected. Then add the timed port side vacuum. The vacuum advance is a value-added "bonus". Under light load conditions, there is no reason not to take advantage of the extra advance. Under hard acceleration, your vacuum drops sharply and the vacuum advance is a non-participant. My FE seems to like this setup. It is an extraordinary performer that also cruises rather smoothly and can get up to 20 miles per gallon on the interstate with the extra advance.

-Geary

[bstandley1]

Geary and Jim,

Thanks for the help. I pulled the breaker plate out, cleaned it up and put some grease on the pivot points; it doesn't seem to be binding at all.

Next, I took a look at the centrifigal advance set up. There were two advance tabs; one marked "13L" and the other "15L". I compared the two springs on the tabs ... one is very lightly sprung (can move the tab easily) and the other is much heavier and it is difficult to move at all. I'm guessing the reason I'm getting so little advance is because of the tension on the heavier spring. I'll head to the NAPA store tomorrow and see if I can find an assortment of advance springs and start experimenting. Thanks again for the help and I'll let you know how it all turns out.

By the way, is 28 Degrees of centrifigal advance in the ballpark for a moderately built 351W?

Bob

[Aggressor]

Bob, If your advance tabs are 13L and 15L your choices are 26 degrees and 30 degrees respectively for centifugal. If Bill Parham suggests 32 to 34 degrees total timing use the 13L for 26 degrees mechanical. and make up the difference with the initial setting. The light/heavy spring combination allows part of the advance to start early on the light spring to support off-idle accelation and the heavy spring controls the curve at higher rpm. Call Bill to get his input.

-Geary

[bstandley1]

Thanks Geary,

I'm a little slow on the uptake<img src=images/icon_speech_duh.gif border=0 width=23 height=15 alt=Insert Speech Icon: Duh!> I took a closer look at the distributor and confirmed that the "13L" tab was in play. I'll give Bill a call and see what he recommends regarding spring tension. Thanks again ...BTW I noticed that you live in Harrisburg... I use to live across the Susquehanna in Mechanicsburg ... small world!

Bob

[bstandley1]

Just a quick update ... called Bill Parham yesterday and he provided me some background on my motor. Bill told me that I have a 9.9 compression ratio and should be burning 93 Octane gas.... may have to shop around for some attitives since the highest octane available at the pump here is 91. One of his mechanics told me to experiment with different tension springs on the 13L advance set up until I achieved full advance (33-34 degrees) around 3200RPM. I ordered a Mr Gasket spring set that's supposed to arrive on Friday.The adventure continues...

Bob

[pgermond]

91 octane is max in CA also..... I'm on my second drum of Sunoco Purple (110). Mix it 70-30 to achieve 100. That may change w/the recent jump in the cost of petrol :(

Phil

427 Roadster, #4279436
Southern Automotive FE
3:31 and Toploader

Roseville (N.Cal)

[bstandley1]

Quick update:

Picked up a replacement spring at the local Ace Hardware with about half the tension of the old one, (I"ll keep the Mr Gasket set as a momento :)), set the timing to a total advance of 34 Degrees BTDC. The advance worked smoothly with full advance around 3100 RPM. Took it for a spin and what an improvement!!! Think I found the missing horsepower. Only thing I've noticed is an extremely slight miss under light acceleration; it clears up with a little throttle (vacuum advance?). Thanks to all for your valuable help.

Bob