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Correct distributor position at TDC?

February 3 2008 at 10:48 AM

RDave  (Login FairlaneCobra69)
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I am getting ready to do a first start on a new engine. It is a NOS 428 Service block with a new Lunati 10503 (428CJ replica) cam and a NOS Autolite distributor. So all new or NOS components were used.

According to Steve Christ's book "How to rebuild your Big Block Ford" on page 142 he says to rotate the crank to TDC for #1 piston, and insert the distributor. He goes on to say "With the distributor installed, you should be able to rotate the housing about 25 degrees clockwise and 15 degrees counterclockwise. This will ensure enough room to rotate the distributor to set ignition timing. Set the timing as soon as you can after you start the engine. Turn the distributor clockwise to advance timing and countercloskwise to retard it".

Here is a photo of my engine with the distributor installed exactly as Steve Christ recommended, with the caran at TDC and the rotor pointing at the #1 spark plug spot. I am using the vacuum advance as a point of reference in all of the photos. I was able to advance it 25 degrees clockwise, and 15 degrees counterclockwise with the distributor in this position:

[img][/img]

My question is, how come you see so many FE engines installed with the distributor in the position as it is in the photos below? Granted this distibutor has the advance timing set and mine does not, but it seems that these distributors seem overadvanced to begin with, and they would have had to advance the distributor almost the full 25 degrees clockwise to get to that position. Could the distributor gear be advanced 1 tooth too far on the on the cam gear? Or is this just normal wear of the components?

[img][/img]

[img][/img]

Also I thought I read a post here a few years ago about a method of setting the initial timing with a timing light without starting the engine, just by hooking up the timing light, setting the crank to 10 degrees BTDC, turning the ignition key to on, then just advancing the distributor clockwise until the timing light went on. Has anyone heard of this?

thanks,

RDave


    
This message has been edited by FairlaneCobra69 on Feb 3, 2008 1:51 PM
This message has been edited by FairlaneCobra69 on Feb 3, 2008 1:02 PM


 
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AuthorReply

Barry Byer
(Login BarryByer)
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It doesn't really make any difference

February 3 2008, 10:57 AM 

As long as you get the timing where it needs to be. What I have always done is put the #1 cylinder on TDC and drop in the distributor so it's pointing at the #1 position on the cap. Occasionally it may have to come out and move one tooth but it's not a big deal either way.
I personally like the vacuum hose to point towards the passenger side like the bottom picture but there is absolutely no logical reason for that!


53 F100, Volare clip, 4 wheel disc soon to be 390-wide ratio toploader (428 on the build)

 
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(Login 10w30dna)
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For show use it matters

February 3 2008, 11:10 AM 

As noted,it will work just fine in any position.Sounds like you are trying to do it a "right" as possible. The correct position is like in the second set of pictures. Pointing more towards the passenger's side. Just a little "quirk" of mine ! www.428cobrajetcars.homestead.com

Engines are like garages,never big enough![IMG][/IMG] Check out my distributor restoration site! http://428cobrajetcars.homestead.com

 
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(Login RichFerguson)
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Distributor position as shown in the two lower pics...

February 3 2008, 11:13 AM 

... is the correct position. That's how the distributors were installed when they rolled off the assembly line. You can install your distributor where ever you like and performance will not be affected as long as timing is set properly.

 
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(Login FairlaneCobra69)
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photos of "the other correct position"

February 3 2008, 12:02 PM 

here are a couple of photos of engines with their distributors in another position:

[img][/img]

[img][/img]

I think it would make a difference if you were off a tooth one way or another on the cam, because there are 15 teeth on the distributor, and each tooth off from the correct position would mean a difference of 24 degrees in the relationship between #1 TDC on the distributor and the cam. This would have to be made up by rotating the distributor even more. I have seen some distributors that were rotated so far clockwise, that the vacuum advance was pushed up against the waterpump bypass tube.

I still think Steve Christ's approach makes sense, in that you would have more room to rotate the distributor clockwise to advance it (unless you were more interested in retarding it!).

RDave


 
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(Login Morrisman2)
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Moving the wires, not the gear?

February 3 2008, 12:48 PM 

You could move the distributor between the two 'favorite' positions shown simply by moving the plug leads round one station, then turning the dizzy to realign the correct plug lead with the rotor position. It looks to be 60 degrees between the two.

Or you could get a half move (30ish degrees) by shifting the dizzy one tooth on the drive gear.

 
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Joel
(Login tall69)
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Installing the dizzy

February 3 2008, 12:05 PM 

Instead of TDC on the #1 cylinder, I bring the piston to TDC, and then back the motor up to about 10 degrees before TDC by reading the dampener. That way, when the car is started, the initial timing will be closer to optimum setting.

*****************************************
Joel
1970 Torino Cobra 429SCJ/4sp 4.30 Locker
472ci - 480HP\518LB-FT installed
*****************************************

 
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Spears,Bobby
(Login bspears427)

Re: Installing the dizzy

February 3 2008, 2:44 PM 

All the above options will work.You don't need a timing light or the key on to get the base timing where you want it running.If you are using a stock system,all you have to do is take a thin wrapper like what is on a cigarette. pack or even a candy bar.With single points,place it in the contacts,slowly rotate it clockwise and as soon as you can barely pull it out,lock the clamp.On dual points put it in the second set.Or with the key on,you can watch for the contacts to spark,and lock it down when it happens.That is the way we used to do it in the old days.You can set the total the same way.Mechanical dist. just hold the rotor at full advance,with a vacuum and mech. combined then you would have to use a hand vacuum pump to hold it while you set the dist.. May be too much information but couldn't help myself.

 
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